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Revision 1.49 by root, Mon Jul 18 03:09:06 2011 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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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 Use an event loop for that (such as the Event module): IO::AIO will 47 Use an event loop for that (such as the EV module): IO::AIO will
68 naturally fit into such an event loop itself. 48 naturally fit into such an event loop itself.
69 49
70 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
71 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
72 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
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81 it is currently not reentrant in any way, so use appropriate locking 61 it is currently not reentrant in any way, so use appropriate locking
82 yourself, always call "poll_cb" from within the same thread, or never 62 yourself, always call "poll_cb" from within the same thread, or never
83 call "poll_cb" (or other "aio_" functions) recursively. 63 call "poll_cb" (or other "aio_" functions) recursively.
84 64
85 EXAMPLE 65 EXAMPLE
86 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
87 /etc/passwd asynchronously: 67 asynchronously:
88 68
89 use Fcntl; 69 use Fcntl;
90 use Event; 70 use EV;
91 use IO::AIO; 71 use IO::AIO;
92 72
93 # register the IO::AIO callback with Event 73 # register the IO::AIO callback with EV
94 Event->io (fd => IO::AIO::poll_fileno, 74 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
95 poll => 'r',
96 cb => \&IO::AIO::poll_cb);
97 75
98 # queue the request to open /etc/passwd 76 # queue the request to open /etc/passwd
99 aio_open "/etc/passwd", O_RDONLY, 0, sub { 77 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
100 my $fh = shift 78 my $fh = shift
101 or die "error while opening: $!"; 79 or die "error while opening: $!";
102 80
103 # stat'ing filehandles is generally non-blocking 81 # stat'ing filehandles is generally non-blocking
104 my $size = -s $fh; 82 my $size = -s $fh;
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113 91
114 # file contents now in $contents 92 # file contents now in $contents
115 print $contents; 93 print $contents;
116 94
117 # exit event loop and program 95 # exit event loop and program
118 Event::unloop; 96 EV::unloop;
119 }; 97 };
120 }; 98 };
121 99
122 # possibly queue up other requests, or open GUI windows, 100 # possibly queue up other requests, or open GUI windows,
123 # check for sockets etc. etc. 101 # check for sockets etc. etc.
124 102
125 # process events as long as there are some: 103 # process events as long as there are some:
126 Event::loop; 104 EV::loop;
127 105
128REQUEST ANATOMY AND LIFETIME 106REQUEST ANATOMY AND LIFETIME
129 Every "aio_*" function creates a request. which is a C data structure 107 Every "aio_*" function creates a request. which is a C data structure
130 not directly visible to Perl. 108 not directly visible to Perl.
131 109
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167 anymore (except possibly for the Perl object, but its connection to 145 anymore (except possibly for the Perl object, but its connection to
168 the actual aio request is severed and calling its methods will 146 the actual aio request is severed and calling its methods will
169 either do nothing or result in a runtime error). 147 either do nothing or result in a runtime error).
170 148
171FUNCTIONS 149FUNCTIONS
150 QUICK OVERVIEW
151 This section simply lists the prototypes of the most important functions
152 for quick reference. See the following sections for function-by-function
153 documentation.
154
155 aio_open $pathname, $flags, $mode, $callback->($fh)
156 aio_close $fh, $callback->($status)
157 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
158 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
159 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
160 aio_readahead $fh,$offset,$length, $callback->($retval)
161 aio_stat $fh_or_path, $callback->($status)
162 aio_lstat $fh, $callback->($status)
163 aio_statvfs $fh_or_path, $callback->($statvfs)
164 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
165 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
166 aio_truncate $fh_or_path, $offset, $callback->($status)
167 aio_chmod $fh_or_path, $mode, $callback->($status)
168 aio_unlink $pathname, $callback->($status)
169 aio_mknod $path, $mode, $dev, $callback->($status)
170 aio_link $srcpath, $dstpath, $callback->($status)
171 aio_symlink $srcpath, $dstpath, $callback->($status)
172 aio_readlink $path, $callback->($link)
173 aio_realpath $path, $callback->($link)
174 aio_rename $srcpath, $dstpath, $callback->($status)
175 aio_mkdir $pathname, $mode, $callback->($status)
176 aio_rmdir $pathname, $callback->($status)
177 aio_readdir $pathname, $callback->($entries)
178 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
179 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
180 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
181 aio_load $path, $data, $callback->($status)
182 aio_copy $srcpath, $dstpath, $callback->($status)
183 aio_move $srcpath, $dstpath, $callback->($status)
184 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
185 aio_rmtree $path, $callback->($status)
186 aio_sync $callback->($status)
187 aio_fsync $fh, $callback->($status)
188 aio_fdatasync $fh, $callback->($status)
189 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
190 aio_pathsync $path, $callback->($status)
191 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
192 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
193 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
194 aio_mlockall $flags, $callback->($status)
195 aio_group $callback->(...)
196 aio_nop $callback->()
197
198 $prev_pri = aioreq_pri [$pri]
199 aioreq_nice $pri_adjust
200
201 IO::AIO::poll_wait
202 IO::AIO::poll_cb
203 IO::AIO::poll
204 IO::AIO::flush
205 IO::AIO::max_poll_reqs $nreqs
206 IO::AIO::max_poll_time $seconds
207 IO::AIO::min_parallel $nthreads
208 IO::AIO::max_parallel $nthreads
209 IO::AIO::max_idle $nthreads
210 IO::AIO::idle_timeout $seconds
211 IO::AIO::max_outstanding $maxreqs
212 IO::AIO::nreqs
213 IO::AIO::nready
214 IO::AIO::npending
215
216 IO::AIO::sendfile $ofh, $ifh, $offset, $count
217 IO::AIO::fadvise $fh, $offset, $len, $advice
218 IO::AIO::madvise $scalar, $offset, $length, $advice
219 IO::AIO::mprotect $scalar, $offset, $length, $protect
220 IO::AIO::munlock $scalar, $offset = 0, $length = undef
221 IO::AIO::munlockall
222
172 AIO REQUEST FUNCTIONS 223 AIO REQUEST FUNCTIONS
173 All the "aio_*" calls are more or less thin wrappers around the syscall 224 All the "aio_*" calls are more or less thin wrappers around the syscall
174 with the same name (sans "aio_"). The arguments are similar or 225 with the same name (sans "aio_"). The arguments are similar or
175 identical, and they all accept an additional (and optional) $callback 226 identical, and they all accept an additional (and optional) $callback
176 argument which must be a code reference. This code reference will get 227 argument which must be a code reference. This code reference will get
177 called with the syscall return code (e.g. most syscalls return -1 on 228 called with the syscall return code (e.g. most syscalls return -1 on
178 error, unlike perl, which usually delivers "false") as it's sole 229 error, unlike perl, which usually delivers "false") as its sole argument
179 argument when the given syscall has been executed asynchronously. 230 after the given syscall has been executed asynchronously.
