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Revision 1.55 by root, Sat Jan 25 00:15:52 2014 UTC

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2 IO::AIO - Asynchronous Input/Output 2 IO::AIO - Asynchronous 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
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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
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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
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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
81 Although the module will work with in the presence of other (Perl-) 60 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 61 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 62 yourself, always call "poll_cb" from within the same thread, or never
84 never call "poll_cb" (or other "aio_" functions) recursively. 63 call "poll_cb" (or other "aio_" functions) recursively.
85 64
86 EXAMPLE 65 EXAMPLE
87 This is a simple example that uses the Event module and loads 66 This is a simple example that uses the EV module and loads /etc/passwd
88 /etc/passwd asynchronously: 67 asynchronously:
89 68
90 use Fcntl;
91 use Event; 69 use EV;
92 use IO::AIO; 70 use IO::AIO;
93 71
94 # register the IO::AIO callback with Event 72 # register the IO::AIO callback with EV
95 Event->io (fd => IO::AIO::poll_fileno, 73 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 74
99 # queue the request to open /etc/passwd 75 # queue the request to open /etc/passwd
100 aio_open "/etc/passwd", O_RDONLY, 0, sub { 76 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
101 my $fh = shift 77 my $fh = shift
102 or die "error while opening: $!"; 78 or die "error while opening: $!";
103 79
104 # stat'ing filehandles is generally non-blocking 80 # stat'ing filehandles is generally non-blocking
105 my $size = -s $fh; 81 my $size = -s $fh;
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114 90
115 # file contents now in $contents 91 # file contents now in $contents
116 print $contents; 92 print $contents;
117 93
118 # exit event loop and program 94 # exit event loop and program
119 Event::unloop; 95 EV::unloop;
120 }; 96 };
121 }; 97 };
122 98
123 # possibly queue up other requests, or open GUI windows, 99 # possibly queue up other requests, or open GUI windows,
124 # check for sockets etc. etc. 100 # check for sockets etc. etc.
125 101
126 # process events as long as there are some: 102 # process events as long as there are some:
127 Event::loop; 103 EV::loop;
128 104
129REQUEST ANATOMY AND LIFETIME 105REQUEST ANATOMY AND LIFETIME
130 Every "aio_*" function creates a request. which is a C data structure 106 Every "aio_*" function creates a request. which is a C data structure
131 not directly visible to Perl. 107 not directly visible to Perl.
132 108
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168 anymore (except possibly for the Perl object, but its connection to 144 anymore (except possibly for the Perl object, but its connection to
169 the actual aio request is severed and calling its methods will 145 the actual aio request is severed and calling its methods will
170 either do nothing or result in a runtime error). 146 either do nothing or result in a runtime error).
171 147
172FUNCTIONS 148FUNCTIONS
173 AIO REQUEST FUNCTIONS 149 QUICK OVERVIEW
150 This section simply lists the prototypes most of the functions for quick
151 reference. See the following sections for function-by-function
152 documentation.
153
154 aio_wd $pathname, $callback->($wd)
155 aio_open $pathname, $flags, $mode, $callback->($fh)
156 aio_close $fh, $callback->($status)
157 aio_seek $fh,$offset,$whence, $callback->($offs)
158 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
159 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
160 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
161 aio_readahead $fh,$offset,$length, $callback->($retval)
162 aio_stat $fh_or_path, $callback->($status)
163 aio_lstat $fh, $callback->($status)
164 aio_statvfs $fh_or_path, $callback->($statvfs)
165 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
166 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
167 aio_chmod $fh_or_path, $mode, $callback->($status)
168 aio_truncate $fh_or_path, $offset, $callback->($status)
169 aio_allocate $fh, $mode, $offset, $len, $callback->($status)
170 aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
171 aio_unlink $pathname, $callback->($status)
172 aio_mknod $pathname, $mode, $dev, $callback->($status)
173 aio_link $srcpath, $dstpath, $callback->($status)
174 aio_symlink $srcpath, $dstpath, $callback->($status)
175 aio_readlink $pathname, $callback->($link)
176 aio_realpath $pathname, $callback->($link)
177 aio_rename $srcpath, $dstpath, $callback->($status)
178 aio_mkdir $pathname, $mode, $callback->($status)
179 aio_rmdir $pathname, $callback->($status)
180 aio_readdir $pathname, $callback->($entries)
181 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
182 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
183 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
184 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
185 aio_load $pathname, $data, $callback->($status)
186 aio_copy $srcpath, $dstpath, $callback->($status)
187 aio_move $srcpath, $dstpath, $callback->($status)
188 aio_rmtree $pathname, $callback->($status)
189 aio_sync $callback->($status)
190 aio_syncfs $fh, $callback->($status)
191 aio_fsync $fh, $callback->($status)
192 aio_fdatasync $fh, $callback->($status)
193 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
194 aio_pathsync $pathname, $callback->($status)
195 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
196 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
197 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
198 aio_mlockall $flags, $callback->($status)
199 aio_group $callback->(...)
200 aio_nop $callback->()
201
202 $prev_pri = aioreq_pri [$pri]
203 aioreq_nice $pri_adjust
204
205 IO::AIO::poll_wait
206 IO::AIO::poll_cb
207 IO::AIO::poll
208 IO::AIO::flush
209 IO::AIO::max_poll_reqs $nreqs
210 IO::AIO::max_poll_time $seconds
211 IO::AIO::min_parallel $nthreads
212 IO::AIO::max_parallel $nthreads
213 IO::AIO::max_idle $nthreads
214 IO::AIO::idle_timeout $seconds
215 IO::AIO::max_outstanding $maxreqs
216 IO::AIO::nreqs
217 IO::AIO::nready
218 IO::AIO::npending
219
220 IO::AIO::sendfile $ofh, $ifh, $offset, $count
221 IO::AIO::fadvise $fh, $offset, $len, $advice
222 IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
223 IO::AIO::munmap $scalar
224 IO::AIO::madvise $scalar, $offset, $length, $advice
225 IO::AIO::mprotect $scalar, $offset, $length, $protect
226 IO::AIO::munlock $scalar, $offset = 0, $length = undef
227 IO::AIO::munlockall
228
229 API NOTES
174 All the "aio_*" calls are more or less thin wrappers around the syscall 230 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 231 with the same name (sans "aio_"). The arguments are similar or
176 identical, and they all accept an additional (and optional) $callback 232 identical, and they all accept an additional (and optional) $callback
177 argument which must be a code reference. This code reference will get 233 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 234 called after the syscall has been executed in an asynchronous fashion.
179 error, unlike perl, which usually delivers "false") as it's sole 235 The results of the request will be passed as arguments to the callback
180 argument when the given syscall has been executed asynchronously. 236 (and, if an error occured, in $!) - for most requests the syscall return
237 code (e.g. most syscalls return -1 on error, unlike perl, which usually
238 delivers "false").
239
240 Some requests (such as "aio_readdir") pass the actual results and
241 communicate failures by passing "undef".
181 242
182 All functions expecting a filehandle keep a copy of the filehandle 243 All functions expecting a filehandle keep a copy of the filehandle
183 internally until the request has finished. 244 internally until the request has finished.
184 245
185 All functions return request objects of type IO::AIO::REQ that allow 246 All functions return request objects of type IO::AIO::REQ that allow
186 further manipulation of those requests while they are in-flight. 247 further manipulation of those requests while they are in-flight.
187 248
188 The pathnames you pass to these routines *must* be absolute and encoded 249 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 250 reason for this is that at the time the request is being executed, the
190 being executed, the current working directory could have changed. 251 current working directory could have changed. Alternatively, you can
191 Alternatively, you can make sure that you never change the current 252 make sure that you never change the current working directory anywhere
192 working directory anywhere in the program and then use relative paths. 253 in the program and then use relative paths. You can also take advantage
254 of IO::AIOs working directory abstraction, that lets you specify paths
255 relative to some previously-opened "working directory object" - see the
256 description of the "IO::AIO::WD" class later in this document.
193 257
194 To encode pathnames as octets, either make sure you either: a) always 258 To encode pathnames as octets, either make sure you either: a) always
195 pass in filenames you got from outside (command line, readdir etc.) 259 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 260 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 261 Encode module and encode your pathnames to the locale (or other)
198 the user environment, d) use Glib::filename_from_unicode on unicode 262 encoding in effect in the user environment, d) use
199 filenames or e) use something else to ensure your scalar has the correct 263 Glib::filename_from_unicode on unicode filenames or e) use something
200 contents. 264 else to ensure your scalar has the correct contents.
201 265
202 This works, btw. independent of the internal UTF-8 bit, which IO::AIO 266 This works, btw. independent of the internal UTF-8 bit, which IO::AIO
203 handles correctly wether it is set or not. 267 handles correctly whether it is set or not.
204 268
269 AIO REQUEST FUNCTIONS
205 $prev_pri = aioreq_pri [$pri] 270 $prev_pri = aioreq_pri [$pri]
206 Returns the priority value that would be used for the next request 271 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. 272 and, if $pri is given, sets the priority for the next aio request.
208 273
209 The default priority is 0, the minimum and maximum priorities are -4 274 The default priority is 0, the minimum and maximum priorities are -4
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231 Similar to "aioreq_pri", but subtracts the given value from the 296 Similar to "aioreq_pri", but subtracts the given value from the
232 current priority, so the effect is cumulative. 297 current priority, so the effect is cumulative.
