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1NAME 1NAME
2 IO::AIO - Asynchronous Input/Output 2 IO::AIO - Asynchronous/Advanced Input/Output
3 3
4SYNOPSIS 4SYNOPSIS
5 use IO::AIO; 5 use IO::AIO;
6 6
7 aio_open "/etc/passwd", O_RDONLY, 0, sub { 7 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
8 my $fh = shift 8 my $fh = shift
9 or die "/etc/passwd: $!"; 9 or die "/etc/passwd: $!";
10 ... 10 ...
11 }; 11 };
12 12
… …
24 $req->cancel; # cancel request if still in queue 24 $req->cancel; # cancel request if still in queue
25 25
26 my $grp = aio_group sub { print "all stats done\n" }; 26 my $grp = aio_group sub { print "all stats done\n" };
27 add $grp aio_stat "..." for ...; 27 add $grp aio_stat "..." for ...;
28 28
29 # AnyEvent integration
30 open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
31 my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
32
33 # Event integration
34 Event->io (fd => IO::AIO::poll_fileno,
35 poll => 'r',
36 cb => \&IO::AIO::poll_cb);
37
38 # Glib/Gtk2 integration
39 add_watch Glib::IO IO::AIO::poll_fileno,
40 in => sub { IO::AIO::poll_cb; 1 };
41
42 # Tk integration
43 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
44 readable => \&IO::AIO::poll_cb);
45
46 # Danga::Socket integration
47 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
48 \&IO::AIO::poll_cb);
49
50DESCRIPTION 29DESCRIPTION
51 This module implements asynchronous I/O using whatever means your 30 This module implements asynchronous I/O using whatever means your
52 operating system supports. 31 operating system supports. It is implemented as an interface to "libeio"
32 (<http://software.schmorp.de/pkg/libeio.html>).
53 33
54 Asynchronous means that operations that can normally block your program 34 Asynchronous means that operations that can normally block your program
55 (e.g. reading from disk) will be done asynchronously: the operation will 35 (e.g. reading from disk) will be done asynchronously: the operation will
56 still block, but you can do something else in the meantime. This is 36 still block, but you can do something else in the meantime. This is
57 extremely useful for programs that need to stay interactive even when 37 extremely useful for programs that need to stay interactive even when
… …
61 faster on a RAID volume or over NFS when you do a number of stat 41 faster on a RAID volume or over NFS when you do a number of stat
62 operations concurrently. 42 operations concurrently.
63 43
64 While most of this works on all types of file descriptors (for example 44 While most of this works on all types of file descriptors (for example
65 sockets), using these functions on file descriptors that support 45 sockets), using these functions on file descriptors that support
66 nonblocking operation (again, sockets, pipes etc.) is very inefficient 46 nonblocking operation (again, sockets, pipes etc.) is very inefficient.
67 or might not work (aio_read fails on sockets/pipes/fifos). Use an event
68 loop for that (such as the Event module): IO::AIO will naturally fit 47 Use an event loop for that (such as the EV module): IO::AIO will
69 into such an event loop itself. 48 naturally fit into such an event loop itself.
70 49
71 In this version, a number of threads are started that execute your 50 In this version, a number of threads are started that execute your
72 requests and signal their completion. You don't need thread support in 51 requests and signal their completion. You don't need thread support in
73 perl, and the threads created by this module will not be visible to 52 perl, and the threads created by this module will not be visible to
74 perl. In the future, this module might make use of the native aio 53 perl. In the future, this module might make use of the native aio
… …
76 not well-supported or restricted (GNU/Linux doesn't allow them on normal 55 not well-supported or restricted (GNU/Linux doesn't allow them on normal
77 files currently, for example), and they would only support aio_read and 56 files currently, for example), and they would only support aio_read and
78 aio_write, so the remaining functionality would have to be implemented 57 aio_write, so the remaining functionality would have to be implemented
79 using threads anyway. 58 using threads anyway.
80 59
60 In addition to asynchronous I/O, this module also exports some rather
61 arcane interfaces, such as "madvise" or linux's "splice" system call,
62 which is why the "A" in "AIO" can also mean *advanced*.
63
81 Although the module will work with in the presence of other (Perl-) 64 Although the module will work in the presence of other (Perl-) threads,
82 threads, it is currently not reentrant in any way, so use appropriate 65 it is currently not reentrant in any way, so use appropriate locking
83 locking yourself, always call "poll_cb" from within the same thread, or 66 yourself, always call "poll_cb" from within the same thread, or never
84 never call "poll_cb" (or other "aio_" functions) recursively. 67 call "poll_cb" (or other "aio_" functions) recursively.
85 68
86 EXAMPLE 69 EXAMPLE
87 This is a simple example that uses the Event module and loads 70 This is a simple example that uses the EV module and loads /etc/passwd
88 /etc/passwd asynchronously: 71 asynchronously:
89 72
90 use Fcntl;
91 use Event; 73 use EV;
92 use IO::AIO; 74 use IO::AIO;
93 75
94 # register the IO::AIO callback with Event 76 # register the IO::AIO callback with EV
95 Event->io (fd => IO::AIO::poll_fileno, 77 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
96 poll => 'r',
97 cb => \&IO::AIO::poll_cb);
98 78
99 # queue the request to open /etc/passwd 79 # queue the request to open /etc/passwd
100 aio_open "/etc/passwd", O_RDONLY, 0, sub { 80 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
101 my $fh = shift 81 my $fh = shift
102 or die "error while opening: $!"; 82 or die "error while opening: $!";
103 83
104 # stat'ing filehandles is generally non-blocking 84 # stat'ing filehandles is generally non-blocking
105 my $size = -s $fh; 85 my $size = -s $fh;
… …
114 94
115 # file contents now in $contents 95 # file contents now in $contents
116 print $contents; 96 print $contents;
117 97
118 # exit event loop and program 98 # exit event loop and program
119 Event::unloop; 99 EV::break;
120 }; 100 };
121 }; 101 };
122 102
123 # possibly queue up other requests, or open GUI windows, 103 # possibly queue up other requests, or open GUI windows,
124 # check for sockets etc. etc. 104 # check for sockets etc. etc.
125 105
126 # process events as long as there are some: 106 # process events as long as there are some:
127 Event::loop; 107 EV::run;
128 108
129REQUEST ANATOMY AND LIFETIME 109REQUEST ANATOMY AND LIFETIME
130 Every "aio_*" function creates a request. which is a C data structure 110 Every "aio_*" function creates a request. which is a C data structure
131 not directly visible to Perl. 111 not directly visible to Perl.
132 112
… …
168 anymore (except possibly for the Perl object, but its connection to 148 anymore (except possibly for the Perl object, but its connection to
169 the actual aio request is severed and calling its methods will 149 the actual aio request is severed and calling its methods will
170 either do nothing or result in a runtime error). 150 either do nothing or result in a runtime error).
171 151
172FUNCTIONS 152FUNCTIONS
173 AIO REQUEST FUNCTIONS 153 QUICK OVERVIEW
154 This section simply lists the prototypes most of the functions for quick
155 reference. See the following sections for function-by-function
156 documentation.
157
158 aio_wd $pathname, $callback->($wd)
159 aio_open $pathname, $flags, $mode, $callback->($fh)
160 aio_close $fh, $callback->($status)
161 aio_seek $fh,$offset,$whence, $callback->($offs)
162 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
163 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
164 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
165 aio_readahead $fh,$offset,$length, $callback->($retval)
166 aio_stat $fh_or_path, $callback->($status)
167 aio_lstat $fh, $callback->($status)
168 aio_statvfs $fh_or_path, $callback->($statvfs)
169 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
170 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
171 aio_chmod $fh_or_path, $mode, $callback->($status)
172 aio_truncate $fh_or_path, $offset, $callback->($status)
173 aio_allocate $fh, $mode, $offset, $len, $callback->($status)
174 aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
175 aio_unlink $pathname, $callback->($status)
176 aio_mknod $pathname, $mode, $dev, $callback->($status)
177 aio_link $srcpath, $dstpath, $callback->($status)
178 aio_symlink $srcpath, $dstpath, $callback->($status)
179 aio_readlink $pathname, $callback->($link)
180 aio_realpath $pathname, $callback->($path)
181 aio_rename $srcpath, $dstpath, $callback->($status)
182 aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
183 aio_mkdir $pathname, $mode, $callback->($status)
184 aio_rmdir $pathname, $callback->($status)
185 aio_readdir $pathname, $callback->($entries)
186 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
187 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
188 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
189 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
190 aio_load $pathname, $data, $callback->($status)
191 aio_copy $srcpath, $dstpath, $callback->($status)
192 aio_move $srcpath, $dstpath, $callback->($status)
193 aio_rmtree $pathname, $callback->($status)
194 aio_fcntl $fh, $cmd, $arg, $callback->($status)
195 aio_ioctl $fh, $request, $buf, $callback->($status)
196 aio_sync $callback->($status)
197 aio_syncfs $fh, $callback->($status)
198 aio_fsync $fh, $callback->($status)
199 aio_fdatasync $fh, $callback->($status)
200 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
201 aio_pathsync $pathname, $callback->($status)
202 aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
203 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
204 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
205 aio_mlockall $flags, $callback->($status)
206 aio_group $callback->(...)
207 aio_nop $callback->()
208
209 $prev_pri = aioreq_pri [$pri]
210 aioreq_nice $pri_adjust
211
212 IO::AIO::poll_wait
213 IO::AIO::poll_cb
214 IO::AIO::poll
215 IO::AIO::flush
216 IO::AIO::max_poll_reqs $nreqs
217 IO::AIO::max_poll_time $seconds
218 IO::AIO::min_parallel $nthreads
219 IO::AIO::max_parallel $nthreads
220 IO::AIO::max_idle $nthreads
221 IO::AIO::idle_timeout $seconds
222 IO::AIO::max_outstanding $maxreqs
223 IO::AIO::nreqs
224 IO::AIO::nready
225 IO::AIO::npending
226 IO::AIO::reinit
227
228 $nfd = IO::AIO::get_fdlimit
229 IO::AIO::min_fdlimit $nfd
230
231 IO::AIO::sendfile $ofh, $ifh, $offset, $count
232 IO::AIO::fadvise $fh, $offset, $len, $advice
233 IO::AIO::fexecve $fh, $argv, $envp
234
235 IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
236 IO::AIO::munmap $scalar
237 IO::AIO::mremap $scalar, $new_length, $flags[, $new_address]
238 IO::AIO::madvise $scalar, $offset, $length, $advice
239 IO::AIO::mprotect $scalar, $offset, $length, $protect
240 IO::AIO::munlock $scalar, $offset = 0, $length = undef
241 IO::AIO::munlockall
242
243 # stat extensions
244 $counter = IO::AIO::st_gen
245 $seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime, IO::AIO::st_btime
246 ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
247 $nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec, IO::AIO::st_ctimensec, IO::AIO::st_btimensec
248 $seconds = IO::AIO::st_btimesec
249 ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
250
251 # very much unportable syscalls
252 IO::AIO::accept4 $r_fh, $sockaddr, $sockaddr_len, $flags
253 IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
254 IO::AIO::tee $r_fh, $w_fh, $length, $flags
255
256 $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
257 ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
258
259 $fh = IO::AIO::eventfd [$initval, [$flags]]
260 $fh = IO::AIO::memfd_create $pathname[, $flags]
261
262 $fh = IO::AIO::timerfd_create $clockid[, $flags]
263 ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
264 ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
265
266 $fh = IO::AIO::pidfd_open $pid[, $flags]
267 $status = IO::AIO::pidfd_send_signal $pidfh, $signal[, $siginfo[, $flags]]
268 $fh = IO::AIO::pidfd_getfd $pidfh, $targetfd[, $flags]
269
270 API NOTES
174 All the "aio_*" calls are more or less thin wrappers around the syscall 271 All the "aio_*" calls are more or less thin wrappers around the syscall
175 with the same name (sans "aio_"). The arguments are similar or 272 with the same name (sans "aio_"). The arguments are similar or
176 identical, and they all accept an additional (and optional) $callback 273 identical, and they all accept an additional (and optional) $callback
177 argument which must be a code reference. This code reference will get 274 argument which must be a code reference. This code reference will be
178 called with the syscall return code (e.g. most syscalls return -1 on 275 called after the syscall has been executed in an asynchronous fashion.
179 error, unlike perl, which usually delivers "false") as it's sole 276 The results of the request will be passed as arguments to the callback
180 argument when the given syscall has been executed asynchronously. 277 (and, if an error occured, in $!) - for most requests the syscall return
278 code (e.g. most syscalls return -1 on error, unlike perl, which usually
279 delivers "false").
280
281 Some requests (such as "aio_readdir") pass the actual results and
282 communicate failures by passing "undef".
181 283
182 All functions expecting a filehandle keep a copy of the filehandle 284 All functions expecting a filehandle keep a copy of the filehandle
183 internally until the request has finished. 285 internally until the request has finished.
184 286
185 All functions return request objects of type IO::AIO::REQ that allow 287 All functions return request objects of type IO::AIO::REQ that allow
186 further manipulation of those requests while they are in-flight. 288 further manipulation of those requests while they are in-flight.