180 231
181 All functions expecting a filehandle keep a copy of the filehandle 232 All functions expecting a filehandle keep a copy of the filehandle
182 internally until the request has finished. 233 internally until the request has finished.
183 234
184 All functions return request objects of type IO::AIO::REQ that allow 235 All functions return request objects of type IO::AIO::REQ that allow
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197 the user environment, d) use Glib::filename_from_unicode on unicode 248 the user environment, d) use Glib::filename_from_unicode on unicode
198 filenames or e) use something else to ensure your scalar has the correct 249 filenames or e) use something else to ensure your scalar has the correct
199 contents. 250 contents.
200 251
201 This works, btw. independent of the internal UTF-8 bit, which IO::AIO 252 This works, btw. independent of the internal UTF-8 bit, which IO::AIO
202 handles correctly wether it is set or not. 253 handles correctly whether it is set or not.
203 254
204 $prev_pri = aioreq_pri [$pri] 255 $prev_pri = aioreq_pri [$pri]
205 Returns the priority value that would be used for the next request 256 Returns the priority value that would be used for the next request
206 and, if $pri is given, sets the priority for the next aio request. 257 and, if $pri is given, sets the priority for the next aio request.
207 258
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247 will be modified by the umask in effect then the request is being 298 will be modified by the umask in effect then the request is being
248 executed, so better never change the umask. 299 executed, so better never change the umask.
249 300
250 Example: 301 Example:
251 302
252 aio_open "/etc/passwd", O_RDONLY, 0, sub { 303 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
253 if ($_[0]) { 304 if ($_[0]) {
254 print "open successful, fh is $_[0]\n"; 305 print "open successful, fh is $_[0]\n";
255 ... 306 ...
256 } else { 307 } else {
257 die "open failed: $!\n"; 308 die "open failed: $!\n";
258 } 309 }
259 }; 310 };
260 311
312 In addition to all the common open modes/flags ("O_RDONLY",
313 "O_WRONLY", "O_RDWR", "O_CREAT", "O_TRUNC", "O_EXCL" and
314 "O_APPEND"), the following POSIX and non-POSIX constants are
315 available (missing ones on your system are, as usual, 0):
316
317 "O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",
318 "O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",
319 "O_DSYNC", "O_RSYNC", "O_SYNC" and "O_TTY_INIT".
320
261 aio_close $fh, $callback->($status) 321 aio_close $fh, $callback->($status)
262 Asynchronously close a file and call the callback with the result 322 Asynchronously close a file and call the callback with the result
263 code. *WARNING:* although accepted, you should not pass in a perl 323 code.
264 filehandle here, as perl will likely close the file descriptor
265 another time when the filehandle is destroyed. Normally, you can
266 safely call perls "close" or just let filehandles go out of scope.
267 324
268 This is supposed to be a bug in the API, so that might change. It's 325 Unfortunately, you can't do this to perl. Perl *insists* very
269 therefore best to avoid this function. 326 strongly on closing the file descriptor associated with the
327 filehandle itself.
328
329 Therefore, "aio_close" will not close the filehandle - instead it
330 will use dup2 to overwrite the file descriptor with the write-end of
331 a pipe (the pipe fd will be created on demand and will be cached).
332
333 Or in other words: the file descriptor will be closed, but it will
334 not be free for reuse until the perl filehandle is closed.
270 335
271 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 336 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
272 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 337 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
273 Reads or writes $length bytes from the specified $fh and $offset 338 Reads or writes $length bytes from or to the specified $fh and
274 into the scalar given by $data and offset $dataoffset and calls the 339 $offset into the scalar given by $data and offset $dataoffset and
275 callback without the actual number of bytes read (or -1 on error, 340 calls the callback without the actual number of bytes read (or -1 on
276 just like the syscall). 341 error, just like the syscall).
342
343 "aio_read" will, like "sysread", shrink or grow the $data scalar to
344 offset plus the actual number of bytes read.
277 345
278 If $offset is undefined, then the current file descriptor offset 346 If $offset is undefined, then the current file descriptor offset
279 will be used (and updated), otherwise the file descriptor offset 347 will be used (and updated), otherwise the file descriptor offset
280 will not be changed by these calls. 348 will not be changed by these calls.
281 349
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300 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 368 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
301 Tries to copy $length bytes from $in_fh to $out_fh. It starts 369 Tries to copy $length bytes from $in_fh to $out_fh. It starts
302 reading at byte offset $in_offset, and starts writing at the current 370 reading at byte offset $in_offset, and starts writing at the current
303 file offset of $out_fh. Because of that, it is not safe to issue 371 file offset of $out_fh. Because of that, it is not safe to issue
304 more than one "aio_sendfile" per $out_fh, as they will interfere 372 more than one "aio_sendfile" per $out_fh, as they will interfere
305 with each other. 373 with each other. The same $in_fh works fine though, as this function
374 does not move or use the file offset of $in_fh.
306 375
376 Please note that "aio_sendfile" can read more bytes from $in_fh than
377 are written, and there is no way to find out how many more bytes
378 have been read from "aio_sendfile" alone, as "aio_sendfile" only
379 provides the number of bytes written to $out_fh. Only if the result
380 value equals $length one can assume that $length bytes have been
381 read.
382
383 Unlike with other "aio_" functions, it makes a lot of sense to use
384 "aio_sendfile" on non-blocking sockets, as long as one end
385 (typically the $in_fh) is a file - the file I/O will then be
386 asynchronous, while the socket I/O will be non-blocking. Note,
387 however, that you can run into a trap where "aio_sendfile" reads
388 some data with readahead, then fails to write all data, and when the
389 socket is ready the next time, the data in the cache is already
390 lost, forcing "aio_sendfile" to again hit the disk. Explicit
391 "aio_read" + "aio_write" let's you better control resource usage.
392
307 This call tries to make use of a native "sendfile" syscall to 393 This call tries to make use of a native "sendfile"-like syscall to
308 provide zero-copy operation. For this to work, $out_fh should refer 394 provide zero-copy operation. For this to work, $out_fh should refer
309 to a socket, and $in_fh should refer to mmap'able file. 395 to a socket, and $in_fh should refer to an mmap'able file.
310 396
311 If the native sendfile call fails or is not implemented, it will be 397 If a native sendfile cannot be found or it fails with "ENOSYS",
312 emulated, so you can call "aio_sendfile" on any type of filehandle 398 "EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
313 regardless of the limitations of the operating system. 399 "ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on
400 any type of filehandle regardless of the limitations of the
401 operating system.