233 298
234 aio_open $pathname, $flags, $mode, $callback->($fh) 299 aio_open $pathname, $flags, $mode, $callback->($fh)
235 Asynchronously open or create a file and call the callback with a 300 Asynchronously open or create a file and call the callback with a
236 newly created filehandle for the file. 301 newly created filehandle for the file (or "undef" in case of an
302 error).
237 303
238 The pathname passed to "aio_open" must be absolute. See API NOTES, 304 The pathname passed to "aio_open" must be absolute. See API NOTES,
239 above, for an explanation. 305 above, for an explanation.
240 306
241 The $flags argument is a bitmask. See the "Fcntl" module for a list. 307 The $flags argument is a bitmask. See the "Fcntl" module for a list.
242 They are the same as used by "sysopen". 308 They are the same as used by "sysopen".
243 309
244 Likewise, $mode specifies the mode of the newly created file, if it 310 Likewise, $mode specifies the mode of the newly created file, if it
245 didn't exist and "O_CREAT" has been given, just like perl's 311 didn't exist and "O_CREAT" has been given, just like perl's
246 "sysopen", except that it is mandatory (i.e. use 0 if you don't 312 "sysopen", except that it is mandatory (i.e. use 0 if you don't
247 create new files, and 0666 or 0777 if you do). 313 create new files, and 0666 or 0777 if you do). Note that the $mode
314 will be modified by the umask in effect then the request is being
315 executed, so better never change the umask.
248 316
249 Example: 317 Example:
250 318
251 aio_open "/etc/passwd", O_RDONLY, 0, sub { 319 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
252 if ($_[0]) { 320 if ($_[0]) {
253 print "open successful, fh is $_[0]\n"; 321 print "open successful, fh is $_[0]\n";
254 ... 322 ...
255 } else { 323 } else {
256 die "open failed: $!\n"; 324 die "open failed: $!\n";
257 } 325 }
258 }; 326 };
259 327
328 In addition to all the common open modes/flags ("O_RDONLY",
329 "O_WRONLY", "O_RDWR", "O_CREAT", "O_TRUNC", "O_EXCL" and
330 "O_APPEND"), the following POSIX and non-POSIX constants are
331 available (missing ones on your system are, as usual, 0):
332
333 "O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",
334 "O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",
335 "O_DSYNC", "O_RSYNC", "O_SYNC" and "O_TTY_INIT".
336
260 aio_close $fh, $callback->($status) 337 aio_close $fh, $callback->($status)
261 Asynchronously close a file and call the callback with the result 338 Asynchronously close a file and call the callback with the result
262 code. *WARNING:* although accepted, you should not pass in a perl 339 code.
263 filehandle here, as perl will likely close the file descriptor
264 another time when the filehandle is destroyed. Normally, you can
265 safely call perls "close" or just let filehandles go out of scope.
266 340
267 This is supposed to be a bug in the API, so that might change. It's 341 Unfortunately, you can't do this to perl. Perl *insists* very
268 therefore best to avoid this function. 342 strongly on closing the file descriptor associated with the
343 filehandle itself.
344
345 Therefore, "aio_close" will not close the filehandle - instead it
346 will use dup2 to overwrite the file descriptor with the write-end of
347 a pipe (the pipe fd will be created on demand and will be cached).
348
349 Or in other words: the file descriptor will be closed, but it will
350 not be free for reuse until the perl filehandle is closed.
351
352 aio_seek $fh, $offset, $whence, $callback->($offs)
353 Seeks the filehandle to the new $offset, similarly to perl's
354 "sysseek". The $whence can use the traditional values (0 for
355 "IO::AIO::SEEK_SET", 1 for "IO::AIO::SEEK_CUR" or 2 for
356 "IO::AIO::SEEK_END").
357
358 The resulting absolute offset will be passed to the callback, or -1
359 in case of an error.
360
361 In theory, the $whence constants could be different than the
362 corresponding values from Fcntl, but perl guarantees they are the
363 same, so don't panic.
364
365 As a GNU/Linux (and maybe Solaris) extension, also the constants
366 "IO::AIO::SEEK_DATA" and "IO::AIO::SEEK_HOLE" are available, if they
367 could be found. No guarantees about suitability for use in
368 "aio_seek" or Perl's "sysseek" can be made though, although I would
369 naively assume they "just work".
269 370
270 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 371 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
271 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 372 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
272 Reads or writes "length" bytes from the specified "fh" and "offset" 373 Reads or writes $length bytes from or to the specified $fh and
273 into the scalar given by "data" and offset "dataoffset" and calls 374 $offset into the scalar given by $data and offset $dataoffset and
274 the callback without the actual number of bytes read (or -1 on 375 calls the callback without the actual number of bytes read (or -1 on
275 error, just like the syscall). 376 error, just like the syscall).
276 377
378 "aio_read" will, like "sysread", shrink or grow the $data scalar to
379 offset plus the actual number of bytes read.
380
381 If $offset is undefined, then the current file descriptor offset
382 will be used (and updated), otherwise the file descriptor offset
383 will not be changed by these calls.
384
385 If $length is undefined in "aio_write", use the remaining length of
386 $data.
387
388 If $dataoffset is less than zero, it will be counted from the end of
389 $data.
390
277 The $data scalar *MUST NOT* be modified in any way while the request 391 The $data scalar *MUST NOT* be modified in any way while the request
278 is outstanding. Modifying it can result in segfaults or WW3 (if the 392 is outstanding. Modifying it can result in segfaults or World War
279 necessary/optional hardware is installed). 393 III (if the necessary/optional hardware is installed).
280 394
281 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at 395 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
282 offset 0 within the scalar: 396 offset 0 within the scalar:
283 397
284 aio_read $fh, 7, 15, $buffer, 0, sub { 398 aio_read $fh, 7, 15, $buffer, 0, sub {
… …
289 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 403 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
290 Tries to copy $length bytes from $in_fh to $out_fh. It starts 404 Tries to copy $length bytes from $in_fh to $out_fh. It starts
291 reading at byte offset $in_offset, and starts writing at the current 405 reading at byte offset $in_offset, and starts writing at the current
292 file offset of $out_fh. Because of that, it is not safe to issue 406 file offset of $out_fh. Because of that, it is not safe to issue
293 more than one "aio_sendfile" per $out_fh, as they will interfere 407 more than one "aio_sendfile" per $out_fh, as they will interfere
294 with each other. 408 with each other. The same $in_fh works fine though, as this function
409 does not move or use the file offset of $in_fh.
295 410
411 Please note that "aio_sendfile" can read more bytes from $in_fh than
412 are written, and there is no way to find out how many more bytes
413 have been read from "aio_sendfile" alone, as "aio_sendfile" only
414 provides the number of bytes written to $out_fh. Only if the result
415 value equals $length one can assume that $length bytes have been
416 read.
417
418 Unlike with other "aio_" functions, it makes a lot of sense to use
419 "aio_sendfile" on non-blocking sockets, as long as one end
420 (typically the $in_fh) is a file - the file I/O will then be
421 asynchronous, while the socket I/O will be non-blocking. Note,
422 however, that you can run into a trap where "aio_sendfile" reads
423 some data with readahead, then fails to write all data, and when the
424 socket is ready the next time, the data in the cache is already
425 lost, forcing "aio_sendfile" to again hit the disk. Explicit
426 "aio_read" + "aio_write" let's you better control resource usage.
427
296 This call tries to make use of a native "sendfile" syscall to 428 This call tries to make use of a native "sendfile"-like syscall to
297 provide zero-copy operation. For this to work, $out_fh should refer 429 provide zero-copy operation. For this to work, $out_fh should refer
298 to a socket, and $in_fh should refer to mmap'able file. 430 to a socket, and $in_fh should refer to an mmap'able file.
299 431
300 If the native sendfile call fails or is not implemented, it will be 432 If a native sendfile cannot be found or it fails with "ENOSYS",
301 emulated, so you can call "aio_sendfile" on any type of filehandle 433 "EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
302 regardless of the limitations of the operating system. 434 "ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on
435 any type of filehandle regardless of the limitations of the
436 operating system.
303 437
304 Please note, however, that "aio_sendfile" can read more bytes from 438 As native sendfile syscalls (as practically any non-POSIX interface
305 $in_fh than are written, and there is no way to find out how many 439 hacked together in a hurry to improve benchmark numbers) tend to be
306 bytes have been read from "aio_sendfile" alone, as "aio_sendfile" 440 rather buggy on many systems, this implementation tries to work
307 only provides the number of bytes written to $out_fh. Only if the 441 around some known bugs in Linux and FreeBSD kernels (probably
308 result value equals $length one can assume that $length bytes have 442 others, too), but that might fail, so you really really should check
309 been read. 443 the return value of "aio_sendfile" - fewre bytes than expected might
444 have been transferred.
310 445
311 aio_readahead $fh,$offset,$length, $callback->($retval) 446 aio_readahead $fh,$offset,$length, $callback->($retval)
312 "aio_readahead" populates the page cache with data from a file so 447 "aio_readahead" populates the page cache with data from a file so
313 that subsequent reads from that file will not block on disk I/O. The 448 that subsequent reads from that file will not block on disk I/O. The
314 $offset argument specifies the starting point from which data is to 449 $offset argument specifies the starting point from which data is to
… …
335 Currently, the stats are always 64-bit-stats, i.e. instead of 470 Currently, the stats are always 64-bit-stats, i.e. instead of
336 returning an error when stat'ing a large file, the results will be 471 returning an error when stat'ing a large file, the results will be
337 silently truncated unless perl itself is compiled with large file 472 silently truncated unless perl itself is compiled with large file
338 support. 473 support.