187 289
188 The pathnames you pass to these routines *must* be absolute and encoded 290 The pathnames you pass to these routines *should* be absolute. The
189 as octets. The reason for the former is that at the time the request is 291 reason for this is that at the time the request is being executed, the
190 being executed, the current working directory could have changed. 292 current working directory could have changed. Alternatively, you can
191 Alternatively, you can make sure that you never change the current 293 make sure that you never change the current working directory anywhere
192 working directory anywhere in the program and then use relative paths. 294 in the program and then use relative paths. You can also take advantage
295 of IO::AIOs working directory abstraction, that lets you specify paths
296 relative to some previously-opened "working directory object" - see the
297 description of the "IO::AIO::WD" class later in this document.
193 298
194 To encode pathnames as octets, either make sure you either: a) always 299 To encode pathnames as octets, either make sure you either: a) always
195 pass in filenames you got from outside (command line, readdir etc.) 300 pass in filenames you got from outside (command line, readdir etc.)
196 without tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module 301 without tinkering, b) are in your native filesystem encoding, c) use the
197 and encode your pathnames to the locale (or other) encoding in effect in 302 Encode module and encode your pathnames to the locale (or other)
198 the user environment, d) use Glib::filename_from_unicode on unicode 303 encoding in effect in the user environment, d) use
199 filenames or e) use something else to ensure your scalar has the correct 304 Glib::filename_from_unicode on unicode filenames or e) use something
200 contents. 305 else to ensure your scalar has the correct contents.
201 306
202 This works, btw. independent of the internal UTF-8 bit, which IO::AIO 307 This works, btw. independent of the internal UTF-8 bit, which IO::AIO
203 handles correctly wether it is set or not. 308 handles correctly whether it is set or not.
204 309
310 AIO REQUEST FUNCTIONS
205 $prev_pri = aioreq_pri [$pri] 311 $prev_pri = aioreq_pri [$pri]
206 Returns the priority value that would be used for the next request 312 Returns the priority value that would be used for the next request
207 and, if $pri is given, sets the priority for the next aio request. 313 and, if $pri is given, sets the priority for the next aio request.
208 314
209 The default priority is 0, the minimum and maximum priorities are -4 315 The default priority is 0, the minimum and maximum priorities are -4
… …
231 Similar to "aioreq_pri", but subtracts the given value from the 337 Similar to "aioreq_pri", but subtracts the given value from the
232 current priority, so the effect is cumulative. 338 current priority, so the effect is cumulative.
233 339
234 aio_open $pathname, $flags, $mode, $callback->($fh) 340 aio_open $pathname, $flags, $mode, $callback->($fh)
235 Asynchronously open or create a file and call the callback with a 341 Asynchronously open or create a file and call the callback with a
236 newly created filehandle for the file. 342 newly created filehandle for the file (or "undef" in case of an
343 error).
237 344
238 The pathname passed to "aio_open" must be absolute. See API NOTES, 345 The pathname passed to "aio_open" must be absolute. See API NOTES,
239 above, for an explanation. 346 above, for an explanation.
240 347
241 The $flags argument is a bitmask. See the "Fcntl" module for a list. 348 The $flags argument is a bitmask. See the "Fcntl" module for a list.
… …
248 will be modified by the umask in effect then the request is being 355 will be modified by the umask in effect then the request is being
249 executed, so better never change the umask. 356 executed, so better never change the umask.
250 357
251 Example: 358 Example:
252 359
253 aio_open "/etc/passwd", O_RDONLY, 0, sub { 360 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
254 if ($_[0]) { 361 if ($_[0]) {
255 print "open successful, fh is $_[0]\n"; 362 print "open successful, fh is $_[0]\n";
256 ... 363 ...
257 } else { 364 } else {
258 die "open failed: $!\n"; 365 die "open failed: $!\n";
259 } 366 }
260 }; 367 };
261 368
369 In addition to all the common open modes/flags ("O_RDONLY",
370 "O_WRONLY", "O_RDWR", "O_CREAT", "O_TRUNC", "O_EXCL" and
371 "O_APPEND"), the following POSIX and non-POSIX constants are
372 available (missing ones on your system are, as usual, 0):
373
374 "O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",
375 "O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",
376 "O_DSYNC", "O_RSYNC", "O_SYNC", "O_PATH", "O_TMPFILE", "O_TTY_INIT"
377 and "O_ACCMODE".
378
262 aio_close $fh, $callback->($status) 379 aio_close $fh, $callback->($status)
263 Asynchronously close a file and call the callback with the result 380 Asynchronously close a file and call the callback with the result
264 code. *WARNING:* although accepted, you should not pass in a perl 381 code.
265 filehandle here, as perl will likely close the file descriptor
266 another time when the filehandle is destroyed. Normally, you can
267 safely call perls "close" or just let filehandles go out of scope.
268 382
269 This is supposed to be a bug in the API, so that might change. It's 383 Unfortunately, you can't do this to perl. Perl *insists* very
270 therefore best to avoid this function. 384 strongly on closing the file descriptor associated with the
385 filehandle itself.
386
387 Therefore, "aio_close" will not close the filehandle - instead it
388 will use dup2 to overwrite the file descriptor with the write-end of
389 a pipe (the pipe fd will be created on demand and will be cached).
390
391 Or in other words: the file descriptor will be closed, but it will
392 not be free for reuse until the perl filehandle is closed.
393
394 aio_seek $fh, $offset, $whence, $callback->($offs)
395 Seeks the filehandle to the new $offset, similarly to perl's
396 "sysseek". The $whence can use the traditional values (0 for
397 "IO::AIO::SEEK_SET", 1 for "IO::AIO::SEEK_CUR" or 2 for
398 "IO::AIO::SEEK_END").
399
400 The resulting absolute offset will be passed to the callback, or -1
401 in case of an error.
402
403 In theory, the $whence constants could be different than the
404 corresponding values from Fcntl, but perl guarantees they are the
405 same, so don't panic.
406
407 As a GNU/Linux (and maybe Solaris) extension, also the constants
408 "IO::AIO::SEEK_DATA" and "IO::AIO::SEEK_HOLE" are available, if they
409 could be found. No guarantees about suitability for use in
410 "aio_seek" or Perl's "sysseek" can be made though, although I would
411 naively assume they "just work".
271 412
272 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 413 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
273 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 414 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
274 Reads or writes "length" bytes from the specified "fh" and "offset" 415 Reads or writes $length bytes from or to the specified $fh and
275 into the scalar given by "data" and offset "dataoffset" and calls 416 $offset into the scalar given by $data and offset $dataoffset and
276 the callback without the actual number of bytes read (or -1 on 417 calls the callback with the actual number of bytes transferred (or
277 error, just like the syscall). 418 -1 on error, just like the syscall).
419
420 "aio_read" will, like "sysread", shrink or grow the $data scalar to
421 offset plus the actual number of bytes read.
422
423 If $offset is undefined, then the current file descriptor offset
424 will be used (and updated), otherwise the file descriptor offset
425 will not be changed by these calls.
426
427 If $length is undefined in "aio_write", use the remaining length of
428 $data.
429
430 If $dataoffset is less than zero, it will be counted from the end of
431 $data.
278 432
279 The $data scalar *MUST NOT* be modified in any way while the request 433 The $data scalar *MUST NOT* be modified in any way while the request
280 is outstanding. Modifying it can result in segfaults or WW3 (if the 434 is outstanding. Modifying it can result in segfaults or World War
281 necessary/optional hardware is installed). 435 III (if the necessary/optional hardware is installed).
282 436
283 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at 437 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
284 offset 0 within the scalar: 438 offset 0 within the scalar:
285 439
286 aio_read $fh, 7, 15, $buffer, 0, sub { 440 aio_read $fh, 7, 15, $buffer, 0, sub {
… …
291 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 445 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
292 Tries to copy $length bytes from $in_fh to $out_fh. It starts 446 Tries to copy $length bytes from $in_fh to $out_fh. It starts
293 reading at byte offset $in_offset, and starts writing at the current 447 reading at byte offset $in_offset, and starts writing at the current
294 file offset of $out_fh. Because of that, it is not safe to issue 448 file offset of $out_fh. Because of that, it is not safe to issue
295 more than one "aio_sendfile" per $out_fh, as they will interfere 449 more than one "aio_sendfile" per $out_fh, as they will interfere
296 with each other. 450 with each other. The same $in_fh works fine though, as this function
451 does not move or use the file offset of $in_fh.
297 452
453 Please note that "aio_sendfile" can read more bytes from $in_fh than
454 are written, and there is no way to find out how many more bytes
455 have been read from "aio_sendfile" alone, as "aio_sendfile" only
456 provides the number of bytes written to $out_fh. Only if the result
457 value equals $length one can assume that $length bytes have been
458 read.
459
460 Unlike with other "aio_" functions, it makes a lot of sense to use
461 "aio_sendfile" on non-blocking sockets, as long as one end
462 (typically the $in_fh) is a file - the file I/O will then be
463 asynchronous, while the socket I/O will be non-blocking. Note,
464 however, that you can run into a trap where "aio_sendfile" reads
465 some data with readahead, then fails to write all data, and when the
466 socket is ready the next time, the data in the cache is already
467 lost, forcing "aio_sendfile" to again hit the disk. Explicit
468 "aio_read" + "aio_write" let's you better control resource usage.
469
298 This call tries to make use of a native "sendfile" syscall to 470 This call tries to make use of a native "sendfile"-like syscall to
299 provide zero-copy operation. For this to work, $out_fh should refer 471 provide zero-copy operation. For this to work, $out_fh should refer
300 to a socket, and $in_fh should refer to mmap'able file. 472 to a socket, and $in_fh should refer to an mmap'able file.
301 473
302 If the native sendfile call fails or is not implemented, it will be 474 If a native sendfile cannot be found or it fails with "ENOSYS",
303 emulated, so you can call "aio_sendfile" on any type of filehandle 475 "EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
304 regardless of the limitations of the operating system. 476 "ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on
477 any type of filehandle regardless of the limitations of the
478 operating system.
305 479
306 Please note, however, that "aio_sendfile" can read more bytes from 480 As native sendfile syscalls (as practically any non-POSIX interface
307 $in_fh than are written, and there is no way to find out how many 481 hacked together in a hurry to improve benchmark numbers) tend to be
308 bytes have been read from "aio_sendfile" alone, as "aio_sendfile" 482 rather buggy on many systems, this implementation tries to work
309 only provides the number of bytes written to $out_fh. Only if the 483 around some known bugs in Linux and FreeBSD kernels (probably
310 result value equals $length one can assume that $length bytes have 484 others, too), but that might fail, so you really really should check
311 been read. 485 the return value of "aio_sendfile" - fewer bytes than expected might
486 have been transferred.
312 487
313 aio_readahead $fh,$offset,$length, $callback->($retval) 488 aio_readahead $fh,$offset,$length, $callback->($retval)
314 "aio_readahead" populates the page cache with data from a file so 489 "aio_readahead" populates the page cache with data from a file so
315 that subsequent reads from that file will not block on disk I/O. The 490 that subsequent reads from that file will not block on disk I/O. The
316 $offset argument specifies the starting point from which data is to 491 $offset argument specifies the starting point from which data is to
… …
319 to a page boundary and bytes are read up to the next page boundary 494 to a page boundary and bytes are read up to the next page boundary
320 greater than or equal to (off-set+length). "aio_readahead" does not 495 greater than or equal to (off-set+length). "aio_readahead" does not
321 read beyond the end of the file. The current file offset of the file 496 read beyond the end of the file. The current file offset of the file
322 is left unchanged. 497 is left unchanged.
323 498
324 If that syscall doesn't exist (likely if your OS isn't Linux) it 499 If that syscall doesn't exist (likely if your kernel isn't Linux) it
325 will be emulated by simply reading the data, which would have a 500 will be emulated by simply reading the data, which would have a
326 similar effect. 501 similar effect.
327 502
328 aio_stat $fh_or_path, $callback->($status) 503 aio_stat $fh_or_path, $callback->($status)
329 aio_lstat $fh, $callback->($status) 504 aio_lstat $fh, $callback->($status)
330 Works like perl's "stat" or "lstat" in void context. The callback 505 Works almost exactly like perl's "stat" or "lstat" in void context.
331 will be called after the stat and the results will be available 506 The callback will be called after the stat and the results will be
332 using "stat _" or "-s _" etc... 507 available using "stat _" or "-s _" and other tests (with the
508 exception of "-B" and "-T").
333 509
334 The pathname passed to "aio_stat" must be absolute. See API NOTES, 510 The pathname passed to "aio_stat" must be absolute. See API NOTES,
335 above, for an explanation. 511 above, for an explanation.
336 512
337 Currently, the stats are always 64-bit-stats, i.e. instead of 513 Currently, the stats are always 64-bit-stats, i.e. instead of
338 returning an error when stat'ing a large file, the results will be 514 returning an error when stat'ing a large file, the results will be
339 silently truncated unless perl itself is compiled with large file 515 silently truncated unless perl itself is compiled with large file
340 support. 516 support.
341 517
518 To help interpret the mode and dev/rdev stat values, IO::AIO offers
519 the following constants and functions (if not implemented, the
520 constants will be 0 and the functions will either "croak" or fall
521 back on traditional behaviour).