314 402
315 Please note, however, that "aio_sendfile" can read more bytes from 403 As native sendfile syscalls (as practically any non-POSIX interface
316 $in_fh than are written, and there is no way to find out how many 404 hacked together in a hurry to improve benchmark numbers) tend to be
317 bytes have been read from "aio_sendfile" alone, as "aio_sendfile" 405 rather buggy on many systems, this implementation tries to work
318 only provides the number of bytes written to $out_fh. Only if the 406 around some known bugs in Linux and FreeBSD kernels (probably
319 result value equals $length one can assume that $length bytes have 407 others, too), but that might fail, so you really really should check
320 been read. 408 the return value of "aio_sendfile" - fewre bytes than expected might
409 have been transferred.
321 410
322 aio_readahead $fh,$offset,$length, $callback->($retval) 411 aio_readahead $fh,$offset,$length, $callback->($retval)
323 "aio_readahead" populates the page cache with data from a file so 412 "aio_readahead" populates the page cache with data from a file so
324 that subsequent reads from that file will not block on disk I/O. The 413 that subsequent reads from that file will not block on disk I/O. The
325 $offset argument specifies the starting point from which data is to 414 $offset argument specifies the starting point from which data is to
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346 Currently, the stats are always 64-bit-stats, i.e. instead of 435 Currently, the stats are always 64-bit-stats, i.e. instead of
347 returning an error when stat'ing a large file, the results will be 436 returning an error when stat'ing a large file, the results will be
348 silently truncated unless perl itself is compiled with large file 437 silently truncated unless perl itself is compiled with large file
349 support. 438 support.
350 439
440 To help interpret the mode and dev/rdev stat values, IO::AIO offers
441 the following constants and functions (if not implemented, the
442 constants will be 0 and the functions will either "croak" or fall
443 back on traditional behaviour).
444
445 "S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
446 "S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
447 "IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
448
351 Example: Print the length of /etc/passwd: 449 Example: Print the length of /etc/passwd:
352 450
353 aio_stat "/etc/passwd", sub { 451 aio_stat "/etc/passwd", sub {
354 $_[0] and die "stat failed: $!"; 452 $_[0] and die "stat failed: $!";
355 print "size is ", -s _, "\n"; 453 print "size is ", -s _, "\n";
356 }; 454 };
357 455
456 aio_statvfs $fh_or_path, $callback->($statvfs)
457 Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
458 whether a file handle or path was passed.
459
460 On success, the callback is passed a hash reference with the
461 following members: "bsize", "frsize", "blocks", "bfree", "bavail",
462 "files", "ffree", "favail", "fsid", "flag" and "namemax". On
463 failure, "undef" is passed.
464
465 The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
466 and "ST_NOSUID".
467
468 The following non-POSIX IO::AIO::ST_* flag masks are defined to
469 their correct value when available, or to 0 on systems that do not
470 support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
471 "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
472 "ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
473
474 Example: stat "/wd" and dump out the data if successful.
475
476 aio_statvfs "/wd", sub {
477 my $f = $_[0]
478 or die "statvfs: $!";
479
480 use Data::Dumper;
481 say Dumper $f;
482 };
483
484 # result:
485 {
486 bsize => 1024,
487 bfree => 4333064312,
488 blocks => 10253828096,
489 files => 2050765568,
490 flag => 4096,
491 favail => 2042092649,
492 bavail => 4333064312,
493 ffree => 2042092649,
494 namemax => 255,
495 frsize => 1024,
496 fsid => 1810
497 }
498
358 aio_utime $fh_or_path, $atime, $mtime, $callback->($status) 499 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
359 Works like perl's "utime" function (including the special case of 500 Works like perl's "utime" function (including the special case of
360 $atime and $mtime being undef). Fractional times are supported if 501 $atime and $mtime being undef). Fractional times are supported if
361 the underlying syscalls support them. 502 the underlying syscalls support them.
362 503
… …
400 541
401 The only (POSIX-) portable way of calling this function is: 542 The only (POSIX-) portable way of calling this function is:
402 543
403 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... 544 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
404 545
546 See "aio_stat" for info about some potentially helpful extra
547 constants and functions.
548
405 aio_link $srcpath, $dstpath, $callback->($status) 549 aio_link $srcpath, $dstpath, $callback->($status)
406 Asynchronously create a new link to the existing object at $srcpath 550 Asynchronously create a new link to the existing object at $srcpath
407 at the path $dstpath and call the callback with the result code. 551 at the path $dstpath and call the callback with the result code.
408 552
409 aio_symlink $srcpath, $dstpath, $callback->($status) 553 aio_symlink $srcpath, $dstpath, $callback->($status)
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414 aio_readlink $path, $callback->($link) 558 aio_readlink $path, $callback->($link)
415 Asynchronously read the symlink specified by $path and pass it to 559 Asynchronously read the symlink specified by $path and pass it to
416 the callback. If an error occurs, nothing or undef gets passed to 560 the callback. If an error occurs, nothing or undef gets passed to
417 the callback. 561 the callback.
418 562
563 aio_realpath $path, $callback->($path)
564 Asynchronously make the path absolute and resolve any symlinks in
565 $path. The resulting path only consists of directories (Same as
566 Cwd::realpath).
567
568 This request can be used to get the absolute path of the current
569 working directory by passing it a path of . (a single dot).
570
419 aio_rename $srcpath, $dstpath, $callback->($status) 571 aio_rename $srcpath, $dstpath, $callback->($status)
420 Asynchronously rename the object at $srcpath to $dstpath, just as 572 Asynchronously rename the object at $srcpath to $dstpath, just as
421 rename(2) and call the callback with the result code. 573 rename(2) and call the callback with the result code.
422 574
423 aio_mkdir $pathname, $mode, $callback->($status) 575 aio_mkdir $pathname, $mode, $callback->($status)
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432 aio_readdir $pathname, $callback->($entries) 584 aio_readdir $pathname, $callback->($entries)
433 Unlike the POSIX call of the same name, "aio_readdir" reads an 585 Unlike the POSIX call of the same name, "aio_readdir" reads an
434 entire directory (i.e. opendir + readdir + closedir). The entries 586 entire directory (i.e. opendir + readdir + closedir). The entries
435 will not be sorted, and will NOT include the "." and ".." entries. 587 will not be sorted, and will NOT include the "." and ".." entries.
436 588
437 The callback a single argument which is either "undef" or an 589 The callback is passed a single argument which is either "undef" or
438 array-ref with the filenames. 590 an array-ref with the filenames.
591
592 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
593 Quite similar to "aio_readdir", but the $flags argument allows to
594 tune behaviour and output format. In case of an error, $entries will
595 be "undef".
596
597 The flags are a combination of the following constants, ORed
598 together (the flags will also be passed to the callback, possibly
599 modified):
600
601 IO::AIO::READDIR_DENTS
602 When this flag is off, then the callback gets an arrayref
603 consisting of names only (as with "aio_readdir"), otherwise it
604 gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
605 describing a single directory entry in more detail.
606
607 $name is the name of the entry.
