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Revision 1.39 by root, Wed Aug 5 11:53:16 2009 UTC

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 (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
30 use AnyEvent::AIO;
31
29 # AnyEvent integration 32 # EV integration
30 open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!"; 33 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
31 my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
32 34
33 # Event integration 35 # Event integration
34 Event->io (fd => IO::AIO::poll_fileno, 36 Event->io (fd => IO::AIO::poll_fileno,
35 poll => 'r', 37 poll => 'r',
36 cb => \&IO::AIO::poll_cb); 38 cb => \&IO::AIO::poll_cb);
47 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno => 49 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
48 \&IO::AIO::poll_cb); 50 \&IO::AIO::poll_cb);
49 51
50DESCRIPTION 52DESCRIPTION
51 This module implements asynchronous I/O using whatever means your 53 This module implements asynchronous I/O using whatever means your
52 operating system supports. 54 operating system supports. It is implemented as an interface to "libeio"
55 (<http://software.schmorp.de/pkg/libeio.html>).
53 56
54 Asynchronous means that operations that can normally block your program 57 Asynchronous means that operations that can normally block your program
55 (e.g. reading from disk) will be done asynchronously: the operation will 58 (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 59 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 60 extremely useful for programs that need to stay interactive even when
61 faster on a RAID volume or over NFS when you do a number of stat 64 faster on a RAID volume or over NFS when you do a number of stat
62 operations concurrently. 65 operations concurrently.
63 66
64 While most of this works on all types of file descriptors (for example 67 While most of this works on all types of file descriptors (for example
65 sockets), using these functions on file descriptors that support 68 sockets), using these functions on file descriptors that support
66 nonblocking operation (again, sockets, pipes etc.) is very inefficient 69 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 70 Use an event loop for that (such as the EV module): IO::AIO will
69 into such an event loop itself. 71 naturally fit into such an event loop itself.
70 72
71 In this version, a number of threads are started that execute your 73 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 74 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 75 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 76 perl. In the future, this module might make use of the native aio
76 not well-supported or restricted (GNU/Linux doesn't allow them on normal 78 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 79 files currently, for example), and they would only support aio_read and
78 aio_write, so the remaining functionality would have to be implemented 80 aio_write, so the remaining functionality would have to be implemented
79 using threads anyway. 81 using threads anyway.
80 82
81 Although the module will work with in the presence of other (Perl-) 83 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 84 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 85 yourself, always call "poll_cb" from within the same thread, or never
84 never call "poll_cb" (or other "aio_" functions) recursively. 86 call "poll_cb" (or other "aio_" functions) recursively.
85 87
86 EXAMPLE 88 EXAMPLE
87 This is a simple example that uses the Event module and loads 89 This is a simple example that uses the EV module and loads /etc/passwd
88 /etc/passwd asynchronously: 90 asynchronously:
89 91
90 use Fcntl; 92 use Fcntl;
91 use Event; 93 use EV;
92 use IO::AIO; 94 use IO::AIO;
93 95
94 # register the IO::AIO callback with Event 96 # register the IO::AIO callback with EV
95 Event->io (fd => IO::AIO::poll_fileno, 97 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 98
99 # queue the request to open /etc/passwd 99 # queue the request to open /etc/passwd
100 aio_open "/etc/passwd", O_RDONLY, 0, sub { 100 aio_open "/etc/passwd", O_RDONLY, 0, sub {
101 my $fh = shift 101 my $fh = shift
102 or die "error while opening: $!"; 102 or die "error while opening: $!";
114 114
115 # file contents now in $contents 115 # file contents now in $contents
116 print $contents; 116 print $contents;
117 117
118 # exit event loop and program 118 # exit event loop and program
119 Event::unloop; 119 EV::unloop;
120 }; 120 };
121 }; 121 };
122 122
123 # possibly queue up other requests, or open GUI windows, 123 # possibly queue up other requests, or open GUI windows,
124 # check for sockets etc. etc. 124 # check for sockets etc. etc.
125 125
126 # process events as long as there are some: 126 # process events as long as there are some:
127 Event::loop; 127 EV::loop;
128 128
129REQUEST ANATOMY AND LIFETIME 129REQUEST ANATOMY AND LIFETIME
130 Every "aio_*" function creates a request. which is a C data structure 130 Every "aio_*" function creates a request. which is a C data structure
131 not directly visible to Perl. 131 not directly visible to Perl.
132 132
174 All the "aio_*" calls are more or less thin wrappers around the syscall 174 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 175 with the same name (sans "aio_"). The arguments are similar or
176 identical, and they all accept an additional (and optional) $callback 176 identical, and they all accept an additional (and optional) $callback
177 argument which must be a code reference. This code reference will get 177 argument which must be a code reference. This code reference will get
178 called with the syscall return code (e.g. most syscalls return -1 on 178 called with the syscall return code (e.g. most syscalls return -1 on
179 error, unlike perl, which usually delivers "false") as it's sole 179 error, unlike perl, which usually delivers "false") as its sole argument
180 argument when the given syscall has been executed asynchronously. 180 after the given syscall has been executed asynchronously.