522
523 "S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
524 "S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
525 "IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
526
527 To access higher resolution stat timestamps, see "SUBSECOND STAT
528 TIME ACCESS".
529
342 Example: Print the length of /etc/passwd: 530 Example: Print the length of /etc/passwd:
343 531
344 aio_stat "/etc/passwd", sub { 532 aio_stat "/etc/passwd", sub {
345 $_[0] and die "stat failed: $!"; 533 $_[0] and die "stat failed: $!";
346 print "size is ", -s _, "\n"; 534 print "size is ", -s _, "\n";
347 }; 535 };
348 536
537 aio_statvfs $fh_or_path, $callback->($statvfs)
538 Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
539 whether a file handle or path was passed.
540
541 On success, the callback is passed a hash reference with the
542 following members: "bsize", "frsize", "blocks", "bfree", "bavail",
543 "files", "ffree", "favail", "fsid", "flag" and "namemax". On
544 failure, "undef" is passed.
545
546 The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
547 and "ST_NOSUID".
548
549 The following non-POSIX IO::AIO::ST_* flag masks are defined to
550 their correct value when available, or to 0 on systems that do not
551 support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
552 "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
553 "ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
554
555 Example: stat "/wd" and dump out the data if successful.
556
557 aio_statvfs "/wd", sub {
558 my $f = $_[0]
559 or die "statvfs: $!";
560
561 use Data::Dumper;
562 say Dumper $f;
563 };
564
565 # result:
566 {
567 bsize => 1024,
568 bfree => 4333064312,
569 blocks => 10253828096,
570 files => 2050765568,
571 flag => 4096,
572 favail => 2042092649,
573 bavail => 4333064312,
574 ffree => 2042092649,
575 namemax => 255,
576 frsize => 1024,
577 fsid => 1810
578 }
579
580 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
581 Works like perl's "utime" function (including the special case of
582 $atime and $mtime being undef). Fractional times are supported if
583 the underlying syscalls support them.
584
585 When called with a pathname, uses utimensat(2) or utimes(2) if
586 available, otherwise utime(2). If called on a file descriptor, uses
587 futimens(2) or futimes(2) if available, otherwise returns ENOSYS, so
588 this is not portable.
589
590 Examples:
591
592 # set atime and mtime to current time (basically touch(1)):
593 aio_utime "path", undef, undef;
594 # set atime to current time and mtime to beginning of the epoch:
595 aio_utime "path", time, undef; # undef==0
596
597 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
598 Works like perl's "chown" function, except that "undef" for either
599 $uid or $gid is being interpreted as "do not change" (but -1 can
600 also be used).
601
602 Examples:
603
604 # same as "chown root path" in the shell:
605 aio_chown "path", 0, -1;
606 # same as above:
607 aio_chown "path", 0, undef;
608
609 aio_truncate $fh_or_path, $offset, $callback->($status)
610 Works like truncate(2) or ftruncate(2).
611
612 aio_allocate $fh, $mode, $offset, $len, $callback->($status)
613 Allocates or frees disk space according to the $mode argument. See
614 the linux "fallocate" documentation for details.
615
616 $mode is usually 0 or "IO::AIO::FALLOC_FL_KEEP_SIZE" to allocate
617 space, or "IO::AIO::FALLOC_FL_PUNCH_HOLE |
618 IO::AIO::FALLOC_FL_KEEP_SIZE", to deallocate a file range.
619
620 IO::AIO also supports "FALLOC_FL_COLLAPSE_RANGE", to remove a range
621 (without leaving a hole), "FALLOC_FL_ZERO_RANGE", to zero a range,
622 "FALLOC_FL_INSERT_RANGE" to insert a range and
623 "FALLOC_FL_UNSHARE_RANGE" to unshare shared blocks (see your
624 fallocate(2) manpage).
625
626 The file system block size used by "fallocate" is presumably the
627 "f_bsize" returned by "statvfs", but different filesystems and
628 filetypes can dictate other limitations.
629
630 If "fallocate" isn't available or cannot be emulated (currently no
631 emulation will be attempted), passes -1 and sets $! to "ENOSYS".
632
633 aio_chmod $fh_or_path, $mode, $callback->($status)
634 Works like perl's "chmod" function.
635
349 aio_unlink $pathname, $callback->($status) 636 aio_unlink $pathname, $callback->($status)
350 Asynchronously unlink (delete) a file and call the callback with the 637 Asynchronously unlink (delete) a file and call the callback with the
351 result code. 638 result code.
352 639
353 aio_mknod $path, $mode, $dev, $callback->($status) 640 aio_mknod $pathname, $mode, $dev, $callback->($status)
354 [EXPERIMENTAL] 641 [EXPERIMENTAL]
355 642
356 Asynchronously create a device node (or fifo). See mknod(2). 643 Asynchronously create a device node (or fifo). See mknod(2).
357 644
358 The only (POSIX-) portable way of calling this function is: 645 The only (POSIX-) portable way of calling this function is:
359 646
360 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... 647 aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
648
649 See "aio_stat" for info about some potentially helpful extra
650 constants and functions.
361 651
362 aio_link $srcpath, $dstpath, $callback->($status) 652 aio_link $srcpath, $dstpath, $callback->($status)
363 Asynchronously create a new link to the existing object at $srcpath 653 Asynchronously create a new link to the existing object at $srcpath
364 at the path $dstpath and call the callback with the result code. 654 at the path $dstpath and call the callback with the result code.
365 655
366 aio_symlink $srcpath, $dstpath, $callback->($status) 656 aio_symlink $srcpath, $dstpath, $callback->($status)
367 Asynchronously create a new symbolic link to the existing object at 657 Asynchronously create a new symbolic link to the existing object at
368 $srcpath at the path $dstpath and call the callback with the result 658 $srcpath at the path $dstpath and call the callback with the result
369 code. 659 code.
370 660
371 aio_readlink $path, $callback->($link) 661 aio_readlink $pathname, $callback->($link)
372 Asynchronously read the symlink specified by $path and pass it to 662 Asynchronously read the symlink specified by $path and pass it to
373 the callback. If an error occurs, nothing or undef gets passed to 663 the callback. If an error occurs, nothing or undef gets passed to
374 the callback. 664 the callback.
375 665
666 aio_realpath $pathname, $callback->($path)
667 Asynchronously make the path absolute and resolve any symlinks in
668 $path. The resulting path only consists of directories (same as
669 Cwd::realpath).
670
671 This request can be used to get the absolute path of the current
672 working directory by passing it a path of . (a single dot).
673
376 aio_rename $srcpath, $dstpath, $callback->($status) 674 aio_rename $srcpath, $dstpath, $callback->($status)
377 Asynchronously rename the object at $srcpath to $dstpath, just as 675 Asynchronously rename the object at $srcpath to $dstpath, just as
378 rename(2) and call the callback with the result code. 676 rename(2) and call the callback with the result code.
677
678 On systems that support the AIO::WD working directory abstraction
679 natively, the case "[$wd, "."]" as $srcpath is specialcased -
680 instead of failing, "rename" is called on the absolute path of $wd.
681
682 aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
683 Basically a version of "aio_rename" with an additional $flags
684 argument. Calling this with "$flags=0" is the same as calling
685 "aio_rename".
686
687 Non-zero flags are currently only supported on GNU/Linux systems
688 that support renameat2. Other systems fail with "ENOSYS" in this
689 case.
690
691 The following constants are available (missing ones are, as usual
692 0), see renameat2(2) for details:
693
694 "IO::AIO::RENAME_NOREPLACE", "IO::AIO::RENAME_EXCHANGE" and
695 "IO::AIO::RENAME_WHITEOUT".
379 696
380 aio_mkdir $pathname, $mode, $callback->($status) 697 aio_mkdir $pathname, $mode, $callback->($status)
381 Asynchronously mkdir (create) a directory and call the callback with 698 Asynchronously mkdir (create) a directory and call the callback with
382 the result code. $mode will be modified by the umask at the time the 699 the result code. $mode will be modified by the umask at the time the
383 request is executed, so do not change your umask. 700 request is executed, so do not change your umask.
384 701
385 aio_rmdir $pathname, $callback->($status) 702 aio_rmdir $pathname, $callback->($status)
386 Asynchronously rmdir (delete) a directory and call the callback with 703 Asynchronously rmdir (delete) a directory and call the callback with
387 the result code. 704 the result code.
388 705
706 On systems that support the AIO::WD working directory abstraction
707 natively, the case "[$wd, "."]" is specialcased - instead of
708 failing, "rmdir" is called on the absolute path of $wd.
709
389 aio_readdir $pathname, $callback->($entries) 710 aio_readdir $pathname, $callback->($entries)
390 Unlike the POSIX call of the same name, "aio_readdir" reads an 711 Unlike the POSIX call of the same name, "aio_readdir" reads an
391 entire directory (i.e. opendir + readdir + closedir). The entries 712 entire directory (i.e. opendir + readdir + closedir). The entries
392 will not be sorted, and will NOT include the "." and ".." entries. 713 will not be sorted, and will NOT include the "." and ".." entries.
393 714
394 The callback a single argument which is either "undef" or an 715 The callback is passed a single argument which is either "undef" or
395 array-ref with the filenames. 716 an array-ref with the filenames.
396 717
718 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
719 Quite similar to "aio_readdir", but the $flags argument allows one
720 to tune behaviour and output format. In case of an error, $entries
721 will be "undef".
722
723 The flags are a combination of the following constants, ORed
724 together (the flags will also be passed to the callback, possibly
725 modified):
726
727 IO::AIO::READDIR_DENTS
728 Normally the callback gets an arrayref consisting of names only
729 (as with "aio_readdir"). If this flag is set, then the callback
730 gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
731 describing a single directory entry in more detail:
732
733 $name is the name of the entry.
734
735 $type is one of the "IO::AIO::DT_xxx" constants:
736
737 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
738 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
739 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
740
741 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
742 you need to know, you have to run stat yourself. Also, for
743 speed/memory reasons, the $type scalars are read-only: you must
744 not modify them.
745
746 $inode is the inode number (which might not be exact on systems
747 with 64 bit inode numbers and 32 bit perls). This field has
748 unspecified content on systems that do not deliver the inode
749 information.
750
751 IO::AIO::READDIR_DIRS_FIRST
752 When this flag is set, then the names will be returned in an
753 order where likely directories come first, in optimal stat
754 order. This is useful when you need to quickly find directories,
755 or you want to find all directories while avoiding to stat()
756 each entry.
757
758 If the system returns type information in readdir, then this is
759 used to find directories directly. Otherwise, likely directories
760 are names beginning with ".", or otherwise names with no dots,
761 of which names with short names are tried first.
762
763 IO::AIO::READDIR_STAT_ORDER
764 When this flag is set, then the names will be returned in an
765 order suitable for stat()'ing each one. That is, when you plan
766 to stat() most or all files in the given directory, then the
767 returned order will likely be faster.
768
769 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
770 specified, then the likely dirs come first, resulting in a less
771 optimal stat order for stat'ing all entries, but likely a more
772 optimal order for finding subdirectories.
773
774 IO::AIO::READDIR_FOUND_UNKNOWN
775 This flag should not be set when calling "aio_readdirx".
776 Instead, it is being set by "aio_readdirx", when any of the
777 $type's found were "IO::AIO::DT_UNKNOWN". The absence of this
778 flag therefore indicates that all $type's are known, which can
779 be used to speed up some algorithms.
780
781 aio_slurp $pathname, $offset, $length, $data, $callback->($status)
782 Opens, reads and closes the given file. The data is put into $data,
783 which is resized as required.
784
785 If $offset is negative, then it is counted from the end of the file.
786
787 If $length is zero, then the remaining length of the file is used.
788 Also, in this case, the same limitations to modifying $data apply as
789 when IO::AIO::mmap is used, i.e. it must only be modified in-place
790 with "substr". If the size of the file is known, specifying a
791 non-zero $length results in a performance advantage.
792
793 This request is similar to the older "aio_load" request, but since
794 it is a single request, it might be more efficient to use.
795
796 Example: load /etc/passwd into $passwd.
797
798 my $passwd;
799 aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
800 $_[0] >= 0
801 or die "/etc/passwd: $!\n";
802
803 printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
804 print $passwd;
805 };
806 IO::AIO::flush;
807
397 aio_load $path, $data, $callback->($status) 808 aio_load $pathname, $data, $callback->($status)
398 This is a composite request that tries to fully load the given file 809 This is a composite request that tries to fully load the given file
399 into memory. Status is the same as with aio_read. 810 into memory. Status is the same as with aio_read.
811
812 Using "aio_slurp" might be more efficient, as it is a single
813 request.
400 814
401 aio_copy $srcpath, $dstpath, $callback->($status) 815 aio_copy $srcpath, $dstpath, $callback->($status)
402 Try to copy the *file* (directories not supported as either source 816 Try to copy the *file* (directories not supported as either source
403 or destination) from $srcpath to $dstpath and call the callback with 817 or destination) from $srcpath to $dstpath and call the callback with
404 the 0 (error) or -1 ok. 818 a status of 0 (ok) or -1 (error, see $!).