339 474
475 To help interpret the mode and dev/rdev stat values, IO::AIO offers
476 the following constants and functions (if not implemented, the
477 constants will be 0 and the functions will either "croak" or fall
478 back on traditional behaviour).
479
480 "S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
481 "S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
482 "IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
483
340 Example: Print the length of /etc/passwd: 484 Example: Print the length of /etc/passwd:
341 485
342 aio_stat "/etc/passwd", sub { 486 aio_stat "/etc/passwd", sub {
343 $_[0] and die "stat failed: $!"; 487 $_[0] and die "stat failed: $!";
344 print "size is ", -s _, "\n"; 488 print "size is ", -s _, "\n";
345 }; 489 };
346 490
491 aio_statvfs $fh_or_path, $callback->($statvfs)
492 Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
493 whether a file handle or path was passed.
494
495 On success, the callback is passed a hash reference with the
496 following members: "bsize", "frsize", "blocks", "bfree", "bavail",
497 "files", "ffree", "favail", "fsid", "flag" and "namemax". On
498 failure, "undef" is passed.
499
500 The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
501 and "ST_NOSUID".
502
503 The following non-POSIX IO::AIO::ST_* flag masks are defined to
504 their correct value when available, or to 0 on systems that do not
505 support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
506 "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
507 "ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
508
509 Example: stat "/wd" and dump out the data if successful.
510
511 aio_statvfs "/wd", sub {
512 my $f = $_[0]
513 or die "statvfs: $!";
514
515 use Data::Dumper;
516 say Dumper $f;
517 };
518
519 # result:
520 {
521 bsize => 1024,
522 bfree => 4333064312,
523 blocks => 10253828096,
524 files => 2050765568,
525 flag => 4096,
526 favail => 2042092649,
527 bavail => 4333064312,
528 ffree => 2042092649,
529 namemax => 255,
530 frsize => 1024,
531 fsid => 1810
532 }
533
534 Here is a (likely partial - send me updates!) list of fsid values
535 used by Linux - it is safe to hardcode these when $^O is "linux":
536
537 0x0000adf5 adfs
538 0x0000adff affs
539 0x5346414f afs
540 0x09041934 anon-inode filesystem
541 0x00000187 autofs
542 0x42465331 befs
543 0x1badface bfs
544 0x42494e4d binfmt_misc
545 0x9123683e btrfs
546 0x0027e0eb cgroupfs
547 0xff534d42 cifs
548 0x73757245 coda
549 0x012ff7b7 coh
550 0x28cd3d45 cramfs
551 0x453dcd28 cramfs-wend (wrong endianness)
552 0x64626720 debugfs
553 0x00001373 devfs
554 0x00001cd1 devpts
555 0x0000f15f ecryptfs
556 0x00414a53 efs
557 0x0000137d ext
558 0x0000ef53 ext2/ext3
559 0x0000ef51 ext2
560 0x00004006 fat
561 0x65735546 fuseblk
562 0x65735543 fusectl
563 0x0bad1dea futexfs
564 0x01161970 gfs2
565 0x47504653 gpfs
566 0x00004244 hfs
567 0xf995e849 hpfs
568 0x958458f6 hugetlbfs
569 0x2bad1dea inotifyfs
570 0x00009660 isofs
571 0x000072b6 jffs2
572 0x3153464a jfs
573 0x6b414653 k-afs
574 0x0bd00bd0 lustre
575 0x0000137f minix
576 0x0000138f minix 30 char names
577 0x00002468 minix v2
578 0x00002478 minix v2 30 char names
579 0x00004d5a minix v3
580 0x19800202 mqueue
581 0x00004d44 msdos
582 0x0000564c novell
583 0x00006969 nfs
584 0x6e667364 nfsd
585 0x00003434 nilfs
586 0x5346544e ntfs
587 0x00009fa1 openprom
588 0x7461636F ocfs2
589 0x00009fa0 proc
590 0x6165676c pstorefs
591 0x0000002f qnx4
592 0x858458f6 ramfs
593 0x52654973 reiserfs
594 0x00007275 romfs
595 0x67596969 rpc_pipefs
596 0x73636673 securityfs
597 0xf97cff8c selinux
598 0x0000517b smb
599 0x534f434b sockfs
600 0x73717368 squashfs
601 0x62656572 sysfs
602 0x012ff7b6 sysv2
603 0x012ff7b5 sysv4
604 0x01021994 tmpfs
605 0x15013346 udf
606 0x00011954 ufs
607 0x54190100 ufs byteswapped
608 0x00009fa2 usbdevfs
609 0x01021997 v9fs
610 0xa501fcf5 vxfs
611 0xabba1974 xenfs
612 0x012ff7b4 xenix
613 0x58465342 xfs
614 0x012fd16d xia
615
616 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
617 Works like perl's "utime" function (including the special case of
618 $atime and $mtime being undef). Fractional times are supported if
619 the underlying syscalls support them.
620
621 When called with a pathname, uses utimes(2) if available, otherwise
622 utime(2). If called on a file descriptor, uses futimes(2) if
623 available, otherwise returns ENOSYS, so this is not portable.
624
625 Examples:
626
627 # set atime and mtime to current time (basically touch(1)):
628 aio_utime "path", undef, undef;
629 # set atime to current time and mtime to beginning of the epoch:
630 aio_utime "path", time, undef; # undef==0
631
632 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
633 Works like perl's "chown" function, except that "undef" for either
634 $uid or $gid is being interpreted as "do not change" (but -1 can
635 also be used).
636
637 Examples:
638
639 # same as "chown root path" in the shell:
640 aio_chown "path", 0, -1;
641 # same as above:
642 aio_chown "path", 0, undef;
643
644 aio_truncate $fh_or_path, $offset, $callback->($status)
645 Works like truncate(2) or ftruncate(2).
646
647 aio_allocate $fh, $mode, $offset, $len, $callback->($status)
648 Allocates or freed disk space according to the $mode argument. See
649 the linux "fallocate" docuemntation for details.
650
651 $mode can currently be 0 or "IO::AIO::FALLOC_FL_KEEP_SIZE" to
652 allocate space, or "IO::AIO::FALLOC_FL_PUNCH_HOLE |
653 IO::AIO::FALLOC_FL_KEEP_SIZE", to deallocate a file range.
654
655 The file system block size used by "fallocate" is presumably the
656 "f_bsize" returned by "statvfs".
657
658 If "fallocate" isn't available or cannot be emulated (currently no
659 emulation will be attempted), passes -1 and sets $! to "ENOSYS".
660
661 aio_chmod $fh_or_path, $mode, $callback->($status)
662 Works like perl's "chmod" function.
663
347 aio_unlink $pathname, $callback->($status) 664 aio_unlink $pathname, $callback->($status)
348 Asynchronously unlink (delete) a file and call the callback with the 665 Asynchronously unlink (delete) a file and call the callback with the
349 result code. 666 result code.
350 667
351 aio_mknod $path, $mode, $dev, $callback->($status) 668 aio_mknod $pathname, $mode, $dev, $callback->($status)
352 [EXPERIMENTAL] 669 [EXPERIMENTAL]
353 670
354 Asynchronously create a device node (or fifo). See mknod(2). 671 Asynchronously create a device node (or fifo). See mknod(2).
355 672
356 The only (POSIX-) portable way of calling this function is: 673 The only (POSIX-) portable way of calling this function is:
357 674
358 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... 675 aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
676
677 See "aio_stat" for info about some potentially helpful extra
678 constants and functions.
359 679
360 aio_link $srcpath, $dstpath, $callback->($status) 680 aio_link $srcpath, $dstpath, $callback->($status)
361 Asynchronously create a new link to the existing object at $srcpath 681 Asynchronously create a new link to the existing object at $srcpath
362 at the path $dstpath and call the callback with the result code. 682 at the path $dstpath and call the callback with the result code.
363 683
364 aio_symlink $srcpath, $dstpath, $callback->($status) 684 aio_symlink $srcpath, $dstpath, $callback->($status)
365 Asynchronously create a new symbolic link to the existing object at 685 Asynchronously create a new symbolic link to the existing object at
366 $srcpath at the path $dstpath and call the callback with the result 686 $srcpath at the path $dstpath and call the callback with the result
367 code. 687 code.
368 688
369 aio_readlink $path, $callback->($link) 689 aio_readlink $pathname, $callback->($link)
370 Asynchronously read the symlink specified by $path and pass it to 690 Asynchronously read the symlink specified by $path and pass it to
371 the callback. If an error occurs, nothing or undef gets passed to 691 the callback. If an error occurs, nothing or undef gets passed to
372 the callback. 692 the callback.
373 693
694 aio_realpath $pathname, $callback->($path)
695 Asynchronously make the path absolute and resolve any symlinks in
696 $path. The resulting path only consists of directories (same as
697 Cwd::realpath).
698
699 This request can be used to get the absolute path of the current
700 working directory by passing it a path of . (a single dot).
701
374 aio_rename $srcpath, $dstpath, $callback->($status) 702 aio_rename $srcpath, $dstpath, $callback->($status)
375 Asynchronously rename the object at $srcpath to $dstpath, just as 703 Asynchronously rename the object at $srcpath to $dstpath, just as
376 rename(2) and call the callback with the result code. 704 rename(2) and call the callback with the result code.
377 705
706 On systems that support the AIO::WD working directory abstraction
707 natively, the case "[$wd, "."]" as $srcpath is specialcased -
708 instead of failing, "rename" is called on the absolute path of $wd.
709
710 aio_mkdir $pathname, $mode, $callback->($status)
711 Asynchronously mkdir (create) a directory and call the callback with
712 the result code. $mode will be modified by the umask at the time the
713 request is executed, so do not change your umask.