608
609 $type is one of the "IO::AIO::DT_xxx" constants:
610
611 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
612 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
613 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
614
615 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
616 you need to know, you have to run stat yourself. Also, for speed
617 reasons, the $type scalars are read-only: you can not modify
618 them.
619
620 $inode is the inode number (which might not be exact on systems
621 with 64 bit inode numbers and 32 bit perls). This field has
622 unspecified content on systems that do not deliver the inode
623 information.
624
625 IO::AIO::READDIR_DIRS_FIRST
626 When this flag is set, then the names will be returned in an
627 order where likely directories come first, in optimal stat
628 order. This is useful when you need to quickly find directories,
629 or you want to find all directories while avoiding to stat()
630 each entry.
631
632 If the system returns type information in readdir, then this is
633 used to find directories directly. Otherwise, likely directories
634 are names beginning with ".", or otherwise names with no dots,
635 of which names with short names are tried first.
636
637 IO::AIO::READDIR_STAT_ORDER
638 When this flag is set, then the names will be returned in an
639 order suitable for stat()'ing each one. That is, when you plan
640 to stat() all files in the given directory, then the returned
641 order will likely be fastest.
642
643 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
644 specified, then the likely dirs come first, resulting in a less
645 optimal stat order.
646
647 IO::AIO::READDIR_FOUND_UNKNOWN
648 This flag should not be set when calling "aio_readdirx".
649 Instead, it is being set by "aio_readdirx", when any of the
650 $type's found were "IO::AIO::DT_UNKNOWN". The absense of this
651 flag therefore indicates that all $type's are known, which can
652 be used to speed up some algorithms.
439 653
440 aio_load $path, $data, $callback->($status) 654 aio_load $path, $data, $callback->($status)
441 This is a composite request that tries to fully load the given file 655 This is a composite request that tries to fully load the given file
442 into memory. Status is the same as with aio_read. 656 into memory. Status is the same as with aio_read.
443 657
444 aio_copy $srcpath, $dstpath, $callback->($status) 658 aio_copy $srcpath, $dstpath, $callback->($status)
445 Try to copy the *file* (directories not supported as either source 659 Try to copy the *file* (directories not supported as either source
446 or destination) from $srcpath to $dstpath and call the callback with 660 or destination) from $srcpath to $dstpath and call the callback with
447 the 0 (error) or -1 ok. 661 a status of 0 (ok) or -1 (error, see $!).
448 662
449 This is a composite request that it creates the destination file 663 This is a composite request that creates the destination file with
450 with mode 0200 and copies the contents of the source file into it 664 mode 0200 and copies the contents of the source file into it using
451 using "aio_sendfile", followed by restoring atime, mtime, access 665 "aio_sendfile", followed by restoring atime, mtime, access mode and
452 mode and uid/gid, in that order. 666 uid/gid, in that order.
453 667
454 If an error occurs, the partial destination file will be unlinked, 668 If an error occurs, the partial destination file will be unlinked,
455 if possible, except when setting atime, mtime, access mode and 669 if possible, except when setting atime, mtime, access mode and
456 uid/gid, where errors are being ignored. 670 uid/gid, where errors are being ignored.
457 671
458 aio_move $srcpath, $dstpath, $callback->($status) 672 aio_move $srcpath, $dstpath, $callback->($status)
459 Try to move the *file* (directories not supported as either source 673 Try to move the *file* (directories not supported as either source
460 or destination) from $srcpath to $dstpath and call the callback with 674 or destination) from $srcpath to $dstpath and call the callback with
461 the 0 (error) or -1 ok. 675 a status of 0 (ok) or -1 (error, see $!).
462 676
463 This is a composite request that tries to rename(2) the file first. 677 This is a composite request that tries to rename(2) the file first;
464 If rename files with "EXDEV", it copies the file with "aio_copy" 678 if rename fails with "EXDEV", it copies the file with "aio_copy"
465 and, if that is successful, unlinking the $srcpath. 679 and, if that is successful, unlinks the $srcpath.
466 680
467 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 681 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
468 Scans a directory (similar to "aio_readdir") but additionally tries 682 Scans a directory (similar to "aio_readdir") but additionally tries
469 to efficiently separate the entries of directory $path into two sets 683 to efficiently separate the entries of directory $path into two sets
470 of names, directories you can recurse into (directories), and ones 684 of names, directories you can recurse into (directories), and ones
… …
490 Implementation notes. 704 Implementation notes.
491 705
492 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry 706 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
493 can. 707 can.
494 708
709 If readdir returns file type information, then this is used directly
710 to find directories.
711
495 After reading the directory, the modification time, size etc. of the 712 Otherwise, after reading the directory, the modification time, size
496 directory before and after the readdir is checked, and if they match 713 etc. of the directory before and after the readdir is checked, and
497 (and isn't the current time), the link count will be used to decide 714 if they match (and isn't the current time), the link count will be
498 how many entries are directories (if >= 2). Otherwise, no knowledge 715 used to decide how many entries are directories (if >= 2).
499 of the number of subdirectories will be assumed. 716 Otherwise, no knowledge of the number of subdirectories will be
717 assumed.
500 718
501 Then entries will be sorted into likely directories (everything 719 Then entries will be sorted into likely directories a non-initial
502 without a non-initial dot currently) and likely non-directories 720 dot currently) and likely non-directories (see "aio_readdirx"). Then
503 (everything else). Then every entry plus an appended "/." will be 721 every entry plus an appended "/." will be "stat"'ed, likely
504 "stat"'ed, likely directories first. If that succeeds, it assumes 722 directories first, in order of their inode numbers. If that
505 that the entry is a directory or a symlink to directory (which will 723 succeeds, it assumes that the entry is a directory or a symlink to
506 be checked seperately). This is often faster than stat'ing the entry 724 directory (which will be checked seperately). This is often faster
507 itself because filesystems might detect the type of the entry 725 than stat'ing the entry itself because filesystems might detect the
508 without reading the inode data (e.g. ext2fs filetype feature). 726 type of the entry without reading the inode data (e.g. ext2fs
727 filetype feature), even on systems that cannot return the filetype
728 information on readdir.
509 729
510 If the known number of directories (link count - 2) has been 730 If the known number of directories (link count - 2) has been
511 reached, the rest of the entries is assumed to be non-directories. 731 reached, the rest of the entries is assumed to be non-directories.
512 732
513 This only works with certainty on POSIX (= UNIX) filesystems, which 733 This only works with certainty on POSIX (= UNIX) filesystems, which
… …
521 Delete a directory tree starting (and including) $path, return the 741 Delete a directory tree starting (and including) $path, return the
522 status of the final "rmdir" only. This is a composite request that 742 status of the final "rmdir" only. This is a composite request that
523 uses "aio_scandir" to recurse into and rmdir directories, and unlink 743 uses "aio_scandir" to recurse into and rmdir directories, and unlink
524 everything else. 744 everything else.