405 819
820 Existing destination files will be truncated.
821
406 This is a composite request that it creates the destination file 822 This is a composite request that creates the destination file with
407 with mode 0200 and copies the contents of the source file into it 823 mode 0200 and copies the contents of the source file into it using
408 using "aio_sendfile", followed by restoring atime, mtime, access 824 "aio_sendfile", followed by restoring atime, mtime, access mode and
409 mode and uid/gid, in that order. 825 uid/gid, in that order.
410 826
411 If an error occurs, the partial destination file will be unlinked, 827 If an error occurs, the partial destination file will be unlinked,
412 if possible, except when setting atime, mtime, access mode and 828 if possible, except when setting atime, mtime, access mode and
413 uid/gid, where errors are being ignored. 829 uid/gid, where errors are being ignored.
414 830
415 aio_move $srcpath, $dstpath, $callback->($status) 831 aio_move $srcpath, $dstpath, $callback->($status)
416 Try to move the *file* (directories not supported as either source 832 Try to move the *file* (directories not supported as either source
417 or destination) from $srcpath to $dstpath and call the callback with 833 or destination) from $srcpath to $dstpath and call the callback with
418 the 0 (error) or -1 ok. 834 a status of 0 (ok) or -1 (error, see $!).
419 835
420 This is a composite request that tries to rename(2) the file first. 836 This is a composite request that tries to rename(2) the file first;
421 If rename files with "EXDEV", it copies the file with "aio_copy" 837 if rename fails with "EXDEV", it copies the file with "aio_copy"
422 and, if that is successful, unlinking the $srcpath. 838 and, if that is successful, unlinks the $srcpath.
423 839
424 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 840 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
425 Scans a directory (similar to "aio_readdir") but additionally tries 841 Scans a directory (similar to "aio_readdir") but additionally tries
426 to efficiently separate the entries of directory $path into two sets 842 to efficiently separate the entries of directory $path into two sets
427 of names, directories you can recurse into (directories), and ones 843 of names, directories you can recurse into (directories), and ones
428 you cannot recurse into (everything else, including symlinks to 844 you cannot recurse into (everything else, including symlinks to
429 directories). 845 directories).
430 846
431 "aio_scandir" is a composite request that creates of many sub 847 "aio_scandir" is a composite request that generates many sub
432 requests_ $maxreq specifies the maximum number of outstanding aio 848 requests. $maxreq specifies the maximum number of outstanding aio
433 requests that this function generates. If it is "<= 0", then a 849 requests that this function generates. If it is "<= 0", then a
434 suitable default will be chosen (currently 4). 850 suitable default will be chosen (currently 4).
435 851
436 On error, the callback is called without arguments, otherwise it 852 On error, the callback is called without arguments, otherwise it
437 receives two array-refs with path-relative entry names. 853 receives two array-refs with path-relative entry names.
… …
447 Implementation notes. 863 Implementation notes.
448 864
449 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry 865 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
450 can. 866 can.
451 867
868 If readdir returns file type information, then this is used directly
869 to find directories.
870
452 After reading the directory, the modification time, size etc. of the 871 Otherwise, after reading the directory, the modification time, size
453 directory before and after the readdir is checked, and if they match 872 etc. of the directory before and after the readdir is checked, and
454 (and isn't the current time), the link count will be used to decide 873 if they match (and isn't the current time), the link count will be
455 how many entries are directories (if >= 2). Otherwise, no knowledge 874 used to decide how many entries are directories (if >= 2).
456 of the number of subdirectories will be assumed. 875 Otherwise, no knowledge of the number of subdirectories will be
876 assumed.
457 877
458 Then entries will be sorted into likely directories (everything 878 Then entries will be sorted into likely directories a non-initial
459 without a non-initial dot currently) and likely non-directories 879 dot currently) and likely non-directories (see "aio_readdirx"). Then
460 (everything else). Then every entry plus an appended "/." will be 880 every entry plus an appended "/." will be "stat"'ed, likely
461 "stat"'ed, likely directories first. If that succeeds, it assumes 881 directories first, in order of their inode numbers. If that
462 that the entry is a directory or a symlink to directory (which will 882 succeeds, it assumes that the entry is a directory or a symlink to
463 be checked seperately). This is often faster than stat'ing the entry 883 directory (which will be checked separately). This is often faster
464 itself because filesystems might detect the type of the entry 884 than stat'ing the entry itself because filesystems might detect the
465 without reading the inode data (e.g. ext2fs filetype feature). 885 type of the entry without reading the inode data (e.g. ext2fs
886 filetype feature), even on systems that cannot return the filetype
887 information on readdir.
466 888
467 If the known number of directories (link count - 2) has been 889 If the known number of directories (link count - 2) has been
468 reached, the rest of the entries is assumed to be non-directories. 890 reached, the rest of the entries is assumed to be non-directories.
469 891
470 This only works with certainty on POSIX (= UNIX) filesystems, which 892 This only works with certainty on POSIX (= UNIX) filesystems, which
… …
472 894
473 It will also likely work on non-POSIX filesystems with reduced 895 It will also likely work on non-POSIX filesystems with reduced
474 efficiency as those tend to return 0 or 1 as link counts, which 896 efficiency as those tend to return 0 or 1 as link counts, which
475 disables the directory counting heuristic. 897 disables the directory counting heuristic.
476 898
477 aio_rmtree $path, $callback->($status) 899 aio_rmtree $pathname, $callback->($status)
478 Delete a directory tree starting (and including) $path, return the 900 Delete a directory tree starting (and including) $path, return the
479 status of the final "rmdir" only. This is a composite request that 901 status of the final "rmdir" only. This is a composite request that
480 uses "aio_scandir" to recurse into and rmdir directories, and unlink 902 uses "aio_scandir" to recurse into and rmdir directories, and unlink
481 everything else. 903 everything else.
482 904
905 aio_fcntl $fh, $cmd, $arg, $callback->($status)
906 aio_ioctl $fh, $request, $buf, $callback->($status)
907 These work just like the "fcntl" and "ioctl" built-in functions,
908 except they execute asynchronously and pass the return value to the
909 callback.
910
911 Both calls can be used for a lot of things, some of which make more
912 sense to run asynchronously in their own thread, while some others
913 make less sense. For example, calls that block waiting for external
914 events, such as locking, will also lock down an I/O thread while it
915 is waiting, which can deadlock the whole I/O system. At the same
916 time, there might be no alternative to using a thread to wait.
917
918 So in general, you should only use these calls for things that do
919 (filesystem) I/O, not for things that wait for other events
920 (network, other processes), although if you are careful and know
921 what you are doing, you still can.
922
923 The following constants are available and can be used for normal
924 "ioctl" and "fcntl" as well (missing ones are, as usual 0):
925
926 "F_DUPFD_CLOEXEC",
927
928 "F_OFD_GETLK", "F_OFD_SETLK", "F_OFD_GETLKW",
929
930 "FIFREEZE", "FITHAW", "FITRIM", "FICLONE", "FICLONERANGE",
931 "FIDEDUPERANGE".
932
933 "F_ADD_SEALS", "F_GET_SEALS", "F_SEAL_SEAL", "F_SEAL_SHRINK",
934 "F_SEAL_GROW" and "F_SEAL_WRITE".
935
936 "FS_IOC_GETFLAGS", "FS_IOC_SETFLAGS", "FS_IOC_GETVERSION",
937 "FS_IOC_SETVERSION", "FS_IOC_FIEMAP".
938
939 "FS_IOC_FSGETXATTR", "FS_IOC_FSSETXATTR",
940 "FS_IOC_SET_ENCRYPTION_POLICY", "FS_IOC_GET_ENCRYPTION_PWSALT",
941 "FS_IOC_GET_ENCRYPTION_POLICY", "FS_KEY_DESCRIPTOR_SIZE".
942
943 "FS_SECRM_FL", "FS_UNRM_FL", "FS_COMPR_FL", "FS_SYNC_FL",
944 "FS_IMMUTABLE_FL", "FS_APPEND_FL", "FS_NODUMP_FL", "FS_NOATIME_FL",
945 "FS_DIRTY_FL", "FS_COMPRBLK_FL", "FS_NOCOMP_FL", "FS_ENCRYPT_FL",
946 "FS_BTREE_FL", "FS_INDEX_FL", "FS_JOURNAL_DATA_FL", "FS_NOTAIL_FL",
947 "FS_DIRSYNC_FL", "FS_TOPDIR_FL", "FS_FL_USER_MODIFIABLE".
948
949 "FS_XFLAG_REALTIME", "FS_XFLAG_PREALLOC", "FS_XFLAG_IMMUTABLE",
950 "FS_XFLAG_APPEND", "FS_XFLAG_SYNC", "FS_XFLAG_NOATIME",
951 "FS_XFLAG_NODUMP", "FS_XFLAG_RTINHERIT", "FS_XFLAG_PROJINHERIT",
952 "FS_XFLAG_NOSYMLINKS", "FS_XFLAG_EXTSIZE", "FS_XFLAG_EXTSZINHERIT",
953 "FS_XFLAG_NODEFRAG", "FS_XFLAG_FILESTREAM", "FS_XFLAG_DAX",
954 "FS_XFLAG_HASATTR",
955
956 aio_sync $callback->($status)
957 Asynchronously call sync and call the callback when finished.
958
483 aio_fsync $fh, $callback->($status) 959 aio_fsync $fh, $callback->($status)
484 Asynchronously call fsync on the given filehandle and call the 960 Asynchronously call fsync on the given filehandle and call the
485 callback with the fsync result code. 961 callback with the fsync result code.
486 962
487 aio_fdatasync $fh, $callback->($status) 963 aio_fdatasync $fh, $callback->($status)
488 Asynchronously call fdatasync on the given filehandle and call the 964 Asynchronously call fdatasync on the given filehandle and call the
489 callback with the fdatasync result code. 965 callback with the fdatasync result code.
490 966
491 If this call isn't available because your OS lacks it or it couldn't 967 If this call isn't available because your OS lacks it or it couldn't
492 be detected, it will be emulated by calling "fsync" instead. 968 be detected, it will be emulated by calling "fsync" instead.
969
970 aio_syncfs $fh, $callback->($status)
971 Asynchronously call the syncfs syscall to sync the filesystem
972 associated to the given filehandle and call the callback with the
973 syncfs result code. If syncfs is not available, calls sync(), but
974 returns -1 and sets errno to "ENOSYS" nevertheless.
975
976 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
977 Sync the data portion of the file specified by $offset and $length
978 to disk (but NOT the metadata), by calling the Linux-specific
979 sync_file_range call. If sync_file_range is not available or it
980 returns ENOSYS, then fdatasync or fsync is being substituted.
981
982 $flags can be a combination of
983 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
984 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
985 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
986 manpage for details.
987
988 aio_pathsync $pathname, $callback->($status)
989 This request tries to open, fsync and close the given path. This is
990 a composite request intended to sync directories after directory
991 operations (E.g. rename). This might not work on all operating
992 systems or have any specific effect, but usually it makes sure that
993 directory changes get written to disc. It works for anything that
994 can be opened for read-only, not just directories.
995
996 Future versions of this function might fall back to other methods
997 when "fsync" on the directory fails (such as calling "sync").
998
999 Passes 0 when everything went ok, and -1 on error.
1000
1001 aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC,
1002 $callback->($status)
1003 This is a rather advanced IO::AIO call, which only works on
1004 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
1005 also works on data scalars managed by the Sys::Mmap or Mmap modules,
1006 note that the scalar must only be modified in-place while an aio
1007 operation is pending on it).
1008
1009 It calls the "msync" function of your OS, if available, with the
1010 memory area starting at $offset in the string and ending $length
1011 bytes later. If $length is negative, counts from the end, and if
1012 $length is "undef", then it goes till the end of the string. The
1013 flags can be either "IO::AIO::MS_ASYNC" or "IO::AIO::MS_SYNC", plus
1014 an optional "IO::AIO::MS_INVALIDATE".
1015
1016 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
1017 $callback->($status)
1018 This is a rather advanced IO::AIO call, which works best on
1019 mmap(2)ed scalars.
1020
1021 It touches (reads or writes) all memory pages in the specified range
1022 inside the scalar. All caveats and parameters are the same as for
1023 "aio_msync", above, except for flags, which must be either 0 (which
1024 reads all pages and ensures they are instantiated) or
1025 "IO::AIO::MT_MODIFY", which modifies the memory pages (by reading
1026 and writing an octet from it, which dirties the page).
1027
1028 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
1029 This is a rather advanced IO::AIO call, which works best on
1030 mmap(2)ed scalars.
1031
1032 It reads in all the pages of the underlying storage into memory (if
1033 any) and locks them, so they are not getting swapped/paged out or
1034 removed.
1035
1036 If $length is undefined, then the scalar will be locked till the
1037 end.
1038
1039 On systems that do not implement "mlock", this function returns -1
1040 and sets errno to "ENOSYS".
1041
1042 Note that the corresponding "munlock" is synchronous and is
1043 documented under "MISCELLANEOUS FUNCTIONS".
1044
1045 Example: open a file, mmap and mlock it - both will be undone when
1046 $data gets destroyed.
1047
1048 open my $fh, "<", $path or die "$path: $!";
1049 my $data;
1050 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
1051 aio_mlock $data; # mlock in background
1052
1053 aio_mlockall $flags, $callback->($status)
1054 Calls the "mlockall" function with the given $flags (a combination
1055 of "IO::AIO::MCL_CURRENT", "IO::AIO::MCL_FUTURE" and
1056 "IO::AIO::MCL_ONFAULT").