714
378 aio_rmdir $pathname, $callback->($status) 715 aio_rmdir $pathname, $callback->($status)
379 Asynchronously rmdir (delete) a directory and call the callback with 716 Asynchronously rmdir (delete) a directory and call the callback with
380 the result code. 717 the result code.
718
719 On systems that support the AIO::WD working directory abstraction
720 natively, the case "[$wd, "."]" is specialcased - instead of
721 failing, "rmdir" is called on the absolute path of $wd.
381 722
382 aio_readdir $pathname, $callback->($entries) 723 aio_readdir $pathname, $callback->($entries)
383 Unlike the POSIX call of the same name, "aio_readdir" reads an 724 Unlike the POSIX call of the same name, "aio_readdir" reads an
384 entire directory (i.e. opendir + readdir + closedir). The entries 725 entire directory (i.e. opendir + readdir + closedir). The entries
385 will not be sorted, and will NOT include the "." and ".." entries. 726 will not be sorted, and will NOT include the "." and ".." entries.
386 727
387 The callback a single argument which is either "undef" or an 728 The callback is passed a single argument which is either "undef" or
388 array-ref with the filenames. 729 an array-ref with the filenames.
389 730
731 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
732 Quite similar to "aio_readdir", but the $flags argument allows one
733 to tune behaviour and output format. In case of an error, $entries
734 will be "undef".
735
736 The flags are a combination of the following constants, ORed
737 together (the flags will also be passed to the callback, possibly
738 modified):
739
740 IO::AIO::READDIR_DENTS
741 When this flag is off, then the callback gets an arrayref
742 consisting of names only (as with "aio_readdir"), otherwise it
743 gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
744 describing a single directory entry in more detail.
745
746 $name is the name of the entry.
747
748 $type is one of the "IO::AIO::DT_xxx" constants:
749
750 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
751 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
752 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
753
754 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
755 you need to know, you have to run stat yourself. Also, for speed
756 reasons, the $type scalars are read-only: you can not modify
757 them.
758
759 $inode is the inode number (which might not be exact on systems
760 with 64 bit inode numbers and 32 bit perls). This field has
761 unspecified content on systems that do not deliver the inode
762 information.
763
764 IO::AIO::READDIR_DIRS_FIRST
765 When this flag is set, then the names will be returned in an
766 order where likely directories come first, in optimal stat
767 order. This is useful when you need to quickly find directories,
768 or you want to find all directories while avoiding to stat()
769 each entry.
770
771 If the system returns type information in readdir, then this is
772 used to find directories directly. Otherwise, likely directories
773 are names beginning with ".", or otherwise names with no dots,
774 of which names with short names are tried first.
775
776 IO::AIO::READDIR_STAT_ORDER
777 When this flag is set, then the names will be returned in an
778 order suitable for stat()'ing each one. That is, when you plan
779 to stat() all files in the given directory, then the returned
780 order will likely be fastest.
781
782 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
783 specified, then the likely dirs come first, resulting in a less
784 optimal stat order.
785
786 IO::AIO::READDIR_FOUND_UNKNOWN
787 This flag should not be set when calling "aio_readdirx".
788 Instead, it is being set by "aio_readdirx", when any of the
789 $type's found were "IO::AIO::DT_UNKNOWN". The absence of this
790 flag therefore indicates that all $type's are known, which can
791 be used to speed up some algorithms.
792
390 aio_load $path, $data, $callback->($status) 793 aio_load $pathname, $data, $callback->($status)
391 This is a composite request that tries to fully load the given file 794 This is a composite request that tries to fully load the given file
392 into memory. Status is the same as with aio_read. 795 into memory. Status is the same as with aio_read.
393 796
394 aio_copy $srcpath, $dstpath, $callback->($status) 797 aio_copy $srcpath, $dstpath, $callback->($status)
395 Try to copy the *file* (directories not supported as either source 798 Try to copy the *file* (directories not supported as either source
396 or destination) from $srcpath to $dstpath and call the callback with 799 or destination) from $srcpath to $dstpath and call the callback with
397 the 0 (error) or -1 ok. 800 a status of 0 (ok) or -1 (error, see $!).
398 801
399 This is a composite request that it creates the destination file 802 This is a composite request that creates the destination file with
400 with mode 0200 and copies the contents of the source file into it 803 mode 0200 and copies the contents of the source file into it using
401 using "aio_sendfile", followed by restoring atime, mtime, access 804 "aio_sendfile", followed by restoring atime, mtime, access mode and
402 mode and uid/gid, in that order. 805 uid/gid, in that order.
403 806
404 If an error occurs, the partial destination file will be unlinked, 807 If an error occurs, the partial destination file will be unlinked,
405 if possible, except when setting atime, mtime, access mode and 808 if possible, except when setting atime, mtime, access mode and
406 uid/gid, where errors are being ignored. 809 uid/gid, where errors are being ignored.
407 810
408 aio_move $srcpath, $dstpath, $callback->($status) 811 aio_move $srcpath, $dstpath, $callback->($status)
409 Try to move the *file* (directories not supported as either source 812 Try to move the *file* (directories not supported as either source
410 or destination) from $srcpath to $dstpath and call the callback with 813 or destination) from $srcpath to $dstpath and call the callback with
411 the 0 (error) or -1 ok. 814 a status of 0 (ok) or -1 (error, see $!).
412 815
413 This is a composite request that tries to rename(2) the file first. 816 This is a composite request that tries to rename(2) the file first;
414 If rename files with "EXDEV", it copies the file with "aio_copy" 817 if rename fails with "EXDEV", it copies the file with "aio_copy"
415 and, if that is successful, unlinking the $srcpath. 818 and, if that is successful, unlinks the $srcpath.
416 819
417 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 820 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
418 Scans a directory (similar to "aio_readdir") but additionally tries 821 Scans a directory (similar to "aio_readdir") but additionally tries
419 to efficiently separate the entries of directory $path into two sets 822 to efficiently separate the entries of directory $path into two sets
420 of names, directories you can recurse into (directories), and ones 823 of names, directories you can recurse into (directories), and ones
421 you cannot recurse into (everything else, including symlinks to 824 you cannot recurse into (everything else, including symlinks to
422 directories). 825 directories).
… …
440 Implementation notes. 843 Implementation notes.
441 844
442 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry 845 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
443 can. 846 can.
444 847
848 If readdir returns file type information, then this is used directly
849 to find directories.
850
445 After reading the directory, the modification time, size etc. of the 851 Otherwise, after reading the directory, the modification time, size
446 directory before and after the readdir is checked, and if they match 852 etc. of the directory before and after the readdir is checked, and
447 (and isn't the current time), the link count will be used to decide 853 if they match (and isn't the current time), the link count will be
448 how many entries are directories (if >= 2). Otherwise, no knowledge 854 used to decide how many entries are directories (if >= 2).
449 of the number of subdirectories will be assumed. 855 Otherwise, no knowledge of the number of subdirectories will be
856 assumed.
450 857
451 Then entries will be sorted into likely directories (everything 858 Then entries will be sorted into likely directories a non-initial
452 without a non-initial dot currently) and likely non-directories 859 dot currently) and likely non-directories (see "aio_readdirx"). Then
453 (everything else). Then every entry plus an appended "/." will be 860 every entry plus an appended "/." will be "stat"'ed, likely
454 "stat"'ed, likely directories first. If that succeeds, it assumes 861 directories first, in order of their inode numbers. If that
455 that the entry is a directory or a symlink to directory (which will 862 succeeds, it assumes that the entry is a directory or a symlink to
456 be checked seperately). This is often faster than stat'ing the entry 863 directory (which will be checked separately). This is often faster
457 itself because filesystems might detect the type of the entry 864 than stat'ing the entry itself because filesystems might detect the
458 without reading the inode data (e.g. ext2fs filetype feature). 865 type of the entry without reading the inode data (e.g. ext2fs
866 filetype feature), even on systems that cannot return the filetype
867 information on readdir.
459 868
460 If the known number of directories (link count - 2) has been 869 If the known number of directories (link count - 2) has been
461 reached, the rest of the entries is assumed to be non-directories. 870 reached, the rest of the entries is assumed to be non-directories.
462 871
463 This only works with certainty on POSIX (= UNIX) filesystems, which 872 This only works with certainty on POSIX (= UNIX) filesystems, which
… …
465 874
466 It will also likely work on non-POSIX filesystems with reduced 875 It will also likely work on non-POSIX filesystems with reduced
467 efficiency as those tend to return 0 or 1 as link counts, which 876 efficiency as those tend to return 0 or 1 as link counts, which
468 disables the directory counting heuristic. 877 disables the directory counting heuristic.
469 878
879 aio_rmtree $pathname, $callback->($status)
880 Delete a directory tree starting (and including) $path, return the
881 status of the final "rmdir" only. This is a composite request that
882 uses "aio_scandir" to recurse into and rmdir directories, and unlink
883 everything else.
884
885 aio_sync $callback->($status)
886 Asynchronously call sync and call the callback when finished.
887
470 aio_fsync $fh, $callback->($status) 888 aio_fsync $fh, $callback->($status)
471 Asynchronously call fsync on the given filehandle and call the 889 Asynchronously call fsync on the given filehandle and call the
472 callback with the fsync result code. 890 callback with the fsync result code.
473 891
474 aio_fdatasync $fh, $callback->($status) 892 aio_fdatasync $fh, $callback->($status)
475 Asynchronously call fdatasync on the given filehandle and call the 893 Asynchronously call fdatasync on the given filehandle and call the
476 callback with the fdatasync result code. 894 callback with the fdatasync result code.