525 745
746 aio_sync $callback->($status)
747 Asynchronously call sync and call the callback when finished.
748
526 aio_fsync $fh, $callback->($status) 749 aio_fsync $fh, $callback->($status)
527 Asynchronously call fsync on the given filehandle and call the 750 Asynchronously call fsync on the given filehandle and call the
528 callback with the fsync result code. 751 callback with the fsync result code.
529 752
530 aio_fdatasync $fh, $callback->($status) 753 aio_fdatasync $fh, $callback->($status)
531 Asynchronously call fdatasync on the given filehandle and call the 754 Asynchronously call fdatasync on the given filehandle and call the
532 callback with the fdatasync result code. 755 callback with the fdatasync result code.
533 756
534 If this call isn't available because your OS lacks it or it couldn't 757 If this call isn't available because your OS lacks it or it couldn't
535 be detected, it will be emulated by calling "fsync" instead. 758 be detected, it will be emulated by calling "fsync" instead.
759
760 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
761 Sync the data portion of the file specified by $offset and $length
762 to disk (but NOT the metadata), by calling the Linux-specific
763 sync_file_range call. If sync_file_range is not available or it
764 returns ENOSYS, then fdatasync or fsync is being substituted.
765
766 $flags can be a combination of
767 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
768 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
769 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
770 manpage for details.
771
772 aio_pathsync $path, $callback->($status)
773 This request tries to open, fsync and close the given path. This is
774 a composite request intended to sync directories after directory
775 operations (E.g. rename). This might not work on all operating
776 systems or have any specific effect, but usually it makes sure that
777 directory changes get written to disc. It works for anything that
778 can be opened for read-only, not just directories.
779
780 Future versions of this function might fall back to other methods
781 when "fsync" on the directory fails (such as calling "sync").
782
783 Passes 0 when everything went ok, and -1 on error.
784
785 aio_msync $scalar, $offset = 0, $length = undef, flags = 0,
786 $callback->($status)
787 This is a rather advanced IO::AIO call, which only works on
788 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
789 also works on data scalars managed by the Sys::Mmap or Mmap modules,
790 note that the scalar must only be modified in-place while an aio
791 operation is pending on it).
792
793 It calls the "msync" function of your OS, if available, with the
794 memory area starting at $offset in the string and ending $length
795 bytes later. If $length is negative, counts from the end, and if
796 $length is "undef", then it goes till the end of the string. The
797 flags can be a combination of "IO::AIO::MS_ASYNC",
798 "IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC".
799
800 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
801 $callback->($status)
802 This is a rather advanced IO::AIO call, which works best on
803 mmap(2)ed scalars.
804
805 It touches (reads or writes) all memory pages in the specified range
806 inside the scalar. All caveats and parameters are the same as for
807 "aio_msync", above, except for flags, which must be either 0 (which
808 reads all pages and ensures they are instantiated) or
809 "IO::AIO::MT_MODIFY", which modifies the memory page s(by reading
810 and writing an octet from it, which dirties the page).
811
812 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
813 This is a rather advanced IO::AIO call, which works best on
814 mmap(2)ed scalars.
815
816 It reads in all the pages of the underlying storage into memory (if
817 any) and locks them, so they are not getting swapped/paged out or
818 removed.
819
820 If $length is undefined, then the scalar will be locked till the
821 end.
822
823 On systems that do not implement "mlock", this function returns -1
824 and sets errno to "ENOSYS".
825
826 Note that the corresponding "munlock" is synchronous and is
827 documented under "MISCELLANEOUS FUNCTIONS".
828
829 Example: open a file, mmap and mlock it - both will be undone when
830 $data gets destroyed.
831
832 open my $fh, "<", $path or die "$path: $!";
833 my $data;
834 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
835 aio_mlock $data; # mlock in background
836
837 aio_mlockall $flags, $callback->($status)
838 Calls the "mlockall" function with the given $flags (a combination
839 of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
840
841 On systems that do not implement "mlockall", this function returns
842 -1 and sets errno to "ENOSYS".
843
844 Note that the corresponding "munlockall" is synchronous and is
845 documented under "MISCELLANEOUS FUNCTIONS".
846
847 Example: asynchronously lock all current and future pages into
848 memory.
849
850 aio_mlockall IO::AIO::MCL_FUTURE;
536 851
537 aio_group $callback->(...) 852 aio_group $callback->(...)
538 This is a very special aio request: Instead of doing something, it 853 This is a very special aio request: Instead of doing something, it
539 is a container for other aio requests, which is useful if you want 854 is a container for other aio requests, which is useful if you want
540 to bundle many requests into a single, composite, request with a 855 to bundle many requests into a single, composite, request with a
… …
583 898
584 cancel $req 899 cancel $req
585 Cancels the request, if possible. Has the effect of skipping 900 Cancels the request, if possible. Has the effect of skipping
586 execution when entering the execute state and skipping calling the 901 execution when entering the execute state and skipping calling the
587 callback when entering the the result state, but will leave the 902 callback when entering the the result state, but will leave the
588 request otherwise untouched. That means that requests that currently 903 request otherwise untouched (with the exception of readdir). That
589 execute will not be stopped and resources held by the request will 904 means that requests that currently execute will not be stopped and
590 not be freed prematurely. 905 resources held by the request will not be freed prematurely.
591 906
592 cb $req $callback->(...) 907 cb $req $callback->(...)
593 Replace (or simply set) the callback registered to the request. 908 Replace (or simply set) the callback registered to the request.
594 909
595 IO::AIO::GRP CLASS 910 IO::AIO::GRP CLASS
… …
622 }; 937 };
623 938
624 This makes it very easy to create composite requests (see the source of 939 This makes it very easy to create composite requests (see the source of
625 "aio_move" for an application) that work and feel like simple requests. 940 "aio_move" for an application) that work and feel like simple requests.
626 941
627 * The IO::AIO::GRP objects will be cleaned up during calls to 942 * The IO::AIO::GRP objects will be cleaned up during calls to
628 "IO::AIO::poll_cb", just like any other request. 943 "IO::AIO::poll_cb", just like any other request.
944
629 * They can be canceled like any other request. Canceling will cancel not 945 * They can be canceled like any other request. Canceling will cancel
630 only the request itself, but also all requests it contains. 946 not only the request itself, but also all requests it contains.
947
631 * They can also can also be added to other IO::AIO::GRP objects. 948 * They can also can also be added to other IO::AIO::GRP objects.
949
632 * You must not add requests to a group from within the group callback 950 * You must not add requests to a group from within the group callback
633 (or any later time). 951 (or any later time).
634 952
635 Their lifetime, simplified, looks like this: when they are empty, they 953 Their lifetime, simplified, looks like this: when they are empty, they
636 will finish very quickly. If they contain only requests that are in the 954 will finish very quickly. If they contain only requests that are in the
637 "done" state, they will also finish. Otherwise they will continue to 955 "done" state, they will also finish. Otherwise they will continue to
638 exist. 956 exist.