1057
1058 On systems that do not implement "mlockall", this function returns
1059 -1 and sets errno to "ENOSYS". Similarly, flag combinations not
1060 supported by the system result in a return value of -1 with errno
1061 being set to "EINVAL".
1062
1063 Note that the corresponding "munlockall" is synchronous and is
1064 documented under "MISCELLANEOUS FUNCTIONS".
1065
1066 Example: asynchronously lock all current and future pages into
1067 memory.
1068
1069 aio_mlockall IO::AIO::MCL_FUTURE;
1070
1071 aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
1072 Queries the extents of the given file (by calling the Linux "FIEMAP"
1073 ioctl, see <http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for
1074 details). If the ioctl is not available on your OS, then this
1075 request will fail with "ENOSYS".
1076
1077 $start is the starting offset to query extents for, $length is the
1078 size of the range to query - if it is "undef", then the whole file
1079 will be queried.
1080
1081 $flags is a combination of flags ("IO::AIO::FIEMAP_FLAG_SYNC" or
1082 "IO::AIO::FIEMAP_FLAG_XATTR" - "IO::AIO::FIEMAP_FLAGS_COMPAT" is
1083 also exported), and is normally 0 or "IO::AIO::FIEMAP_FLAG_SYNC" to
1084 query the data portion.
1085
1086 $count is the maximum number of extent records to return. If it is
1087 "undef", then IO::AIO queries all extents of the range. As a very
1088 special case, if it is 0, then the callback receives the number of
1089 extents instead of the extents themselves (which is unreliable, see
1090 below).
1091
1092 If an error occurs, the callback receives no arguments. The special
1093 "errno" value "IO::AIO::EBADR" is available to test for flag errors.
1094
1095 Otherwise, the callback receives an array reference with extent
1096 structures. Each extent structure is an array reference itself, with
1097 the following members:
1098
1099 [$logical, $physical, $length, $flags]
1100
1101 Flags is any combination of the following flag values (typically
1102 either 0 or "IO::AIO::FIEMAP_EXTENT_LAST" (1)):
1103
1104 "IO::AIO::FIEMAP_EXTENT_LAST", "IO::AIO::FIEMAP_EXTENT_UNKNOWN",
1105 "IO::AIO::FIEMAP_EXTENT_DELALLOC", "IO::AIO::FIEMAP_EXTENT_ENCODED",
1106 "IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED",
1107 "IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED",
1108 "IO::AIO::FIEMAP_EXTENT_DATA_INLINE",
1109 "IO::AIO::FIEMAP_EXTENT_DATA_TAIL",
1110 "IO::AIO::FIEMAP_EXTENT_UNWRITTEN", "IO::AIO::FIEMAP_EXTENT_MERGED"
1111 or "IO::AIO::FIEMAP_EXTENT_SHARED".
1112
1113 At the time of this writing (Linux 3.2), this request is unreliable
1114 unless $count is "undef", as the kernel has all sorts of bugs
1115 preventing it to return all extents of a range for files with a
1116 large number of extents. The code (only) works around all these
1117 issues if $count is "undef".
493 1118
494 aio_group $callback->(...) 1119 aio_group $callback->(...)
495 This is a very special aio request: Instead of doing something, it 1120 This is a very special aio request: Instead of doing something, it
496 is a container for other aio requests, which is useful if you want 1121 is a container for other aio requests, which is useful if you want
497 to bundle many requests into a single, composite, request with a 1122 to bundle many requests into a single, composite, request with a
… …
532 requests like sleep and file handle readable/writable, the overhead 1157 requests like sleep and file handle readable/writable, the overhead
533 this creates is immense (it blocks a thread for a long time) so do 1158 this creates is immense (it blocks a thread for a long time) so do
534 not use this function except to put your application under 1159 not use this function except to put your application under
535 artificial I/O pressure. 1160 artificial I/O pressure.
536 1161
1162 IO::AIO::WD - multiple working directories
1163 Your process only has one current working directory, which is used by
1164 all threads. This makes it hard to use relative paths (some other
1165 component could call "chdir" at any time, and it is hard to control when
1166 the path will be used by IO::AIO).
1167
1168 One solution for this is to always use absolute paths. This usually
1169 works, but can be quite slow (the kernel has to walk the whole path on
1170 every access), and can also be a hassle to implement.
1171
1172 Newer POSIX systems have a number of functions (openat, fdopendir,
1173 futimensat and so on) that make it possible to specify working
1174 directories per operation.
1175
1176 For portability, and because the clowns who "designed", or shall I
1177 write, perpetrated this new interface were obviously half-drunk, this
1178 abstraction cannot be perfect, though.
1179
1180 IO::AIO allows you to convert directory paths into a so-called
1181 IO::AIO::WD object. This object stores the canonicalised, absolute
1182 version of the path, and on systems that allow it, also a directory file
1183 descriptor.
1184
1185 Everywhere where a pathname is accepted by IO::AIO (e.g. in "aio_stat"
1186 or "aio_unlink"), one can specify an array reference with an IO::AIO::WD
1187 object and a pathname instead (or the IO::AIO::WD object alone, which
1188 gets interpreted as "[$wd, "."]"). If the pathname is absolute, the
1189 IO::AIO::WD object is ignored, otherwise the pathname is resolved
1190 relative to that IO::AIO::WD object.
1191
1192 For example, to get a wd object for /etc and then stat passwd inside,
1193 you would write:
1194
1195 aio_wd "/etc", sub {
1196 my $etcdir = shift;
1197
1198 # although $etcdir can be undef on error, there is generally no reason
1199 # to check for errors here, as aio_stat will fail with ENOENT
1200 # when $etcdir is undef.
1201
1202 aio_stat [$etcdir, "passwd"], sub {
1203 # yay
1204 };
1205 };
1206
1207 The fact that "aio_wd" is a request and not a normal function shows that
1208 creating an IO::AIO::WD object is itself a potentially blocking
1209 operation, which is why it is done asynchronously.
1210
1211 To stat the directory obtained with "aio_wd" above, one could write
1212 either of the following three request calls:
1213
1214 aio_lstat "/etc" , sub { ... # pathname as normal string
1215 aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
1216 aio_lstat $wd , sub { ... # shorthand for the previous
1217
1218 As with normal pathnames, IO::AIO keeps a copy of the working directory
1219 object and the pathname string, so you could write the following without
1220 causing any issues due to $path getting reused:
1221
1222 my $path = [$wd, undef];
1223
1224 for my $name (qw(abc def ghi)) {
1225 $path->[1] = $name;
1226 aio_stat $path, sub {
1227 # ...
1228 };
1229 }
1230
1231 There are some caveats: when directories get renamed (or deleted), the
1232 pathname string doesn't change, so will point to the new directory (or
1233 nowhere at all), while the directory fd, if available on the system,
1234 will still point to the original directory. Most functions accepting a
1235 pathname will use the directory fd on newer systems, and the string on
1236 older systems. Some functions (such as "aio_realpath") will always rely
1237 on the string form of the pathname.
1238
1239 So this functionality is mainly useful to get some protection against
1240 "chdir", to easily get an absolute path out of a relative path for
1241 future reference, and to speed up doing many operations in the same
1242 directory (e.g. when stat'ing all files in a directory).
1243
1244 The following functions implement this working directory abstraction:
1245
1246 aio_wd $pathname, $callback->($wd)
1247 Asynchonously canonicalise the given pathname and convert it to an
1248 IO::AIO::WD object representing it. If possible and supported on the
1249 system, also open a directory fd to speed up pathname resolution
1250 relative to this working directory.
1251
1252 If something goes wrong, then "undef" is passwd to the callback
1253 instead of a working directory object and $! is set appropriately.
1254 Since passing "undef" as working directory component of a pathname
1255 fails the request with "ENOENT", there is often no need for error
1256 checking in the "aio_wd" callback, as future requests using the
1257 value will fail in the expected way.
1258
1259 IO::AIO::CWD
1260 This is a compile time constant (object) that represents the process
1261 current working directory.
1262
1263 Specifying this object as working directory object for a pathname is
1264 as if the pathname would be specified directly, without a directory
1265 object. For example, these calls are functionally identical:
1266
1267 aio_stat "somefile", sub { ... };
1268 aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
1269
1270 To recover the path associated with an IO::AIO::WD object, you can use
1271 "aio_realpath":
1272
1273 aio_realpath $wd, sub {
1274 warn "path is $_[0]\n";
1275 };
1276
1277 Currently, "aio_statvfs" always, and "aio_rename" and "aio_rmdir"
1278 sometimes, fall back to using an absolue path.
1279
537 IO::AIO::REQ CLASS 1280 IO::AIO::REQ CLASS
538 All non-aggregate "aio_*" functions return an object of this class when 1281 All non-aggregate "aio_*" functions return an object of this class when
539 called in non-void context. 1282 called in non-void context.
540 1283
541 cancel $req 1284 cancel $req
542 Cancels the request, if possible. Has the effect of skipping 1285 Cancels the request, if possible. Has the effect of skipping
543 execution when entering the execute state and skipping calling the 1286 execution when entering the execute state and skipping calling the
544 callback when entering the the result state, but will leave the 1287 callback when entering the the result state, but will leave the
545 request otherwise untouched. That means that requests that currently 1288 request otherwise untouched (with the exception of readdir). That
546 execute will not be stopped and resources held by the request will 1289 means that requests that currently execute will not be stopped and
547 not be freed prematurely. 1290 resources held by the request will not be freed prematurely.
548 1291
549 cb $req $callback->(...) 1292 cb $req $callback->(...)
550 Replace (or simply set) the callback registered to the request. 1293 Replace (or simply set) the callback registered to the request.
551 1294
552 IO::AIO::GRP CLASS 1295 IO::AIO::GRP CLASS
… …
579 }; 1322 };
580 1323
581 This makes it very easy to create composite requests (see the source of 1324 This makes it very easy to create composite requests (see the source of
582 "aio_move" for an application) that work and feel like simple requests. 1325 "aio_move" for an application) that work and feel like simple requests.
583 1326
584 * The IO::AIO::GRP objects will be cleaned up during calls to 1327 * The IO::AIO::GRP objects will be cleaned up during calls to
585 "IO::AIO::poll_cb", just like any other request. 1328 "IO::AIO::poll_cb", just like any other request.
1329
586 * They can be canceled like any other request. Canceling will cancel not 1330 * They can be canceled like any other request. Canceling will cancel
587 only the request itself, but also all requests it contains. 1331 not only the request itself, but also all requests it contains.
1332
588 * They can also can also be added to other IO::AIO::GRP objects. 1333 * They can also can also be added to other IO::AIO::GRP objects.
1334
589 * You must not add requests to a group from within the group callback 1335 * You must not add requests to a group from within the group callback
590 (or any later time). 1336 (or any later time).
591 1337
592 Their lifetime, simplified, looks like this: when they are empty, they 1338 Their lifetime, simplified, looks like this: when they are empty, they
593 will finish very quickly. If they contain only requests that are in the 1339 will finish very quickly. If they contain only requests that are in the
594 "done" state, they will also finish. Otherwise they will continue to 1340 "done" state, they will also finish. Otherwise they will continue to
595 exist. 1341 exist.
596 1342
597 That means after creating a group you have some time to add requests. 1343 That means after creating a group you have some time to add requests
598 And in the callbacks of those requests, you can add further requests to 1344 (precisely before the callback has been invoked, which is only done
599 the group. And only when all those requests have finished will the the 1345 within the "poll_cb"). And in the callbacks of those requests, you can
600 group itself finish. 1346 add further requests to the group. And only when all those requests have
1347 finished will the the group itself finish.
601 1348
602 add $grp ... 1349 add $grp ...
603 $grp->add (...) 1350 $grp->add (...)
604 Add one or more requests to the group. Any type of IO::AIO::REQ can 1351 Add one or more requests to the group. Any type of IO::AIO::REQ can
605 be added, including other groups, as long as you do not create 1352 be added, including other groups, as long as you do not create
… …
610 $grp->cancel_subs 1357 $grp->cancel_subs
611 Cancel all subrequests and clears any feeder, but not the group 1358 Cancel all subrequests and clears any feeder, but not the group
612 request itself. Useful when you queued a lot of events but got a 1359 request itself. Useful when you queued a lot of events but got a
613 result early. 1360 result early.
614 1361
1362 The group request will finish normally (you cannot add requests to
1363 the group).
1364
615 $grp->result (...) 1365 $grp->result (...)
616 Set the result value(s) that will be passed to the group callback 1366 Set the result value(s) that will be passed to the group callback
617 when all subrequests have finished and set thre groups errno to the 1367 when all subrequests have finished and set the groups errno to the
618 current value of errno (just like calling "errno" without an error 1368 current value of errno (just like calling "errno" without an error
619 number). By default, no argument will be passed and errno is zero. 1369 number). By default, no argument will be passed and errno is zero.