477 895
478 If this call isn't available because your OS lacks it or it couldn't 896 If this call isn't available because your OS lacks it or it couldn't
479 be detected, it will be emulated by calling "fsync" instead. 897 be detected, it will be emulated by calling "fsync" instead.
898
899 aio_syncfs $fh, $callback->($status)
900 Asynchronously call the syncfs syscall to sync the filesystem
901 associated to the given filehandle and call the callback with the
902 syncfs result code. If syncfs is not available, calls sync(), but
903 returns -1 and sets errno to "ENOSYS" nevertheless.
904
905 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
906 Sync the data portion of the file specified by $offset and $length
907 to disk (but NOT the metadata), by calling the Linux-specific
908 sync_file_range call. If sync_file_range is not available or it
909 returns ENOSYS, then fdatasync or fsync is being substituted.
910
911 $flags can be a combination of
912 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
913 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
914 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
915 manpage for details.
916
917 aio_pathsync $pathname, $callback->($status)
918 This request tries to open, fsync and close the given path. This is
919 a composite request intended to sync directories after directory
920 operations (E.g. rename). This might not work on all operating
921 systems or have any specific effect, but usually it makes sure that
922 directory changes get written to disc. It works for anything that
923 can be opened for read-only, not just directories.
924
925 Future versions of this function might fall back to other methods
926 when "fsync" on the directory fails (such as calling "sync").
927
928 Passes 0 when everything went ok, and -1 on error.
929
930 aio_msync $scalar, $offset = 0, $length = undef, flags = 0,
931 $callback->($status)
932 This is a rather advanced IO::AIO call, which only works on
933 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
934 also works on data scalars managed by the Sys::Mmap or Mmap modules,
935 note that the scalar must only be modified in-place while an aio
936 operation is pending on it).
937
938 It calls the "msync" function of your OS, if available, with the
939 memory area starting at $offset in the string and ending $length
940 bytes later. If $length is negative, counts from the end, and if
941 $length is "undef", then it goes till the end of the string. The
942 flags can be a combination of "IO::AIO::MS_ASYNC",
943 "IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC".
944
945 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
946 $callback->($status)
947 This is a rather advanced IO::AIO call, which works best on
948 mmap(2)ed scalars.
949
950 It touches (reads or writes) all memory pages in the specified range
951 inside the scalar. All caveats and parameters are the same as for
952 "aio_msync", above, except for flags, which must be either 0 (which
953 reads all pages and ensures they are instantiated) or
954 "IO::AIO::MT_MODIFY", which modifies the memory pages (by reading
955 and writing an octet from it, which dirties the page).
956
957 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
958 This is a rather advanced IO::AIO call, which works best on
959 mmap(2)ed scalars.
960
961 It reads in all the pages of the underlying storage into memory (if
962 any) and locks them, so they are not getting swapped/paged out or
963 removed.
964
965 If $length is undefined, then the scalar will be locked till the
966 end.
967
968 On systems that do not implement "mlock", this function returns -1
969 and sets errno to "ENOSYS".
970
971 Note that the corresponding "munlock" is synchronous and is
972 documented under "MISCELLANEOUS FUNCTIONS".
973
974 Example: open a file, mmap and mlock it - both will be undone when
975 $data gets destroyed.
976
977 open my $fh, "<", $path or die "$path: $!";
978 my $data;
979 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
980 aio_mlock $data; # mlock in background
981
982 aio_mlockall $flags, $callback->($status)
983 Calls the "mlockall" function with the given $flags (a combination
984 of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
985
986 On systems that do not implement "mlockall", this function returns
987 -1 and sets errno to "ENOSYS".
988
989 Note that the corresponding "munlockall" is synchronous and is
990 documented under "MISCELLANEOUS FUNCTIONS".
991
992 Example: asynchronously lock all current and future pages into
993 memory.
994
995 aio_mlockall IO::AIO::MCL_FUTURE;
996
997 aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
998 Queries the extents of the given file (by calling the Linux "FIEMAP"
999 ioctl, see <http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for
1000 details). If the ioctl is not available on your OS, then this
1001 request will fail with "ENOSYS".
1002
1003 $start is the starting offset to query extents for, $length is the
1004 size of the range to query - if it is "undef", then the whole file
1005 will be queried.
1006
1007 $flags is a combination of flags ("IO::AIO::FIEMAP_FLAG_SYNC" or
1008 "IO::AIO::FIEMAP_FLAG_XATTR" - "IO::AIO::FIEMAP_FLAGS_COMPAT" is
1009 also exported), and is normally 0 or "IO::AIO::FIEMAP_FLAG_SYNC" to
1010 query the data portion.
1011
1012 $count is the maximum number of extent records to return. If it is
1013 "undef", then IO::AIO queries all extents of the range. As a very
1014 special case, if it is 0, then the callback receives the number of
1015 extents instead of the extents themselves (which is unreliable, see
1016 below).
1017
1018 If an error occurs, the callback receives no arguments. The special
1019 "errno" value "IO::AIO::EBADR" is available to test for flag errors.
1020
1021 Otherwise, the callback receives an array reference with extent
1022 structures. Each extent structure is an array reference itself, with
1023 the following members:
1024
1025 [$logical, $physical, $length, $flags]
1026
1027 Flags is any combination of the following flag values (typically
1028 either 0 or "IO::AIO::FIEMAP_EXTENT_LAST" (1)):
1029
1030 "IO::AIO::FIEMAP_EXTENT_LAST", "IO::AIO::FIEMAP_EXTENT_UNKNOWN",
1031 "IO::AIO::FIEMAP_EXTENT_DELALLOC", "IO::AIO::FIEMAP_EXTENT_ENCODED",
1032 "IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED",
1033 "IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED",
1034 "IO::AIO::FIEMAP_EXTENT_DATA_INLINE",
1035 "IO::AIO::FIEMAP_EXTENT_DATA_TAIL",
1036 "IO::AIO::FIEMAP_EXTENT_UNWRITTEN", "IO::AIO::FIEMAP_EXTENT_MERGED"
1037 or "IO::AIO::FIEMAP_EXTENT_SHARED".
1038
1039 At the time of this writing (Linux 3.2), this requets is unreliable
1040 unless $count is "undef", as the kernel has all sorts of bugs
1041 preventing it to return all extents of a range for files with large
1042 number of extents. The code works around all these issues if $count
1043 is undef.
480 1044
481 aio_group $callback->(...) 1045 aio_group $callback->(...)
482 This is a very special aio request: Instead of doing something, it 1046 This is a very special aio request: Instead of doing something, it
483 is a container for other aio requests, which is useful if you want 1047 is a container for other aio requests, which is useful if you want
484 to bundle many requests into a single, composite, request with a 1048 to bundle many requests into a single, composite, request with a
… …
519 requests like sleep and file handle readable/writable, the overhead 1083 requests like sleep and file handle readable/writable, the overhead
520 this creates is immense (it blocks a thread for a long time) so do 1084 this creates is immense (it blocks a thread for a long time) so do
521 not use this function except to put your application under 1085 not use this function except to put your application under
522 artificial I/O pressure. 1086 artificial I/O pressure.
523 1087
1088 IO::AIO::WD - multiple working directories
1089 Your process only has one current working directory, which is used by
1090 all threads. This makes it hard to use relative paths (some other
1091 component could call "chdir" at any time, and it is hard to control when
1092 the path will be used by IO::AIO).
1093
1094 One solution for this is to always use absolute paths. This usually
1095 works, but can be quite slow (the kernel has to walk the whole path on
1096 every access), and can also be a hassle to implement.
1097
1098 Newer POSIX systems have a number of functions (openat, fdopendir,
1099 futimensat and so on) that make it possible to specify working
1100 directories per operation.
1101
1102 For portability, and because the clowns who "designed", or shall I
1103 write, perpetrated this new interface were obviously half-drunk, this
1104 abstraction cannot be perfect, though.
1105
1106 IO::AIO allows you to convert directory paths into a so-called
1107 IO::AIO::WD object. This object stores the canonicalised, absolute
1108 version of the path, and on systems that allow it, also a directory file
1109 descriptor.
1110
1111 Everywhere where a pathname is accepted by IO::AIO (e.g. in "aio_stat"
1112 or "aio_unlink"), one can specify an array reference with an IO::AIO::WD
1113 object and a pathname instead (or the IO::AIO::WD object alone, which
1114 gets interpreted as "[$wd, "."]"). If the pathname is absolute, the
1115 IO::AIO::WD object is ignored, otherwise the pathname is resolved
1116 relative to that IO::AIO::WD object.
1117
1118 For example, to get a wd object for /etc and then stat passwd inside,
1119 you would write:
1120
1121 aio_wd "/etc", sub {
1122 my $etcdir = shift;
1123
1124 # although $etcdir can be undef on error, there is generally no reason
1125 # to check for errors here, as aio_stat will fail with ENOENT
1126 # when $etcdir is undef.
1127
1128 aio_stat [$etcdir, "passwd"], sub {
1129 # yay
1130 };
1131 };
1132
1133 That "aio_wd" is a request and not a normal function shows that creating
1134 an IO::AIO::WD object is itself a potentially blocking operation, which
1135 is why it is done asynchronously.