639 957
640 That means after creating a group you have some time to add requests. 958 That means after creating a group you have some time to add requests
641 And in the callbacks of those requests, you can add further requests to 959 (precisely before the callback has been invoked, which is only done
642 the group. And only when all those requests have finished will the the 960 within the "poll_cb"). And in the callbacks of those requests, you can
643 group itself finish. 961 add further requests to the group. And only when all those requests have
962 finished will the the group itself finish.
644 963
645 add $grp ... 964 add $grp ...
646 $grp->add (...) 965 $grp->add (...)
647 Add one or more requests to the group. Any type of IO::AIO::REQ can 966 Add one or more requests to the group. Any type of IO::AIO::REQ can
648 be added, including other groups, as long as you do not create 967 be added, including other groups, as long as you do not create
… …
653 $grp->cancel_subs 972 $grp->cancel_subs
654 Cancel all subrequests and clears any feeder, but not the group 973 Cancel all subrequests and clears any feeder, but not the group
655 request itself. Useful when you queued a lot of events but got a 974 request itself. Useful when you queued a lot of events but got a
656 result early. 975 result early.
657 976
977 The group request will finish normally (you cannot add requests to
978 the group).
979
658 $grp->result (...) 980 $grp->result (...)
659 Set the result value(s) that will be passed to the group callback 981 Set the result value(s) that will be passed to the group callback
660 when all subrequests have finished and set thre groups errno to the 982 when all subrequests have finished and set the groups errno to the
661 current value of errno (just like calling "errno" without an error 983 current value of errno (just like calling "errno" without an error
662 number). By default, no argument will be passed and errno is zero. 984 number). By default, no argument will be passed and errno is zero.
663 985
664 $grp->errno ([$errno]) 986 $grp->errno ([$errno])
665 Sets the group errno value to $errno, or the current value of errno 987 Sets the group errno value to $errno, or the current value of errno
… …
691 does not impose any limits). 1013 does not impose any limits).
692 1014
693 If the feed does not queue more requests when called, it will be 1015 If the feed does not queue more requests when called, it will be
694 automatically removed from the group. 1016 automatically removed from the group.
695 1017
696 If the feed limit is 0, it will be set to 2 automatically. 1018 If the feed limit is 0 when this method is called, it will be set to
1019 2 automatically.
697 1020
698 Example: 1021 Example:
699 1022
700 # stat all files in @files, but only ever use four aio requests concurrently: 1023 # stat all files in @files, but only ever use four aio requests concurrently:
701 1024
… …
712 Sets the feeder limit for the group: The feeder will be called 1035 Sets the feeder limit for the group: The feeder will be called
713 whenever the group contains less than this many requests. 1036 whenever the group contains less than this many requests.
714 1037
715 Setting the limit to 0 will pause the feeding process. 1038 Setting the limit to 0 will pause the feeding process.
716 1039
1040 The default value for the limit is 0, but note that setting a feeder
1041 automatically bumps it up to 2.
1042
717 SUPPORT FUNCTIONS 1043 SUPPORT FUNCTIONS
718 EVENT PROCESSING AND EVENT LOOP INTEGRATION 1044 EVENT PROCESSING AND EVENT LOOP INTEGRATION
719 $fileno = IO::AIO::poll_fileno 1045 $fileno = IO::AIO::poll_fileno
720 Return the *request result pipe file descriptor*. This filehandle 1046 Return the *request result pipe file descriptor*. This filehandle
721 must be polled for reading by some mechanism outside this module 1047 must be polled for reading by some mechanism outside this module
722 (e.g. Event or select, see below or the SYNOPSIS). If the pipe 1048 (e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
723 becomes readable you have to call "poll_cb" to check the results. 1049 pipe becomes readable you have to call "poll_cb" to check the
1050 results.
724 1051
725 See "poll_cb" for an example. 1052 See "poll_cb" for an example.
726 1053
727 IO::AIO::poll_cb 1054 IO::AIO::poll_cb
728 Process some outstanding events on the result pipe. You have to call 1055 Process some outstanding events on the result pipe. You have to call
729 this regularly. Returns the number of events processed. Returns 1056 this regularly. Returns 0 if all events could be processed (or there
730 immediately when no events are outstanding. The amount of events 1057 were no events to process), or -1 if it returned earlier for
731 processed depends on the settings of "IO::AIO::max_poll_req" and 1058 whatever reason. Returns immediately when no events are outstanding.
732 "IO::AIO::max_poll_time". 1059 The amount of events processed depends on the settings of
1060 "IO::AIO::max_poll_req" and "IO::AIO::max_poll_time".
733 1061
734 If not all requests were processed for whatever reason, the 1062 If not all requests were processed for whatever reason, the
735 filehandle will still be ready when "poll_cb" returns. 1063 filehandle will still be ready when "poll_cb" returns, so normally
1064 you don't have to do anything special to have it called later.
1065
1066 Apart from calling "IO::AIO::poll_cb" when the event filehandle
1067 becomes ready, it can be beneficial to call this function from loops
1068 which submit a lot of requests, to make sure the results get
1069 processed when they become available and not just when the loop is
1070 finished and the event loop takes over again. This function returns
1071 very fast when there are no outstanding requests.
736 1072
737 Example: Install an Event watcher that automatically calls 1073 Example: Install an Event watcher that automatically calls
738 IO::AIO::poll_cb with high priority: 1074 IO::AIO::poll_cb with high priority (more examples can be found in
1075 the SYNOPSIS section, at the top of this document):
739 1076
740 Event->io (fd => IO::AIO::poll_fileno, 1077 Event->io (fd => IO::AIO::poll_fileno,
741 poll => 'r', async => 1, 1078 poll => 'r', async => 1,
742 cb => \&IO::AIO::poll_cb); 1079 cb => \&IO::AIO::poll_cb);
1080
1081 IO::AIO::poll_wait
1082 If there are any outstanding requests and none of them in the result
1083 phase, wait till the result filehandle becomes ready for reading
1084 (simply does a "select" on the filehandle. This is useful if you
1085 want to synchronously wait for some requests to finish).