620 1370
621 $grp->errno ([$errno]) 1371 $grp->errno ([$errno])
622 Sets the group errno value to $errno, or the current value of errno 1372 Sets the group errno value to $errno, or the current value of errno
… …
633 Sets a feeder/generator on this group: every group can have an 1383 Sets a feeder/generator on this group: every group can have an
634 attached generator that generates requests if idle. The idea behind 1384 attached generator that generates requests if idle. The idea behind
635 this is that, although you could just queue as many requests as you 1385 this is that, although you could just queue as many requests as you
636 want in a group, this might starve other requests for a potentially 1386 want in a group, this might starve other requests for a potentially
637 long time. For example, "aio_scandir" might generate hundreds of 1387 long time. For example, "aio_scandir" might generate hundreds of
638 thousands "aio_stat" requests, delaying any later requests for a 1388 thousands of "aio_stat" requests, delaying any later requests for a
639 long time. 1389 long time.
640 1390
641 To avoid this, and allow incremental generation of requests, you can 1391 To avoid this, and allow incremental generation of requests, you can
642 instead a group and set a feeder on it that generates those 1392 instead a group and set a feeder on it that generates those
643 requests. The feed callback will be called whenever there are few 1393 requests. The feed callback will be called whenever there are few
… …
648 does not impose any limits). 1398 does not impose any limits).
649 1399
650 If the feed does not queue more requests when called, it will be 1400 If the feed does not queue more requests when called, it will be
651 automatically removed from the group. 1401 automatically removed from the group.
652 1402
653 If the feed limit is 0, it will be set to 2 automatically. 1403 If the feed limit is 0 when this method is called, it will be set to
1404 2 automatically.
654 1405
655 Example: 1406 Example:
656 1407
657 # stat all files in @files, but only ever use four aio requests concurrently: 1408 # stat all files in @files, but only ever use four aio requests concurrently:
658 1409
… …
669 Sets the feeder limit for the group: The feeder will be called 1420 Sets the feeder limit for the group: The feeder will be called
670 whenever the group contains less than this many requests. 1421 whenever the group contains less than this many requests.
671 1422
672 Setting the limit to 0 will pause the feeding process. 1423 Setting the limit to 0 will pause the feeding process.
673 1424
1425 The default value for the limit is 0, but note that setting a feeder
1426 automatically bumps it up to 2.
1427
674 SUPPORT FUNCTIONS 1428 SUPPORT FUNCTIONS
675 EVENT PROCESSING AND EVENT LOOP INTEGRATION 1429 EVENT PROCESSING AND EVENT LOOP INTEGRATION
676 $fileno = IO::AIO::poll_fileno 1430 $fileno = IO::AIO::poll_fileno
677 Return the *request result pipe file descriptor*. This filehandle 1431 Return the *request result pipe file descriptor*. This filehandle
678 must be polled for reading by some mechanism outside this module 1432 must be polled for reading by some mechanism outside this module
679 (e.g. Event or select, see below or the SYNOPSIS). If the pipe 1433 (e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
680 becomes readable you have to call "poll_cb" to check the results. 1434 pipe becomes readable you have to call "poll_cb" to check the
1435 results.
681 1436
682 See "poll_cb" for an example. 1437 See "poll_cb" for an example.
683 1438
684 IO::AIO::poll_cb 1439 IO::AIO::poll_cb
685 Process some outstanding events on the result pipe. You have to call 1440 Process some requests that have reached the result phase (i.e. they
686 this regularly. Returns the number of events processed. Returns 1441 have been executed but the results are not yet reported). You have
1442 to call this "regularly" to finish outstanding requests.
1443
1444 Returns 0 if all events could be processed (or there were no events
1445 to process), or -1 if it returned earlier for whatever reason.
687 immediately when no events are outstanding. The amount of events 1446 Returns immediately when no events are outstanding. The amount of
688 processed depends on the settings of "IO::AIO::max_poll_req" and 1447 events processed depends on the settings of "IO::AIO::max_poll_req",
689 "IO::AIO::max_poll_time". 1448 "IO::AIO::max_poll_time" and "IO::AIO::max_outstanding".
690 1449
691 If not all requests were processed for whatever reason, the 1450 If not all requests were processed for whatever reason, the poll
692 filehandle will still be ready when "poll_cb" returns. 1451 file descriptor will still be ready when "poll_cb" returns, so
1452 normally you don't have to do anything special to have it called
1453 later.
1454
1455 Apart from calling "IO::AIO::poll_cb" when the event filehandle
1456 becomes ready, it can be beneficial to call this function from loops
1457 which submit a lot of requests, to make sure the results get
1458 processed when they become available and not just when the loop is
1459 finished and the event loop takes over again. This function returns
1460 very fast when there are no outstanding requests.
693 1461
694 Example: Install an Event watcher that automatically calls 1462 Example: Install an Event watcher that automatically calls
695 IO::AIO::poll_cb with high priority: 1463 IO::AIO::poll_cb with high priority (more examples can be found in
1464 the SYNOPSIS section, at the top of this document):
696 1465
697 Event->io (fd => IO::AIO::poll_fileno, 1466 Event->io (fd => IO::AIO::poll_fileno,
698 poll => 'r', async => 1, 1467 poll => 'r', async => 1,
699 cb => \&IO::AIO::poll_cb); 1468 cb => \&IO::AIO::poll_cb);
1469
1470 IO::AIO::poll_wait
1471 Wait until either at least one request is in the result phase or no
1472 requests are outstanding anymore.
1473
1474 This is useful if you want to synchronously wait for some requests
1475 to become ready, without actually handling them.
1476
1477 See "nreqs" for an example.
1478
1479 IO::AIO::poll
1480 Waits until some requests have been handled.
1481
1482 Returns the number of requests processed, but is otherwise strictly
1483 equivalent to:
1484
1485 IO::AIO::poll_wait, IO::AIO::poll_cb
1486
1487 IO::AIO::flush
1488 Wait till all outstanding AIO requests have been handled.
1489
1490 Strictly equivalent to:
1491
1492 IO::AIO::poll_wait, IO::AIO::poll_cb
1493 while IO::AIO::nreqs;
1494
1495 This function can be useful at program aborts, to make sure
1496 outstanding I/O has been done ("IO::AIO" uses an "END" block which
1497 already calls this function on normal exits), or when you are merely
1498 using "IO::AIO" for its more advanced functions, rather than for
1499 async I/O, e.g.:
1500
1501 my ($dirs, $nondirs);
1502 IO::AIO::aio_scandir "/tmp", 0, sub { ($dirs, $nondirs) = @_ };
1503 IO::AIO::flush;
1504 # $dirs, $nondirs are now set
700 1505
701 IO::AIO::max_poll_reqs $nreqs 1506 IO::AIO::max_poll_reqs $nreqs
702 IO::AIO::max_poll_time $seconds 1507 IO::AIO::max_poll_time $seconds
703 These set the maximum number of requests (default 0, meaning 1508 These set the maximum number of requests (default 0, meaning
704 infinity) that are being processed by "IO::AIO::poll_cb" in one 1509 infinity) that are being processed by "IO::AIO::poll_cb" in one
… …
728 # use a low priority so other tasks have priority 1533 # use a low priority so other tasks have priority
729 Event->io (fd => IO::AIO::poll_fileno, 1534 Event->io (fd => IO::AIO::poll_fileno,
730 poll => 'r', nice => 1, 1535 poll => 'r', nice => 1,
731 cb => &IO::AIO::poll_cb); 1536 cb => &IO::AIO::poll_cb);
732 1537
733 IO::AIO::poll_wait
734 If there are any outstanding requests and none of them in the result
735 phase, wait till the result filehandle becomes ready for reading
736 (simply does a "select" on the filehandle. This is useful if you
737 want to synchronously wait for some requests to finish).
738
739 See "nreqs" for an example.
740
741 IO::AIO::poll
742 Waits until some requests have been handled.
743
744 Returns the number of requests processed, but is otherwise strictly
745 equivalent to:
746
747 IO::AIO::poll_wait, IO::AIO::poll_cb
748
749 IO::AIO::flush
750 Wait till all outstanding AIO requests have been handled.
751
752 Strictly equivalent to:
753
754 IO::AIO::poll_wait, IO::AIO::poll_cb
755 while IO::AIO::nreqs;
756
757 CONTROLLING THE NUMBER OF THREADS 1538 CONTROLLING THE NUMBER OF THREADS
758 IO::AIO::min_parallel $nthreads 1539 IO::AIO::min_parallel $nthreads
759 Set the minimum number of AIO threads to $nthreads. The current 1540 Set the minimum number of AIO threads to $nthreads. The current
760 default is 8, which means eight asynchronous operations can execute 1541 default is 8, which means eight asynchronous operations can execute
761 concurrently at any one time (the number of outstanding requests, 1542 concurrently at any one time (the number of outstanding requests,
… …
790 1571
791 Under normal circumstances you don't need to call this function. 1572 Under normal circumstances you don't need to call this function.
792 1573
793 IO::AIO::max_idle $nthreads 1574 IO::AIO::max_idle $nthreads
794 Limit the number of threads (default: 4) that are allowed to idle 1575 Limit the number of threads (default: 4) that are allowed to idle
795 (i.e., threads that did not get a request to process within 10 1576 (i.e., threads that did not get a request to process within the idle
796 seconds). That means if a thread becomes idle while $nthreads other 1577 timeout (default: 10 seconds). That means if a thread becomes idle
797 threads are also idle, it will free its resources and exit. 1578 while $nthreads other threads are also idle, it will free its
1579 resources and exit.
798 1580
799 This is useful when you allow a large number of threads (e.g. 100 or 1581 This is useful when you allow a large number of threads (e.g. 100 or
800 1000) to allow for extremely high load situations, but want to free 1582 1000) to allow for extremely high load situations, but want to free
801 resources under normal circumstances (1000 threads can easily 1583 resources under normal circumstances (1000 threads can easily
802 consume 30MB of RAM). 1584 consume 30MB of RAM).
803 1585
804 The default is probably ok in most situations, especially if thread 1586 The default is probably ok in most situations, especially if thread
805 creation is fast. If thread creation is very slow on your system you 1587 creation is fast. If thread creation is very slow on your system you
806 might want to use larger values. 1588 might want to use larger values.
807 1589
1590 IO::AIO::idle_timeout $seconds
1591 Sets the minimum idle timeout (default 10) after which worker
1592 threads are allowed to exit. SEe "IO::AIO::max_idle".
1593
808 $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1594 IO::AIO::max_outstanding $maxreqs
809 This is a very bad function to use in interactive programs because
810 it blocks, and a bad way to reduce concurrency because it is
811 inexact: Better use an "aio_group" together with a feed callback.
812
813 Sets the maximum number of outstanding requests to $nreqs. If you to 1595 Sets the maximum number of outstanding requests to $nreqs. If you do
814 queue up more than this number of requests, the next call to the 1596 queue up more than this number of requests, the next call to
815 "poll_cb" (and "poll_some" and other functions calling "poll_cb") 1597 "IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
816 function will block until the limit is no longer exceeded. 1598 "IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
1599 no longer exceeded.
817 1600
818 The default value is very large, so there is no practical limit on 1601 In other words, this setting does not enforce a queue limit, but can
1602 be used to make poll functions block if the limit is exceeded.
1603
1604 This is a bad function to use in interactive programs because it
1605 blocks, and a bad way to reduce concurrency because it is inexact.
1606 If you need to issue many requests without being able to call a poll
1607 function on demand, it is better to use an "aio_group" together with
1608 a feed callback.
1609
1610 Its main use is in scripts without an event loop - when you want to
1611 stat a lot of files, you can write something like this:
1612
1613 IO::AIO::max_outstanding 32;
1614
1615 for my $path (...) {
1616 aio_stat $path , ...;
1617 IO::AIO::poll_cb;
1618 }
1619
1620 IO::AIO::flush;
1621
1622 The call to "poll_cb" inside the loop will normally return
1623 instantly, allowing the loop to progress, but as soon as more than
1624 32 requests are in-flight, it will block until some requests have
1625 been handled. This keeps the loop from pushing a large number of
1626 "aio_stat" requests onto the queue (which, with many paths to stat,
1627 can use up a lot of memory).
1628
1629 The default value for "max_outstanding" is very large, so there is
819 the number of outstanding requests. 1630 no practical limit on the number of outstanding requests.
820
821 You can still queue as many requests as you want. Therefore,
822 "max_oustsanding" is mainly useful in simple scripts (with low
823 values) or as a stop gap to shield against fatal memory overflow
824 (with large values).
825 1631
826 STATISTICAL INFORMATION 1632 STATISTICAL INFORMATION
827 IO::AIO::nreqs 1633 IO::AIO::nreqs
828 Returns the number of requests currently in the ready, execute or 1634 Returns the number of requests currently in the ready, execute or
829 pending states (i.e. for which their callback has not been invoked 1635 pending states (i.e. for which their callback has not been invoked
… …
840 1646
841 IO::AIO::npending 1647 IO::AIO::npending
842 Returns the number of requests currently in the pending state 1648 Returns the number of requests currently in the pending state
843 (executed, but not yet processed by poll_cb). 1649 (executed, but not yet processed by poll_cb).
844 1650
1651 SUBSECOND STAT TIME ACCESS
1652 Both "aio_stat"/"aio_lstat" and perl's "stat"/"lstat" functions can
1653 generally find access/modification and change times with subsecond time
1654 accuracy of the system supports it, but perl's built-in functions only
1655 return the integer part.