1136
1137 To stat the directory obtained with "aio_wd" above, one could write
1138 either of the following three request calls:
1139
1140 aio_lstat "/etc" , sub { ... # pathname as normal string
1141 aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
1142 aio_lstat $wd , sub { ... # shorthand for the previous
1143
1144 As with normal pathnames, IO::AIO keeps a copy of the working directory
1145 object and the pathname string, so you could write the following without
1146 causing any issues due to $path getting reused:
1147
1148 my $path = [$wd, undef];
1149
1150 for my $name (qw(abc def ghi)) {
1151 $path->[1] = $name;
1152 aio_stat $path, sub {
1153 # ...
1154 };
1155 }
1156
1157 There are some caveats: when directories get renamed (or deleted), the
1158 pathname string doesn't change, so will point to the new directory (or
1159 nowhere at all), while the directory fd, if available on the system,
1160 will still point to the original directory. Most functions accepting a
1161 pathname will use the directory fd on newer systems, and the string on
1162 older systems. Some functions (such as realpath) will always rely on the
1163 string form of the pathname.
1164
1165 So this functionality is mainly useful to get some protection against
1166 "chdir", to easily get an absolute path out of a relative path for
1167 future reference, and to speed up doing many operations in the same
1168 directory (e.g. when stat'ing all files in a directory).
1169
1170 The following functions implement this working directory abstraction:
1171
1172 aio_wd $pathname, $callback->($wd)
1173 Asynchonously canonicalise the given pathname and convert it to an
1174 IO::AIO::WD object representing it. If possible and supported on the
1175 system, also open a directory fd to speed up pathname resolution
1176 relative to this working directory.
1177
1178 If something goes wrong, then "undef" is passwd to the callback
1179 instead of a working directory object and $! is set appropriately.
1180 Since passing "undef" as working directory component of a pathname
1181 fails the request with "ENOENT", there is often no need for error
1182 checking in the "aio_wd" callback, as future requests using the
1183 value will fail in the expected way.
1184
1185 IO::AIO::CWD
1186 This is a compiletime constant (object) that represents the process
1187 current working directory.
1188
1189 Specifying this object as working directory object for a pathname is
1190 as if the pathname would be specified directly, without a directory
1191 object. For example, these calls are functionally identical:
1192
1193 aio_stat "somefile", sub { ... };
1194 aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
1195
1196 To recover the path associated with an IO::AIO::WD object, you can use
1197 "aio_realpath":
1198
1199 aio_realpath $wd, sub {
1200 warn "path is $_[0]\n";
1201 };
1202
1203 Currently, "aio_statvfs" always, and "aio_rename" and "aio_rmdir"
1204 sometimes, fall back to using an absolue path.
1205
524 IO::AIO::REQ CLASS 1206 IO::AIO::REQ CLASS
525 All non-aggregate "aio_*" functions return an object of this class when 1207 All non-aggregate "aio_*" functions return an object of this class when
526 called in non-void context. 1208 called in non-void context.
527 1209
528 cancel $req 1210 cancel $req
529 Cancels the request, if possible. Has the effect of skipping 1211 Cancels the request, if possible. Has the effect of skipping
530 execution when entering the execute state and skipping calling the 1212 execution when entering the execute state and skipping calling the
531 callback when entering the the result state, but will leave the 1213 callback when entering the the result state, but will leave the
532 request otherwise untouched. That means that requests that currently 1214 request otherwise untouched (with the exception of readdir). That
533 execute will not be stopped and resources held by the request will 1215 means that requests that currently execute will not be stopped and
534 not be freed prematurely. 1216 resources held by the request will not be freed prematurely.
535 1217
536 cb $req $callback->(...) 1218 cb $req $callback->(...)
537 Replace (or simply set) the callback registered to the request. 1219 Replace (or simply set) the callback registered to the request.
538 1220
539 IO::AIO::GRP CLASS 1221 IO::AIO::GRP CLASS
… …
566 }; 1248 };
567 1249
568 This makes it very easy to create composite requests (see the source of 1250 This makes it very easy to create composite requests (see the source of
569 "aio_move" for an application) that work and feel like simple requests. 1251 "aio_move" for an application) that work and feel like simple requests.
570 1252
571 * The IO::AIO::GRP objects will be cleaned up during calls to 1253 * The IO::AIO::GRP objects will be cleaned up during calls to
572 "IO::AIO::poll_cb", just like any other request. 1254 "IO::AIO::poll_cb", just like any other request.
1255
573 * They can be canceled like any other request. Canceling will cancel not 1256 * They can be canceled like any other request. Canceling will cancel
574 only the request itself, but also all requests it contains. 1257 not only the request itself, but also all requests it contains.
1258
575 * They can also can also be added to other IO::AIO::GRP objects. 1259 * They can also can also be added to other IO::AIO::GRP objects.
1260
576 * You must not add requests to a group from within the group callback 1261 * You must not add requests to a group from within the group callback
577 (or any later time). 1262 (or any later time).
578 1263
579 Their lifetime, simplified, looks like this: when they are empty, they 1264 Their lifetime, simplified, looks like this: when they are empty, they
580 will finish very quickly. If they contain only requests that are in the 1265 will finish very quickly. If they contain only requests that are in the
581 "done" state, they will also finish. Otherwise they will continue to 1266 "done" state, they will also finish. Otherwise they will continue to
582 exist. 1267 exist.
583 1268
584 That means after creating a group you have some time to add requests. 1269 That means after creating a group you have some time to add requests
585 And in the callbacks of those requests, you can add further requests to 1270 (precisely before the callback has been invoked, which is only done
586 the group. And only when all those requests have finished will the the 1271 within the "poll_cb"). And in the callbacks of those requests, you can
587 group itself finish. 1272 add further requests to the group. And only when all those requests have
1273 finished will the the group itself finish.
588 1274
589 add $grp ... 1275 add $grp ...
590 $grp->add (...) 1276 $grp->add (...)
591 Add one or more requests to the group. Any type of IO::AIO::REQ can 1277 Add one or more requests to the group. Any type of IO::AIO::REQ can
592 be added, including other groups, as long as you do not create 1278 be added, including other groups, as long as you do not create
… …
597 $grp->cancel_subs 1283 $grp->cancel_subs
598 Cancel all subrequests and clears any feeder, but not the group 1284 Cancel all subrequests and clears any feeder, but not the group
599 request itself. Useful when you queued a lot of events but got a 1285 request itself. Useful when you queued a lot of events but got a
600 result early. 1286 result early.
601 1287
1288 The group request will finish normally (you cannot add requests to
1289 the group).
1290
602 $grp->result (...) 1291 $grp->result (...)
603 Set the result value(s) that will be passed to the group callback 1292 Set the result value(s) that will be passed to the group callback
604 when all subrequests have finished and set thre groups errno to the 1293 when all subrequests have finished and set the groups errno to the
605 current value of errno (just like calling "errno" without an error 1294 current value of errno (just like calling "errno" without an error
606 number). By default, no argument will be passed and errno is zero. 1295 number). By default, no argument will be passed and errno is zero.
607 1296
608 $grp->errno ([$errno]) 1297 $grp->errno ([$errno])
609 Sets the group errno value to $errno, or the current value of errno 1298 Sets the group errno value to $errno, or the current value of errno
… …
620 Sets a feeder/generator on this group: every group can have an 1309 Sets a feeder/generator on this group: every group can have an
621 attached generator that generates requests if idle. The idea behind 1310 attached generator that generates requests if idle. The idea behind
622 this is that, although you could just queue as many requests as you 1311 this is that, although you could just queue as many requests as you
623 want in a group, this might starve other requests for a potentially 1312 want in a group, this might starve other requests for a potentially
624 long time. For example, "aio_scandir" might generate hundreds of 1313 long time. For example, "aio_scandir" might generate hundreds of
625 thousands "aio_stat" requests, delaying any later requests for a 1314 thousands of "aio_stat" requests, delaying any later requests for a
626 long time. 1315 long time.
627 1316
628 To avoid this, and allow incremental generation of requests, you can 1317 To avoid this, and allow incremental generation of requests, you can
629 instead a group and set a feeder on it that generates those 1318 instead a group and set a feeder on it that generates those
630 requests. The feed callback will be called whenever there are few 1319 requests. The feed callback will be called whenever there are few
… …
635 does not impose any limits). 1324 does not impose any limits).
636 1325
637 If the feed does not queue more requests when called, it will be 1326 If the feed does not queue more requests when called, it will be
638 automatically removed from the group. 1327 automatically removed from the group.
639 1328
640 If the feed limit is 0, it will be set to 2 automatically. 1329 If the feed limit is 0 when this method is called, it will be set to
1330 2 automatically.
641 1331
642 Example: 1332 Example:
643 1333
644 # stat all files in @files, but only ever use four aio requests concurrently: 1334 # stat all files in @files, but only ever use four aio requests concurrently:
645 1335
… …
656 Sets the feeder limit for the group: The feeder will be called 1346 Sets the feeder limit for the group: The feeder will be called
657 whenever the group contains less than this many requests. 1347 whenever the group contains less than this many requests.
658 1348
659 Setting the limit to 0 will pause the feeding process. 1349 Setting the limit to 0 will pause the feeding process.
660 1350
1351 The default value for the limit is 0, but note that setting a feeder
1352 automatically bumps it up to 2.
1353
661 SUPPORT FUNCTIONS 1354 SUPPORT FUNCTIONS
662 EVENT PROCESSING AND EVENT LOOP INTEGRATION 1355 EVENT PROCESSING AND EVENT LOOP INTEGRATION
663 $fileno = IO::AIO::poll_fileno 1356 $fileno = IO::AIO::poll_fileno
664 Return the *request result pipe file descriptor*. This filehandle 1357 Return the *request result pipe file descriptor*. This filehandle
665 must be polled for reading by some mechanism outside this module 1358 must be polled for reading by some mechanism outside this module
666 (e.g. Event or select, see below or the SYNOPSIS). If the pipe 1359 (e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
667 becomes readable you have to call "poll_cb" to check the results. 1360 pipe becomes readable you have to call "poll_cb" to check the
1361 results.