1086
1087 See "nreqs" for an example.
1088
1089 IO::AIO::poll
1090 Waits until some requests have been handled.
1091
1092 Returns the number of requests processed, but is otherwise strictly
1093 equivalent to:
1094
1095 IO::AIO::poll_wait, IO::AIO::poll_cb
1096
1097 IO::AIO::flush
1098 Wait till all outstanding AIO requests have been handled.
1099
1100 Strictly equivalent to:
1101
1102 IO::AIO::poll_wait, IO::AIO::poll_cb
1103 while IO::AIO::nreqs;
743 1104
744 IO::AIO::max_poll_reqs $nreqs 1105 IO::AIO::max_poll_reqs $nreqs
745 IO::AIO::max_poll_time $seconds 1106 IO::AIO::max_poll_time $seconds
746 These set the maximum number of requests (default 0, meaning 1107 These set the maximum number of requests (default 0, meaning
747 infinity) that are being processed by "IO::AIO::poll_cb" in one 1108 infinity) that are being processed by "IO::AIO::poll_cb" in one
… …
771 # use a low priority so other tasks have priority 1132 # use a low priority so other tasks have priority
772 Event->io (fd => IO::AIO::poll_fileno, 1133 Event->io (fd => IO::AIO::poll_fileno,
773 poll => 'r', nice => 1, 1134 poll => 'r', nice => 1,
774 cb => &IO::AIO::poll_cb); 1135 cb => &IO::AIO::poll_cb);
775 1136
776 IO::AIO::poll_wait
777 If there are any outstanding requests and none of them in the result
778 phase, wait till the result filehandle becomes ready for reading
779 (simply does a "select" on the filehandle. This is useful if you
780 want to synchronously wait for some requests to finish).
781
782 See "nreqs" for an example.
783
784 IO::AIO::poll
785 Waits until some requests have been handled.
786
787 Returns the number of requests processed, but is otherwise strictly
788 equivalent to:
789
790 IO::AIO::poll_wait, IO::AIO::poll_cb
791
792 IO::AIO::flush
793 Wait till all outstanding AIO requests have been handled.
794
795 Strictly equivalent to:
796
797 IO::AIO::poll_wait, IO::AIO::poll_cb
798 while IO::AIO::nreqs;
799
800 CONTROLLING THE NUMBER OF THREADS 1137 CONTROLLING THE NUMBER OF THREADS
801 IO::AIO::min_parallel $nthreads 1138 IO::AIO::min_parallel $nthreads
802 Set the minimum number of AIO threads to $nthreads. The current 1139 Set the minimum number of AIO threads to $nthreads. The current
803 default is 8, which means eight asynchronous operations can execute 1140 default is 8, which means eight asynchronous operations can execute
804 concurrently at any one time (the number of outstanding requests, 1141 concurrently at any one time (the number of outstanding requests,
… …
833 1170
834 Under normal circumstances you don't need to call this function. 1171 Under normal circumstances you don't need to call this function.
835 1172
836 IO::AIO::max_idle $nthreads 1173 IO::AIO::max_idle $nthreads
837 Limit the number of threads (default: 4) that are allowed to idle 1174 Limit the number of threads (default: 4) that are allowed to idle
838 (i.e., threads that did not get a request to process within 10 1175 (i.e., threads that did not get a request to process within the idle
839 seconds). That means if a thread becomes idle while $nthreads other 1176 timeout (default: 10 seconds). That means if a thread becomes idle
840 threads are also idle, it will free its resources and exit. 1177 while $nthreads other threads are also idle, it will free its
1178 resources and exit.
841 1179
842 This is useful when you allow a large number of threads (e.g. 100 or 1180 This is useful when you allow a large number of threads (e.g. 100 or
843 1000) to allow for extremely high load situations, but want to free 1181 1000) to allow for extremely high load situations, but want to free
844 resources under normal circumstances (1000 threads can easily 1182 resources under normal circumstances (1000 threads can easily
845 consume 30MB of RAM). 1183 consume 30MB of RAM).
846 1184
847 The default is probably ok in most situations, especially if thread 1185 The default is probably ok in most situations, especially if thread
848 creation is fast. If thread creation is very slow on your system you 1186 creation is fast. If thread creation is very slow on your system you
849 might want to use larger values. 1187 might want to use larger values.
850 1188
1189 IO::AIO::idle_timeout $seconds
1190 Sets the minimum idle timeout (default 10) after which worker
1191 threads are allowed to exit. SEe "IO::AIO::max_idle".
1192
851 $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1193 IO::AIO::max_outstanding $maxreqs
1194 Sets the maximum number of outstanding requests to $nreqs. If you do
1195 queue up more than this number of requests, the next call to
1196 "IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
1197 "IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
1198 no longer exceeded.
1199
1200 In other words, this setting does not enforce a queue limit, but can
1201 be used to make poll functions block if the limit is exceeded.
1202
852 This is a very bad function to use in interactive programs because 1203 This is a very bad function to use in interactive programs because
853 it blocks, and a bad way to reduce concurrency because it is 1204 it blocks, and a bad way to reduce concurrency because it is
854 inexact: Better use an "aio_group" together with a feed callback. 1205 inexact: Better use an "aio_group" together with a feed callback.
855 1206
856 Sets the maximum number of outstanding requests to $nreqs. If you do 1207 It's main use is in scripts without an event loop - when you want to
857 queue up more than this number of requests, the next call to the 1208 stat a lot of files, you can write somehting like this:
858 "poll_cb" (and "poll_some" and other functions calling "poll_cb")
859 function will block until the limit is no longer exceeded.
860 1209
861 The default value is very large, so there is no practical limit on 1210 IO::AIO::max_outstanding 32;
1211
1212 for my $path (...) {
1213 aio_stat $path , ...;
1214 IO::AIO::poll_cb;
1215 }
1216
1217 IO::AIO::flush;
1218
1219 The call to "poll_cb" inside the loop will normally return
1220 instantly, but as soon as more thna 32 reqeusts are in-flight, it
1221 will block until some requests have been handled. This keeps the
1222 loop from pushing a large number of "aio_stat" requests onto the
1223 queue.
1224
1225 The default value for "max_outstanding" is very large, so there is
862 the number of outstanding requests. 1226 no practical limit on the number of outstanding requests.
863
864 You can still queue as many requests as you want. Therefore,
865 "max_oustsanding" is mainly useful in simple scripts (with low
866 values) or as a stop gap to shield against fatal memory overflow
867 (with large values).
868 1227
869 STATISTICAL INFORMATION 1228 STATISTICAL INFORMATION
870 IO::AIO::nreqs 1229 IO::AIO::nreqs
871 Returns the number of requests currently in the ready, execute or 1230 Returns the number of requests currently in the ready, execute or
872 pending states (i.e. for which their callback has not been invoked 1231 pending states (i.e. for which their callback has not been invoked
… …
883 1242
884 IO::AIO::npending 1243 IO::AIO::npending
885 Returns the number of requests currently in the pending state 1244 Returns the number of requests currently in the pending state
886 (executed, but not yet processed by poll_cb). 1245 (executed, but not yet processed by poll_cb).
887 1246
1247 MISCELLANEOUS FUNCTIONS
1248 IO::AIO implements some functions that might be useful, but are not
1249 asynchronous.
1250
1251 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1252 Calls the "eio_sendfile_sync" function, which is like
1253 "aio_sendfile", but is blocking (this makes most sense if you know
1254 the input data is likely cached already and the output filehandle is
1255 set to non-blocking operations).