1656
1657 The following functions return the timestamps of the most recent stat
1658 with subsecond precision on most systems and work both after
1659 "aio_stat"/"aio_lstat" and perl's "stat"/"lstat" calls. Their return
1660 value is only meaningful after a successful "stat"/"lstat" call, or
1661 during/after a successful "aio_stat"/"aio_lstat" callback.
1662
1663 This is similar to the Time::HiRes "stat" functions, but can return full
1664 resolution without rounding and work with standard perl "stat",
1665 alleviating the need to call the special "Time::HiRes" functions, which
1666 do not act like their perl counterparts.
1667
1668 On operating systems or file systems where subsecond time resolution is
1669 not supported or could not be detected, a fractional part of 0 is
1670 returned, so it is always safe to call these functions.
1671
1672 $seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime,
1673 IO::AIO::st_btime
1674 Return the access, modication, change or birth time, respectively,
1675 including fractional part. Due to the limited precision of floating
1676 point, the accuracy on most platforms is only a bit better than
1677 milliseconds for times around now - see the *nsec* function family,
1678 below, for full accuracy.
1679
1680 File birth time is only available when the OS and perl support it
1681 (on FreeBSD and NetBSD at the time of this writing, although support
1682 is adaptive, so if your OS/perl gains support, IO::AIO can take
1683 advantage of it). On systems where it isn't available, 0 is
1684 currently returned, but this might change to "undef" in a future
1685 version.
1686
1687 ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
1688 Returns access, modification, change and birth time all in one go,
1689 and maybe more times in the future version.
1690
1691 $nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec,
1692 IO::AIO::st_ctimensec, IO::AIO::st_btimensec
1693 Return the fractional access, modifcation, change or birth time, in
1694 nanoseconds, as an integer in the range 0 to 999999999.
1695
1696 Note that no accessors are provided for access, modification and
1697 change times - you need to get those from "stat _" if required ("int
1698 IO::AIO::st_atime" and so on will *not* generally give you the
1699 correct value).
1700
1701 $seconds = IO::AIO::st_btimesec
1702 The (integral) seconds part of the file birth time, if available.
1703
1704 ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
1705 Like the functions above, but returns all four times in one go (and
1706 maybe more in future versions).
1707
1708 $counter = IO::AIO::st_gen
1709 Returns the generation counter (in practice this is just a random
1710 number) of the file. This is only available on platforms which have
1711 this member in their "struct stat" (most BSDs at the time of this
1712 writing) and generally only to the root usert. If unsupported, 0 is
1713 returned, but this might change to "undef" in a future version.
1714
1715 Example: print the high resolution modification time of /etc, using
1716 "stat", and "IO::AIO::aio_stat".
1717
1718 if (stat "/etc") {
1719 printf "stat(/etc) mtime: %f\n", IO::AIO::st_mtime;
1720 }
1721
1722 IO::AIO::aio_stat "/etc", sub {
1723 $_[0]
1724 and return;
1725
1726 printf "aio_stat(/etc) mtime: %d.%09d\n", (stat _)[9], IO::AIO::st_mtimensec;
1727 };
1728
1729 IO::AIO::flush;
1730
1731 Output of the awbove on my system, showing reduced and full accuracy:
1732
1733 stat(/etc) mtime: 1534043702.020808
1734 aio_stat(/etc) mtime: 1534043702.020807792
1735
1736 MISCELLANEOUS FUNCTIONS
1737 IO::AIO implements some functions that are useful when you want to use
1738 some "Advanced I/O" function not available to in Perl, without going the
1739 "Asynchronous I/O" route. Many of these have an asynchronous "aio_*"
1740 counterpart.
1741
1742 $retval = IO::AIO::fexecve $fh, $argv, $envp
1743 A more-or-less direct equivalent to the POSIX "fexecve" functions,
1744 which allows you to specify the program to be executed via a file
1745 descriptor (or handle). Returns -1 and sets errno to "ENOSYS" if not
1746 available.
1747
1748 $numfd = IO::AIO::get_fdlimit
1749 Tries to find the current file descriptor limit and returns it, or
1750 "undef" and sets $! in case of an error. The limit is one larger
1751 than the highest valid file descriptor number.
1752
1753 IO::AIO::min_fdlimit [$numfd]
1754 Try to increase the current file descriptor limit(s) to at least
1755 $numfd by changing the soft or hard file descriptor resource limit.
1756 If $numfd is missing, it will try to set a very high limit, although
1757 this is not recommended when you know the actual minimum that you
1758 require.
1759
1760 If the limit cannot be raised enough, the function makes a
1761 best-effort attempt to increase the limit as much as possible, using
1762 various tricks, while still failing. You can query the resulting
1763 limit using "IO::AIO::get_fdlimit".
1764
1765 If an error occurs, returns "undef" and sets $!, otherwise returns
1766 true.
1767
1768 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1769 Calls the "eio_sendfile_sync" function, which is like
1770 "aio_sendfile", but is blocking (this makes most sense if you know
1771 the input data is likely cached already and the output filehandle is
1772 set to non-blocking operations).
1773
1774 Returns the number of bytes copied, or -1 on error.
1775
1776 IO::AIO::fadvise $fh, $offset, $len, $advice
1777 Simply calls the "posix_fadvise" function (see its manpage for
1778 details). The following advice constants are available:
1779 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1780 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1781 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1782
1783 On systems that do not implement "posix_fadvise", this function
1784 returns ENOSYS, otherwise the return value of "posix_fadvise".
1785
1786 IO::AIO::madvise $scalar, $offset, $len, $advice
1787 Simply calls the "posix_madvise" function (see its manpage for
1788 details). The following advice constants are available:
1789 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1790 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1791 "IO::AIO::MADV_DONTNEED".
1792
1793 If $offset is negative, counts from the end. If $length is negative,
1794 the remaining length of the $scalar is used. If possible, $length
1795 will be reduced to fit into the $scalar.
1796
1797 On systems that do not implement "posix_madvise", this function
1798 returns ENOSYS, otherwise the return value of "posix_madvise".
1799
1800 IO::AIO::mprotect $scalar, $offset, $len, $protect
1801 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1802 $scalar (see its manpage for details). The following protect
1803 constants are available: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1804 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1805
1806 If $offset is negative, counts from the end. If $length is negative,
1807 the remaining length of the $scalar is used. If possible, $length
1808 will be reduced to fit into the $scalar.
1809
1810 On systems that do not implement "mprotect", this function returns
1811 ENOSYS, otherwise the return value of "mprotect".
1812
1813 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1814 Memory-maps a file (or anonymous memory range) and attaches it to
1815 the given $scalar, which will act like a string scalar. Returns true
1816 on success, and false otherwise.
1817
1818 The scalar must exist, but its contents do not matter - this means
1819 you cannot use a nonexistant array or hash element. When in doubt,
1820 "undef" the scalar first.
1821
1822 The only operations allowed on the mmapped scalar are
1823 "substr"/"vec", which don't change the string length, and most
1824 read-only operations such as copying it or searching it with regexes
1825 and so on.
1826
1827 Anything else is unsafe and will, at best, result in memory leaks.
1828
1829 The memory map associated with the $scalar is automatically removed
1830 when the $scalar is undef'd or destroyed, or when the
1831 "IO::AIO::mmap" or "IO::AIO::munmap" functions are called on it.
1832
1833 This calls the "mmap"(2) function internally. See your system's
1834 manual page for details on the $length, $prot and $flags parameters.
1835
1836 The $length must be larger than zero and smaller than the actual
1837 filesize.
1838
1839 $prot is a combination of "IO::AIO::PROT_NONE",
1840 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1841 "IO::AIO::PROT_WRITE",
1842
1843 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1844 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1845 not available, the are 0): "IO::AIO::MAP_ANONYMOUS" (which is set to
1846 "MAP_ANON" if your system only provides this constant),
1847 "IO::AIO::MAP_LOCKED", "IO::AIO::MAP_NORESERVE",
1848 "IO::AIO::MAP_POPULATE", "IO::AIO::MAP_NONBLOCK",
1849 "IO::AIO::MAP_FIXED", "IO::AIO::MAP_GROWSDOWN",
1850 "IO::AIO::MAP_32BIT", "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_STACK",
1851 "IO::AIO::MAP_FIXED_NOREPLACE", "IO::AIO::MAP_SHARED_VALIDATE",
1852 "IO::AIO::MAP_SYNC" or "IO::AIO::MAP_UNINITIALIZED".
1853
1854 If $fh is "undef", then a file descriptor of -1 is passed.
1855
1856 $offset is the offset from the start of the file - it generally must
1857 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
1858
1859 Example:
1860
1861 use Digest::MD5;
1862 use IO::AIO;
1863
1864 open my $fh, "<verybigfile"
1865 or die "$!";
1866
1867 IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
1868 or die "verybigfile: $!";
1869
1870 my $fast_md5 = md5 $data;
1871
1872 IO::AIO::munmap $scalar
1873 Removes a previous mmap and undefines the $scalar.
1874
1875 IO::AIO::mremap $scalar, $new_length, $flags = MREMAP_MAYMOVE[,
1876 $new_address = 0]
1877 Calls the Linux-specific mremap(2) system call. The $scalar must
1878 have been mapped by "IO::AIO::mmap", and $flags must currently
1879 either be 0 or "IO::AIO::MREMAP_MAYMOVE".
1880
1881 Returns true if successful, and false otherwise. If the underlying
1882 mmapped region has changed address, then the true value has the
1883 numerical value 1, otherwise it has the numerical value 0:
1884
1885 my $success = IO::AIO::mremap $mmapped, 8192, IO::AIO::MREMAP_MAYMOVE
1886 or die "mremap: $!";
1887
1888 if ($success*1) {
1889 warn "scalar has chanegd address in memory\n";
1890 }
1891
1892 "IO::AIO::MREMAP_FIXED" and the $new_address argument are currently
1893 implemented, but not supported and might go away in a future
1894 version.
1895
1896 On systems where this call is not supported or is not emulated, this
1897 call returns falls and sets $! to "ENOSYS".
1898
1899 IO::AIO::mlockall $flags
1900 Calls the "eio_mlockall_sync" function, which is like
1901 "aio_mlockall", but is blocking.
1902
1903 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1904 Calls the "munlock" function, undoing the effects of a previous
1905 "aio_mlock" call (see its description for details).
1906
1907 IO::AIO::munlockall
1908 Calls the "munlockall" function.
1909
1910 On systems that do not implement "munlockall", this function returns
1911 ENOSYS, otherwise the return value of "munlockall".
1912
1913 $fh = IO::AIO::accept4 $r_fh, $sockaddr, $sockaddr_maxlen, $flags
1914 Uses the GNU/Linux accept4(2) syscall, if available, to accept a
1915 socket and return the new file handle on success, or sets $! and
1916 returns "undef" on error.
1917
1918 The remote name of the new socket will be stored in $sockaddr, which
1919 will be extended to allow for at least $sockaddr_maxlen octets. If
1920 the socket name does not fit into $sockaddr_maxlen octets, this is
1921 signaled by returning a longer string in $sockaddr, which might or
1922 might not be truncated.
1923
1924 To accept name-less sockets, use "undef" for $sockaddr and 0 for
1925 $sockaddr_maxlen.
1926
1927 The main reasons to use this syscall rather than portable accept(2)
1928 are that you can specify "SOCK_NONBLOCK" and/or "SOCK_CLOEXEC" flags
1929 and you can accept name-less sockets by specifying 0 for
1930 $sockaddr_maxlen, which is sadly not possible with perl's interface
1931 to "accept".
1932
1933 IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
1934 Calls the GNU/Linux splice(2) syscall, if available. If $r_off or
1935 $w_off are "undef", then "NULL" is passed for these, otherwise they
1936 should be the file offset.
1937
1938 $r_fh and $w_fh should not refer to the same file, as splice might
1939 silently corrupt the data in this case.
1940
1941 The following symbol flag values are available:
1942 "IO::AIO::SPLICE_F_MOVE", "IO::AIO::SPLICE_F_NONBLOCK",
1943 "IO::AIO::SPLICE_F_MORE" and "IO::AIO::SPLICE_F_GIFT".
1944
1945 See the splice(2) manpage for details.
1946
1947 IO::AIO::tee $r_fh, $w_fh, $length, $flags
1948 Calls the GNU/Linux tee(2) syscall, see its manpage and the
1949 description for "IO::AIO::splice" above for details.
1950
1951 $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
1952 Attempts to query or change the pipe buffer size. Obviously works
1953 only on pipes, and currently works only on GNU/Linux systems, and
1954 fails with -1/"ENOSYS" everywhere else. If anybody knows how to
1955 influence pipe buffer size on other systems, drop me a note.
1956
1957 ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
1958 This is a direct interface to the Linux pipe2(2) system call. If
1959 $flags is missing or 0, then this should be the same as a call to
1960 perl's built-in "pipe" function and create a new pipe, and works on
1961 systems that lack the pipe2 syscall. On win32, this case invokes
1962 "_pipe (..., 4096, O_BINARY)".
1963
1964 If $flags is non-zero, it tries to invoke the pipe2 system call with
1965 the given flags (Linux 2.6.27, glibc 2.9).