668 1362
669 See "poll_cb" for an example. 1363 See "poll_cb" for an example.
670 1364
671 IO::AIO::poll_cb 1365 IO::AIO::poll_cb
672 Process some outstanding events on the result pipe. You have to call 1366 Process some requests that have reached the result phase (i.e. they
673 this regularly. Returns the number of events processed. Returns 1367 have been executed but the results are not yet reported). You have
1368 to call this "regularly" to finish outstanding requests.
1369
1370 Returns 0 if all events could be processed (or there were no events
1371 to process), or -1 if it returned earlier for whatever reason.
674 immediately when no events are outstanding. The amount of events 1372 Returns immediately when no events are outstanding. The amount of
675 processed depends on the settings of "IO::AIO::max_poll_req" and 1373 events processed depends on the settings of "IO::AIO::max_poll_req",
676 "IO::AIO::max_poll_time". 1374 "IO::AIO::max_poll_time" and "IO::AIO::max_outstanding".
677 1375
678 If not all requests were processed for whatever reason, the 1376 If not all requests were processed for whatever reason, the poll
679 filehandle will still be ready when "poll_cb" returns. 1377 file descriptor will still be ready when "poll_cb" returns, so
1378 normally you don't have to do anything special to have it called
1379 later.
1380
1381 Apart from calling "IO::AIO::poll_cb" when the event filehandle
1382 becomes ready, it can be beneficial to call this function from loops
1383 which submit a lot of requests, to make sure the results get
1384 processed when they become available and not just when the loop is
1385 finished and the event loop takes over again. This function returns
1386 very fast when there are no outstanding requests.
680 1387
681 Example: Install an Event watcher that automatically calls 1388 Example: Install an Event watcher that automatically calls
682 IO::AIO::poll_cb with high priority: 1389 IO::AIO::poll_cb with high priority (more examples can be found in
1390 the SYNOPSIS section, at the top of this document):
683 1391
684 Event->io (fd => IO::AIO::poll_fileno, 1392 Event->io (fd => IO::AIO::poll_fileno,
685 poll => 'r', async => 1, 1393 poll => 'r', async => 1,
686 cb => \&IO::AIO::poll_cb); 1394 cb => \&IO::AIO::poll_cb);
1395
1396 IO::AIO::poll_wait
1397 Wait until either at least one request is in the result phase or no
1398 requests are outstanding anymore.
1399
1400 This is useful if you want to synchronously wait for some requests
1401 to become ready, without actually handling them.
1402
1403 See "nreqs" for an example.
1404
1405 IO::AIO::poll
1406 Waits until some requests have been handled.
1407
1408 Returns the number of requests processed, but is otherwise strictly
1409 equivalent to:
1410
1411 IO::AIO::poll_wait, IO::AIO::poll_cb
1412
1413 IO::AIO::flush
1414 Wait till all outstanding AIO requests have been handled.
1415
1416 Strictly equivalent to:
1417
1418 IO::AIO::poll_wait, IO::AIO::poll_cb
1419 while IO::AIO::nreqs;
687 1420
688 IO::AIO::max_poll_reqs $nreqs 1421 IO::AIO::max_poll_reqs $nreqs
689 IO::AIO::max_poll_time $seconds 1422 IO::AIO::max_poll_time $seconds
690 These set the maximum number of requests (default 0, meaning 1423 These set the maximum number of requests (default 0, meaning
691 infinity) that are being processed by "IO::AIO::poll_cb" in one 1424 infinity) that are being processed by "IO::AIO::poll_cb" in one
… …
715 # use a low priority so other tasks have priority 1448 # use a low priority so other tasks have priority
716 Event->io (fd => IO::AIO::poll_fileno, 1449 Event->io (fd => IO::AIO::poll_fileno,
717 poll => 'r', nice => 1, 1450 poll => 'r', nice => 1,
718 cb => &IO::AIO::poll_cb); 1451 cb => &IO::AIO::poll_cb);
719 1452
720 IO::AIO::poll_wait
721 If there are any outstanding requests and none of them in the result
722 phase, wait till the result filehandle becomes ready for reading
723 (simply does a "select" on the filehandle. This is useful if you
724 want to synchronously wait for some requests to finish).
725
726 See "nreqs" for an example.
727
728 IO::AIO::poll
729 Waits until some requests have been handled.
730
731 Returns the number of requests processed, but is otherwise strictly
732 equivalent to:
733
734 IO::AIO::poll_wait, IO::AIO::poll_cb
735
736 IO::AIO::flush
737 Wait till all outstanding AIO requests have been handled.
738
739 Strictly equivalent to:
740
741 IO::AIO::poll_wait, IO::AIO::poll_cb
742 while IO::AIO::nreqs;
743
744 CONTROLLING THE NUMBER OF THREADS 1453 CONTROLLING THE NUMBER OF THREADS
745 IO::AIO::min_parallel $nthreads 1454 IO::AIO::min_parallel $nthreads
746 Set the minimum number of AIO threads to $nthreads. The current 1455 Set the minimum number of AIO threads to $nthreads. The current
747 default is 8, which means eight asynchronous operations can execute 1456 default is 8, which means eight asynchronous operations can execute
748 concurrently at any one time (the number of outstanding requests, 1457 concurrently at any one time (the number of outstanding requests,
… …
777 1486
778 Under normal circumstances you don't need to call this function. 1487 Under normal circumstances you don't need to call this function.
779 1488
780 IO::AIO::max_idle $nthreads 1489 IO::AIO::max_idle $nthreads
781 Limit the number of threads (default: 4) that are allowed to idle 1490 Limit the number of threads (default: 4) that are allowed to idle
782 (i.e., threads that did not get a request to process within 10 1491 (i.e., threads that did not get a request to process within the idle
783 seconds). That means if a thread becomes idle while $nthreads other 1492 timeout (default: 10 seconds). That means if a thread becomes idle
784 threads are also idle, it will free its resources and exit. 1493 while $nthreads other threads are also idle, it will free its
1494 resources and exit.
785 1495
786 This is useful when you allow a large number of threads (e.g. 100 or 1496 This is useful when you allow a large number of threads (e.g. 100 or
787 1000) to allow for extremely high load situations, but want to free 1497 1000) to allow for extremely high load situations, but want to free
788 resources under normal circumstances (1000 threads can easily 1498 resources under normal circumstances (1000 threads can easily
789 consume 30MB of RAM). 1499 consume 30MB of RAM).
790 1500
791 The default is probably ok in most situations, especially if thread 1501 The default is probably ok in most situations, especially if thread
792 creation is fast. If thread creation is very slow on your system you 1502 creation is fast. If thread creation is very slow on your system you
793 might want to use larger values. 1503 might want to use larger values.
794 1504
1505 IO::AIO::idle_timeout $seconds
1506 Sets the minimum idle timeout (default 10) after which worker
1507 threads are allowed to exit. SEe "IO::AIO::max_idle".
1508
795 $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1509 IO::AIO::max_outstanding $maxreqs
1510 Sets the maximum number of outstanding requests to $nreqs. If you do
1511 queue up more than this number of requests, the next call to
1512 "IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
1513 "IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
1514 no longer exceeded.
1515
1516 In other words, this setting does not enforce a queue limit, but can
1517 be used to make poll functions block if the limit is exceeded.
1518
796 This is a very bad function to use in interactive programs because 1519 This is a very bad function to use in interactive programs because
797 it blocks, and a bad way to reduce concurrency because it is 1520 it blocks, and a bad way to reduce concurrency because it is
798 inexact: Better use an "aio_group" together with a feed callback. 1521 inexact: Better use an "aio_group" together with a feed callback.
799 1522
800 Sets the maximum number of outstanding requests to $nreqs. If you to 1523 It's main use is in scripts without an event loop - when you want to
801 queue up more than this number of requests, the next call to the 1524 stat a lot of files, you can write somehting like this:
802 "poll_cb" (and "poll_some" and other functions calling "poll_cb")
803 function will block until the limit is no longer exceeded.
804 1525
805 The default value is very large, so there is no practical limit on 1526 IO::AIO::max_outstanding 32;
1527
1528 for my $path (...) {
1529 aio_stat $path , ...;
1530 IO::AIO::poll_cb;
1531 }
1532
1533 IO::AIO::flush;
1534
1535 The call to "poll_cb" inside the loop will normally return
1536 instantly, but as soon as more thna 32 reqeusts are in-flight, it
1537 will block until some requests have been handled. This keeps the
1538 loop from pushing a large number of "aio_stat" requests onto the
1539 queue.
1540
1541 The default value for "max_outstanding" is very large, so there is
806 the number of outstanding requests. 1542 no practical limit on the number of outstanding requests.
807
808 You can still queue as many requests as you want. Therefore,
809 "max_oustsanding" is mainly useful in simple scripts (with low
810 values) or as a stop gap to shield against fatal memory overflow
811 (with large values).
812 1543
813 STATISTICAL INFORMATION 1544 STATISTICAL INFORMATION
814 IO::AIO::nreqs 1545 IO::AIO::nreqs
815 Returns the number of requests currently in the ready, execute or 1546 Returns the number of requests currently in the ready, execute or
816 pending states (i.e. for which their callback has not been invoked 1547 pending states (i.e. for which their callback has not been invoked
… …
827 1558
828 IO::AIO::npending 1559 IO::AIO::npending
829 Returns the number of requests currently in the pending state 1560 Returns the number of requests currently in the pending state
830 (executed, but not yet processed by poll_cb). 1561 (executed, but not yet processed by poll_cb).