1256
1257 Returns the number of bytes copied, or -1 on error.
1258
1259 IO::AIO::fadvise $fh, $offset, $len, $advice
1260 Simply calls the "posix_fadvise" function (see its manpage for
1261 details). The following advice constants are avaiable:
1262 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1263 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1264 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1265
1266 On systems that do not implement "posix_fadvise", this function
1267 returns ENOSYS, otherwise the return value of "posix_fadvise".
1268
1269 IO::AIO::madvise $scalar, $offset, $len, $advice
1270 Simply calls the "posix_madvise" function (see its manpage for
1271 details). The following advice constants are avaiable:
1272 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1273 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1274 "IO::AIO::MADV_DONTNEED".
1275
1276 On systems that do not implement "posix_madvise", this function
1277 returns ENOSYS, otherwise the return value of "posix_madvise".
1278
1279 IO::AIO::mprotect $scalar, $offset, $len, $protect
1280 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1281 $scalar (see its manpage for details). The following protect
1282 constants are avaiable: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1283 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1284
1285 On systems that do not implement "mprotect", this function returns
1286 ENOSYS, otherwise the return value of "mprotect".
1287
1288 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1289 Memory-maps a file (or anonymous memory range) and attaches it to
1290 the given $scalar, which will act like a string scalar.
1291
1292 The only operations allowed on the scalar are "substr"/"vec" that
1293 don't change the string length, and most read-only operations such
1294 as copying it or searching it with regexes and so on.
1295
1296 Anything else is unsafe and will, at best, result in memory leaks.
1297
1298 The memory map associated with the $scalar is automatically removed
1299 when the $scalar is destroyed, or when the "IO::AIO::mmap" or
1300 "IO::AIO::munmap" functions are called.
1301
1302 This calls the "mmap"(2) function internally. See your system's
1303 manual page for details on the $length, $prot and $flags parameters.
1304
1305 The $length must be larger than zero and smaller than the actual
1306 filesize.
1307
1308 $prot is a combination of "IO::AIO::PROT_NONE",
1309 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1310 "IO::AIO::PROT_WRITE",
1311
1312 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1313 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1314 not available, the are defined as 0): "IO::AIO::MAP_ANONYMOUS"
1315 (which is set to "MAP_ANON" if your system only provides this
1316 constant), "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED",
1317 "IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or
1318 "IO::AIO::MAP_NONBLOCK"
1319
1320 If $fh is "undef", then a file descriptor of -1 is passed.
1321
1322 $offset is the offset from the start of the file - it generally must
1323 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
1324
1325 Example:
1326
1327 use Digest::MD5;
1328 use IO::AIO;
1329
1330 open my $fh, "<verybigfile"
1331 or die "$!";
1332
1333 IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
1334 or die "verybigfile: $!";
1335
1336 my $fast_md5 = md5 $data;
1337
1338 IO::AIO::munmap $scalar
1339 Removes a previous mmap and undefines the $scalar.
1340
1341 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1342 Calls the "munlock" function, undoing the effects of a previous
1343 "aio_mlock" call (see its description for details).
1344
1345 IO::AIO::munlockall
1346 Calls the "munlockall" function.
1347
1348 On systems that do not implement "munlockall", this function returns
1349 ENOSYS, otherwise the return value of "munlockall".
1350
1351EVENT LOOP INTEGRATION
1352 It is recommended to use AnyEvent::AIO to integrate IO::AIO
1353 automatically into many event loops:
1354
1355 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
1356 use AnyEvent::AIO;
1357
1358 You can also integrate IO::AIO manually into many event loops, here are
1359 some examples of how to do this:
1360
1361 # EV integration
1362 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
1363
1364 # Event integration
1365 Event->io (fd => IO::AIO::poll_fileno,
1366 poll => 'r',
1367 cb => \&IO::AIO::poll_cb);
1368
1369 # Glib/Gtk2 integration
1370 add_watch Glib::IO IO::AIO::poll_fileno,
1371 in => sub { IO::AIO::poll_cb; 1 };
1372
1373 # Tk integration
1374 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
1375 readable => \&IO::AIO::poll_cb);
1376
1377 # Danga::Socket integration
1378 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1379 \&IO::AIO::poll_cb);
1380
888 FORK BEHAVIOUR 1381 FORK BEHAVIOUR
889 This module should do "the right thing" when the process using it forks: 1382 Usage of pthreads in a program changes the semantics of fork
1383 considerably. Specifically, only async-safe functions can be called
1384 after fork. Perl doesn't know about this, so in general, you cannot call
1385 fork with defined behaviour in perl if pthreads are involved. IO::AIO
1386 uses pthreads, so this applies, but many other extensions and (for
1387 inexplicable reasons) perl itself often is linked against pthreads, so
1388 this limitation applies to quite a lot of perls.
890 1389
891 Before the fork, IO::AIO enters a quiescent state where no requests can 1390 This module no longer tries to fight your OS, or POSIX. That means
892 be added in other threads and no results will be processed. After the 1391 IO::AIO only works in the process that loaded it. Forking is fully
893 fork the parent simply leaves the quiescent state and continues 1392 supported, but using IO::AIO in the child is not.
894 request/result processing, while the child frees the request/result
895 queue (so that the requests started before the fork will only be handled
896 in the parent). Threads will be started on demand until the limit set in
897 the parent process has been reached again.
898 1393
899 In short: the parent will, after a short pause, continue as if fork had 1394 You might get around by not *using* IO::AIO before (or after) forking.
900 not been called, while the child will act as if IO::AIO has not been 1395 You could also try to call the IO::AIO::reinit function in the child:
901 used yet. 1396
1397 IO::AIO::reinit
1398 Abondons all current requests and I/O threads and simply
1399 reinitialises all data structures. This is not an operation
1400 suppported by any standards, but happens to work on GNU/Linux and
1401 some newer BSD systems.
1402
1403 The only reasonable use for this function is to call it after
1404 forking, if "IO::AIO" was used in the parent. Calling it while
1405 IO::AIO is active in the process will result in undefined behaviour.
1406 Calling it at any time will also result in any undefined (by POSIX)
1407 behaviour.
902 1408
903 MEMORY USAGE 1409 MEMORY USAGE
904 Per-request usage: 1410 Per-request usage:
905 1411
906 Each aio request uses - depending on your architecture - around 100-200 1412 Each aio request uses - depending on your architecture - around 100-200
… …
920 1426
921KNOWN BUGS 1427KNOWN BUGS
922 Known bugs will be fixed in the next release. 1428 Known bugs will be fixed in the next release.
923 1429
924SEE ALSO 1430SEE ALSO
925 Coro::AIO. 1431 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
1432 more natural syntax.
926 1433
927AUTHOR 1434AUTHOR
928 Marc Lehmann <schmorp@schmorp.de> 1435 Marc Lehmann <schmorp@schmorp.de>
929 http://home.schmorp.de/ 1436 http://home.schmorp.de/
930 1437

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