1966
1967 On success, the read and write file handles are returned.
1968
1969 On error, nothing will be returned. If the pipe2 syscall is missing
1970 and $flags is non-zero, fails with "ENOSYS".
1971
1972 Please refer to pipe2(2) for more info on the $flags, but at the
1973 time of this writing, "IO::AIO::O_CLOEXEC", "IO::AIO::O_NONBLOCK"
1974 and "IO::AIO::O_DIRECT" (Linux 3.4, for packet-based pipes) were
1975 supported.
1976
1977 Example: create a pipe race-free w.r.t. threads and fork:
1978
1979 my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
1980 or die "pipe2: $!\n";
1981
1982 $fh = IO::AIO::memfd_create $pathname[, $flags]
1983 This is a direct interface to the Linux memfd_create(2) system call.
1984 The (unhelpful) default for $flags is 0, but your default should be
1985 "IO::AIO::MFD_CLOEXEC".
1986
1987 On success, the new memfd filehandle is returned, otherwise returns
1988 "undef". If the memfd_create syscall is missing, fails with
1989 "ENOSYS".
1990
1991 Please refer to memfd_create(2) for more info on this call.
1992
1993 The following $flags values are available: "IO::AIO::MFD_CLOEXEC",
1994 "IO::AIO::MFD_ALLOW_SEALING", "IO::AIO::MFD_HUGETLB",
1995 "IO::AIO::MFD_HUGETLB_2MB" and "IO::AIO::MFD_HUGETLB_1GB".
1996
1997 Example: create a new memfd.
1998
1999 my $fh = IO::AIO::memfd_create "somenameforprocfd", IO::AIO::MFD_CLOEXEC
2000 or die "memfd_create: $!\n";
2001
2002 $fh = IO::AIO::pidfd_open $pid[, $flags]
2003 This is an interface to the Linux pidfd_open(2) system call. The
2004 default for $flags is 0.
2005
2006 On success, a new pidfd filehandle is returned (that is already set
2007 to close-on-exec), otherwise returns "undef". If the syscall is
2008 missing, fails with "ENOSYS".
2009
2010 Example: open pid 6341 as pidfd.
2011
2012 my $fh = IO::AIO::pidfd_open 6341
2013 or die "pidfd_open: $!\n";
2014
2015 $status = IO::AIO::pidfd_send_signal $pidfh, $signal[, $siginfo[,
2016 $flags]]
2017 This is an interface to the Linux pidfd_send_signal system call. The
2018 default for $siginfo is "undef" and the default for $flags is 0.
2019
2020 Returns the system call status. If the syscall is missing, fails
2021 with "ENOSYS".
2022
2023 When specified, $siginfo must be a reference to a hash with one or
2024 more of the following members:
2025
2026 code - the "si_code" member
2027 pid - the "si_pid" member
2028 uid - the "si_uid" member
2029 value_int - the "si_value.sival_int" member
2030 value_ptr - the "si_value.sival_ptr" member, specified as an integer
2031
2032 Example: send a SIGKILL to the specified process.
2033
2034 my $status = IO::AIO::pidfd_send_signal $pidfh, 9, undef
2035 and die "pidfd_send_signal: $!\n";
2036
2037 Example: send a SIGKILL to the specified process with extra data.
2038
2039 my $status = IO::AIO::pidfd_send_signal $pidfh, 9, { code => -1, value_int => 7 }
2040 and die "pidfd_send_signal: $!\n";
2041
2042 $fh = IO::AIO::pidfd_getfd $pidfh, $targetfd[, $flags]
2043 This is an interface to the Linux pidfd_getfd system call. The
2044 default for $flags is 0.
2045
2046 On success, returns a dup'ed copy of the target file descriptor
2047 (specified as an integer) returned (that is already set to
2048 close-on-exec), otherwise returns "undef". If the syscall is
2049 missing, fails with "ENOSYS".
2050
2051 Example: get a copy of standard error of another process and print
2052 soemthing to it.
2053
2054 my $errfh = IO::AIO::pidfd_getfd $pidfh, 2
2055 or die "pidfd_getfd: $!\n";
2056 print $errfh "stderr\n";
2057
2058 $fh = IO::AIO::eventfd [$initval, [$flags]]
2059 This is a direct interface to the Linux eventfd(2) system call. The
2060 (unhelpful) defaults for $initval and $flags are 0 for both.
2061
2062 On success, the new eventfd filehandle is returned, otherwise
2063 returns "undef". If the eventfd syscall is missing, fails with
2064 "ENOSYS".
2065
2066 Please refer to eventfd(2) for more info on this call.
2067
2068 The following symbol flag values are available:
2069 "IO::AIO::EFD_CLOEXEC", "IO::AIO::EFD_NONBLOCK" and
2070 "IO::AIO::EFD_SEMAPHORE" (Linux 2.6.30).
2071
2072 Example: create a new eventfd filehandle:
2073
2074 $fh = IO::AIO::eventfd 0, IO::AIO::EFD_CLOEXEC
2075 or die "eventfd: $!\n";
2076
2077 $fh = IO::AIO::timerfd_create $clockid[, $flags]
2078 This is a direct interface to the Linux timerfd_create(2) system
2079 call. The (unhelpful) default for $flags is 0, but your default
2080 should be "IO::AIO::TFD_CLOEXEC".
2081
2082 On success, the new timerfd filehandle is returned, otherwise
2083 returns "undef". If the timerfd_create syscall is missing, fails
2084 with "ENOSYS".
2085
2086 Please refer to timerfd_create(2) for more info on this call.
2087
2088 The following $clockid values are available:
2089 "IO::AIO::CLOCK_REALTIME", "IO::AIO::CLOCK_MONOTONIC"
2090 "IO::AIO::CLOCK_CLOCK_BOOTTIME" (Linux 3.15)
2091 "IO::AIO::CLOCK_CLOCK_REALTIME_ALARM" (Linux 3.11) and
2092 "IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM" (Linux 3.11).
2093
2094 The following $flags values are available (Linux 2.6.27):
2095 "IO::AIO::TFD_NONBLOCK" and "IO::AIO::TFD_CLOEXEC".
2096
2097 Example: create a new timerfd and set it to one-second repeated
2098 alarms, then wait for two alarms:
2099
2100 my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
2101 or die "timerfd_create: $!\n";
2102
2103 defined IO::AIO::timerfd_settime $fh, 0, 1, 1
2104 or die "timerfd_settime: $!\n";
2105
2106 for (1..2) {
2107 8 == sysread $fh, my $buf, 8
2108 or die "timerfd read failure\n";
2109
2110 printf "number of expirations (likely 1): %d\n",
2111 unpack "Q", $buf;
2112 }
2113
2114 ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags,
2115 $new_interval, $nbw_value
2116 This is a direct interface to the Linux timerfd_settime(2) system
2117 call. Please refer to its manpage for more info on this call.
2118
2119 The new itimerspec is specified using two (possibly fractional)
2120 second values, $new_interval and $new_value).
2121
2122 On success, the current interval and value are returned (as per
2123 "timerfd_gettime"). On failure, the empty list is returned.
2124
2125 The following $flags values are available:
2126 "IO::AIO::TFD_TIMER_ABSTIME" and "IO::AIO::TFD_TIMER_CANCEL_ON_SET".
2127
2128 See "IO::AIO::timerfd_create" for a full example.
2129
2130 ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
2131 This is a direct interface to the Linux timerfd_gettime(2) system
2132 call. Please refer to its manpage for more info on this call.
2133
2134 On success, returns the current values of interval and value for the
2135 given timerfd (as potentially fractional second values). On failure,
2136 the empty list is returned.
2137
2138EVENT LOOP INTEGRATION
2139 It is recommended to use AnyEvent::AIO to integrate IO::AIO
2140 automatically into many event loops:
2141
2142 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
2143 use AnyEvent::AIO;
2144
2145 You can also integrate IO::AIO manually into many event loops, here are
2146 some examples of how to do this:
2147
2148 # EV integration
2149 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
2150
2151 # Event integration
2152 Event->io (fd => IO::AIO::poll_fileno,
2153 poll => 'r',
2154 cb => \&IO::AIO::poll_cb);
2155
2156 # Glib/Gtk2 integration
2157 add_watch Glib::IO IO::AIO::poll_fileno,
2158 in => sub { IO::AIO::poll_cb; 1 };
2159
2160 # Tk integration
2161 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
2162 readable => \&IO::AIO::poll_cb);
2163
2164 # Danga::Socket integration
2165 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
2166 \&IO::AIO::poll_cb);
2167
845 FORK BEHAVIOUR 2168 FORK BEHAVIOUR
846 This module should do "the right thing" when the process using it forks: 2169 Usage of pthreads in a program changes the semantics of fork
2170 considerably. Specifically, only async-safe functions can be called
2171 after fork. Perl doesn't know about this, so in general, you cannot call
2172 fork with defined behaviour in perl if pthreads are involved. IO::AIO
2173 uses pthreads, so this applies, but many other extensions and (for
2174 inexplicable reasons) perl itself often is linked against pthreads, so
2175 this limitation applies to quite a lot of perls.
847 2176
848 Before the fork, IO::AIO enters a quiescent state where no requests can 2177 This module no longer tries to fight your OS, or POSIX. That means
849 be added in other threads and no results will be processed. After the 2178 IO::AIO only works in the process that loaded it. Forking is fully
850 fork the parent simply leaves the quiescent state and continues 2179 supported, but using IO::AIO in the child is not.
851 request/result processing, while the child frees the request/result
852 queue (so that the requests started before the fork will only be handled
853 in the parent). Threads will be started on demand until the limit set in
854 the parent process has been reached again.
855 2180
856 In short: the parent will, after a short pause, continue as if fork had 2181 You might get around by not *using* IO::AIO before (or after) forking.
857 not been called, while the child will act as if IO::AIO has not been 2182 You could also try to call the IO::AIO::reinit function in the child:
858 used yet. 2183
2184 IO::AIO::reinit
2185 Abandons all current requests and I/O threads and simply
2186 reinitialises all data structures. This is not an operation
2187 supported by any standards, but happens to work on GNU/Linux and
2188 some newer BSD systems.
2189
2190 The only reasonable use for this function is to call it after
2191 forking, if "IO::AIO" was used in the parent. Calling it while
2192 IO::AIO is active in the process will result in undefined behaviour.
2193 Calling it at any time will also result in any undefined (by POSIX)
2194 behaviour.
2195
2196 LINUX-SPECIFIC CALLS
2197 When a call is documented as "linux-specific" then this means it
2198 originated on GNU/Linux. "IO::AIO" will usually try to autodetect the
2199 availability and compatibility of such calls regardless of the platform
2200 it is compiled on, so platforms such as FreeBSD which often implement
2201 these calls will work. When in doubt, call them and see if they fail wth
2202 "ENOSYS".
859 2203
860 MEMORY USAGE 2204 MEMORY USAGE
861 Per-request usage: 2205 Per-request usage:
862 2206
863 Each aio request uses - depending on your architecture - around 100-200 2207 Each aio request uses - depending on your architecture - around 100-200
864 bytes of memory. In addition, stat requests need a stat buffer (possibly 2208 bytes of memory. In addition, stat requests need a stat buffer (possibly
865 a few hundred bytes), readdir requires a result buffer and so on. Perl 2209 a few hundred bytes), readdir requires a result buffer and so on. Perl
866 scalars and other data passed into aio requests will also be locked and 2210 scalars and other data passed into aio requests will also be locked and
867 will consume memory till the request has entered the done state. 2211 will consume memory till the request has entered the done state.
868 2212
869 This is now awfully much, so queuing lots of requests is not usually a 2213 This is not awfully much, so queuing lots of requests is not usually a
870 problem. 2214 problem.
871 2215
872 Per-thread usage: 2216 Per-thread usage:
873 2217
874 In the execution phase, some aio requests require more memory for 2218 In the execution phase, some aio requests require more memory for
875 temporary buffers, and each thread requires a stack and other data 2219 temporary buffers, and each thread requires a stack and other data
876 structures (usually around 16k-128k, depending on the OS). 2220 structures (usually around 16k-128k, depending on the OS).
877 2221
878KNOWN BUGS 2222KNOWN BUGS
879 Known bugs will be fixed in the next release. 2223 Known bugs will be fixed in the next release :)
2224
2225KNOWN ISSUES
2226 Calls that try to "import" foreign memory areas (such as "IO::AIO::mmap"
2227 or "IO::AIO::aio_slurp") do not work with generic lvalues, such as
2228 non-created hash slots or other scalars I didn't think of. It's best to
2229 avoid such and either use scalar variables or making sure that the
2230 scalar exists (e.g. by storing "undef") and isn't "funny" (e.g. tied).
2231
2232 I am not sure anything can be done about this, so this is considered a
2233 known issue, rather than a bug.
880 2234
881SEE ALSO 2235SEE ALSO
882 Coro::AIO. 2236 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
2237 more natural syntax and IO::FDPass for file descriptor passing.
883 2238
884AUTHOR 2239AUTHOR
885 Marc Lehmann <schmorp@schmorp.de> 2240 Marc Lehmann <schmorp@schmorp.de>
886 http://home.schmorp.de/ 2241 http://home.schmorp.de/
887 2242

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