831 1562
1563 MISCELLANEOUS FUNCTIONS
1564 IO::AIO implements some functions that might be useful, but are not
1565 asynchronous.
1566
1567 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1568 Calls the "eio_sendfile_sync" function, which is like
1569 "aio_sendfile", but is blocking (this makes most sense if you know
1570 the input data is likely cached already and the output filehandle is
1571 set to non-blocking operations).
1572
1573 Returns the number of bytes copied, or -1 on error.
1574
1575 IO::AIO::fadvise $fh, $offset, $len, $advice
1576 Simply calls the "posix_fadvise" function (see its manpage for
1577 details). The following advice constants are available:
1578 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1579 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1580 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1581
1582 On systems that do not implement "posix_fadvise", this function
1583 returns ENOSYS, otherwise the return value of "posix_fadvise".
1584
1585 IO::AIO::madvise $scalar, $offset, $len, $advice
1586 Simply calls the "posix_madvise" function (see its manpage for
1587 details). The following advice constants are available:
1588 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1589 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1590 "IO::AIO::MADV_DONTNEED".
1591
1592 On systems that do not implement "posix_madvise", this function
1593 returns ENOSYS, otherwise the return value of "posix_madvise".
1594
1595 IO::AIO::mprotect $scalar, $offset, $len, $protect
1596 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1597 $scalar (see its manpage for details). The following protect
1598 constants are available: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1599 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1600
1601 On systems that do not implement "mprotect", this function returns
1602 ENOSYS, otherwise the return value of "mprotect".
1603
1604 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1605 Memory-maps a file (or anonymous memory range) and attaches it to
1606 the given $scalar, which will act like a string scalar. Returns true
1607 on success, and false otherwise.
1608
1609 The only operations allowed on the scalar are "substr"/"vec" that
1610 don't change the string length, and most read-only operations such
1611 as copying it or searching it with regexes and so on.
1612
1613 Anything else is unsafe and will, at best, result in memory leaks.
1614
1615 The memory map associated with the $scalar is automatically removed
1616 when the $scalar is destroyed, or when the "IO::AIO::mmap" or
1617 "IO::AIO::munmap" functions are called.
1618
1619 This calls the "mmap"(2) function internally. See your system's
1620 manual page for details on the $length, $prot and $flags parameters.
1621
1622 The $length must be larger than zero and smaller than the actual
1623 filesize.
1624
1625 $prot is a combination of "IO::AIO::PROT_NONE",
1626 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1627 "IO::AIO::PROT_WRITE",
1628
1629 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1630 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1631 not available, the are defined as 0): "IO::AIO::MAP_ANONYMOUS"
1632 (which is set to "MAP_ANON" if your system only provides this
1633 constant), "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED",
1634 "IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or
1635 "IO::AIO::MAP_NONBLOCK"
1636
1637 If $fh is "undef", then a file descriptor of -1 is passed.
1638
1639 $offset is the offset from the start of the file - it generally must
1640 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
1641
1642 Example:
1643
1644 use Digest::MD5;
1645 use IO::AIO;
1646
1647 open my $fh, "<verybigfile"
1648 or die "$!";
1649
1650 IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
1651 or die "verybigfile: $!";
1652
1653 my $fast_md5 = md5 $data;
1654
1655 IO::AIO::munmap $scalar
1656 Removes a previous mmap and undefines the $scalar.
1657
1658 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1659 Calls the "munlock" function, undoing the effects of a previous
1660 "aio_mlock" call (see its description for details).
1661
1662 IO::AIO::munlockall
1663 Calls the "munlockall" function.
1664
1665 On systems that do not implement "munlockall", this function returns
1666 ENOSYS, otherwise the return value of "munlockall".
1667
1668 IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
1669 Calls the GNU/Linux splice(2) syscall, if available. If $r_off or
1670 $w_off are "undef", then "NULL" is passed for these, otherwise they
1671 should be the file offset.
1672
1673 $r_fh and $w_fh should not refer to the same file, as splice might
1674 silently corrupt the data in this case.
1675
1676 The following symbol flag values are available:
1677 "IO::AIO::SPLICE_F_MOVE", "IO::AIO::SPLICE_F_NONBLOCK",
1678 "IO::AIO::SPLICE_F_MORE" and "IO::AIO::SPLICE_F_GIFT".
1679
1680 See the splice(2) manpage for details.
1681
1682 IO::AIO::tee $r_fh, $w_fh, $length, $flags
1683 Calls the GNU/Linux tee(2) syscall, see it's manpage and the
1684 description for "IO::AIO::splice" above for details.
1685
1686 $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
1687 Attempts to query or change the pipe buffer size. Obviously works
1688 only on pipes, and currently works only on GNU/Linux systems, and
1689 fails with -1/"ENOSYS" everywhere else. If anybody knows how to
1690 influence pipe buffer size on other systems, drop me a note.
1691
1692EVENT LOOP INTEGRATION
1693 It is recommended to use AnyEvent::AIO to integrate IO::AIO
1694 automatically into many event loops:
1695
1696 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
1697 use AnyEvent::AIO;
1698
1699 You can also integrate IO::AIO manually into many event loops, here are
1700 some examples of how to do this:
1701
1702 # EV integration
1703 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
1704
1705 # Event integration
1706 Event->io (fd => IO::AIO::poll_fileno,
1707 poll => 'r',
1708 cb => \&IO::AIO::poll_cb);
1709
1710 # Glib/Gtk2 integration
1711 add_watch Glib::IO IO::AIO::poll_fileno,
1712 in => sub { IO::AIO::poll_cb; 1 };
1713
1714 # Tk integration
1715 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
1716 readable => \&IO::AIO::poll_cb);
1717
1718 # Danga::Socket integration
1719 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1720 \&IO::AIO::poll_cb);
1721
832 FORK BEHAVIOUR 1722 FORK BEHAVIOUR
833 This module should do "the right thing" when the process using it forks: 1723 Usage of pthreads in a program changes the semantics of fork
1724 considerably. Specifically, only async-safe functions can be called
1725 after fork. Perl doesn't know about this, so in general, you cannot call
1726 fork with defined behaviour in perl if pthreads are involved. IO::AIO
1727 uses pthreads, so this applies, but many other extensions and (for
1728 inexplicable reasons) perl itself often is linked against pthreads, so
1729 this limitation applies to quite a lot of perls.
834 1730
835 Before the fork, IO::AIO enters a quiescent state where no requests can 1731 This module no longer tries to fight your OS, or POSIX. That means
836 be added in other threads and no results will be processed. After the 1732 IO::AIO only works in the process that loaded it. Forking is fully
837 fork the parent simply leaves the quiescent state and continues 1733 supported, but using IO::AIO in the child is not.
838 request/result processing, while the child frees the request/result
839 queue (so that the requests started before the fork will only be handled
840 in the parent). Threads will be started on demand until the limit set in
841 the parent process has been reached again.
842 1734
843 In short: the parent will, after a short pause, continue as if fork had 1735 You might get around by not *using* IO::AIO before (or after) forking.
844 not been called, while the child will act as if IO::AIO has not been 1736 You could also try to call the IO::AIO::reinit function in the child:
845 used yet. 1737
1738 IO::AIO::reinit
1739 Abandons all current requests and I/O threads and simply
1740 reinitialises all data structures. This is not an operation
1741 supported by any standards, but happens to work on GNU/Linux and
1742 some newer BSD systems.
1743
1744 The only reasonable use for this function is to call it after
1745 forking, if "IO::AIO" was used in the parent. Calling it while
1746 IO::AIO is active in the process will result in undefined behaviour.
1747 Calling it at any time will also result in any undefined (by POSIX)
1748 behaviour.
846 1749
847 MEMORY USAGE 1750 MEMORY USAGE
848 Per-request usage: 1751 Per-request usage:
849 1752
850 Each aio request uses - depending on your architecture - around 100-200 1753 Each aio request uses - depending on your architecture - around 100-200
851 bytes of memory. In addition, stat requests need a stat buffer (possibly 1754 bytes of memory. In addition, stat requests need a stat buffer (possibly
852 a few hundred bytes), readdir requires a result buffer and so on. Perl 1755 a few hundred bytes), readdir requires a result buffer and so on. Perl
853 scalars and other data passed into aio requests will also be locked and 1756 scalars and other data passed into aio requests will also be locked and
854 will consume memory till the request has entered the done state. 1757 will consume memory till the request has entered the done state.
855 1758
856 This is now awfully much, so queuing lots of requests is not usually a 1759 This is not awfully much, so queuing lots of requests is not usually a
857 problem. 1760 problem.
858 1761
859 Per-thread usage: 1762 Per-thread usage:
860 1763
861 In the execution phase, some aio requests require more memory for 1764 In the execution phase, some aio requests require more memory for
… …
864 1767
865KNOWN BUGS 1768KNOWN BUGS
866 Known bugs will be fixed in the next release. 1769 Known bugs will be fixed in the next release.
867 1770
868SEE ALSO 1771SEE ALSO
869 Coro::AIO. 1772 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
1773 more natural syntax.
870 1774
871AUTHOR 1775AUTHOR
872 Marc Lehmann <schmorp@schmorp.de> 1776 Marc Lehmann <schmorp@schmorp.de>
873 http://home.schmorp.de/ 1777 http://home.schmorp.de/
874 1778

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