181 181
182 All functions expecting a filehandle keep a copy of the filehandle 182 All functions expecting a filehandle keep a copy of the filehandle
183 internally until the request has finished. 183 internally until the request has finished.
184 184
185 All functions return request objects of type IO::AIO::REQ that allow 185 All functions return request objects of type IO::AIO::REQ that allow
198 the user environment, d) use Glib::filename_from_unicode on unicode 198 the user environment, d) use Glib::filename_from_unicode on unicode
199 filenames or e) use something else to ensure your scalar has the correct 199 filenames or e) use something else to ensure your scalar has the correct
200 contents. 200 contents.
201 201
202 This works, btw. independent of the internal UTF-8 bit, which IO::AIO 202 This works, btw. independent of the internal UTF-8 bit, which IO::AIO
203 handles correctly wether it is set or not. 203 handles correctly whether it is set or not.
204 204
205 $prev_pri = aioreq_pri [$pri] 205 $prev_pri = aioreq_pri [$pri]
206 Returns the priority value that would be used for the next request 206 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. 207 and, if $pri is given, sets the priority for the next aio request.
208 208
259 } 259 }
260 }; 260 };
261 261
262 aio_close $fh, $callback->($status) 262 aio_close $fh, $callback->($status)
263 Asynchronously close a file and call the callback with the result 263 Asynchronously close a file and call the callback with the result
264 code. *WARNING:* although accepted, you should not pass in a perl 264 code.
265 filehandle here, as perl will likely close the file descriptor
266 another time when the filehandle is destroyed. Normally, you can
267 safely call perls "close" or just let filehandles go out of scope.
268 265
269 This is supposed to be a bug in the API, so that might change. It's 266 Unfortunately, you can't do this to perl. Perl *insists* very
270 therefore best to avoid this function. 267 strongly on closing the file descriptor associated with the
268 filehandle itself.
269
270 Therefore, "aio_close" will not close the filehandle - instead it
271 will use dup2 to overwrite the file descriptor with the write-end of
272 a pipe (the pipe fd will be created on demand and will be cached).
273
274 Or in other words: the file descriptor will be closed, but it will
275 not be free for reuse until the perl filehandle is closed.
271 276
272 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 277 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
273 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 278 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
274 Reads or writes "length" bytes from the specified "fh" and "offset" 279 Reads or writes $length bytes from or to the specified $fh and
275 into the scalar given by "data" and offset "dataoffset" and calls 280 $offset into the scalar given by $data and offset $dataoffset and
276 the callback without the actual number of bytes read (or -1 on 281 calls the callback without the actual number of bytes read (or -1 on
277 error, just like the syscall). 282 error, just like the syscall).
278 283
284 "aio_read" will, like "sysread", shrink or grow the $data scalar to
285 offset plus the actual number of bytes read.
286
287 If $offset is undefined, then the current file descriptor offset
288 will be used (and updated), otherwise the file descriptor offset
289 will not be changed by these calls.
290
291 If $length is undefined in "aio_write", use the remaining length of
292 $data.
293
294 If $dataoffset is less than zero, it will be counted from the end of
295 $data.
296
279 The $data scalar *MUST NOT* be modified in any way while the request 297 The $data scalar *MUST NOT* be modified in any way while the request
280 is outstanding. Modifying it can result in segfaults or WW3 (if the 298 is outstanding. Modifying it can result in segfaults or World War
281 necessary/optional hardware is installed). 299 III (if the necessary/optional hardware is installed).
282 300
283 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at 301 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
284 offset 0 within the scalar: 302 offset 0 within the scalar:
285 303
286 aio_read $fh, 7, 15, $buffer, 0, sub { 304 aio_read $fh, 7, 15, $buffer, 0, sub {
344 aio_stat "/etc/passwd", sub { 362 aio_stat "/etc/passwd", sub {
345 $_[0] and die "stat failed: $!"; 363 $_[0] and die "stat failed: $!";
346 print "size is ", -s _, "\n"; 364 print "size is ", -s _, "\n";
347 }; 365 };
348 366
367 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
368 Works like perl's "utime" function (including the special case of
369 $atime and $mtime being undef). Fractional times are supported if
370 the underlying syscalls support them.
371
372 When called with a pathname, uses utimes(2) if available, otherwise
373 utime(2). If called on a file descriptor, uses futimes(2) if
374 available, otherwise returns ENOSYS, so this is not portable.
375
376 Examples:
377
378 # set atime and mtime to current time (basically touch(1)):
379 aio_utime "path", undef, undef;
380 # set atime to current time and mtime to beginning of the epoch:
381 aio_utime "path", time, undef; # undef==0
382
383 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
384 Works like perl's "chown" function, except that "undef" for either
385 $uid or $gid is being interpreted as "do not change" (but -1 can
386 also be used).
387
388 Examples:
389
390 # same as "chown root path" in the shell:
391 aio_chown "path", 0, -1;
392 # same as above:
393 aio_chown "path", 0, undef;
394
395 aio_truncate $fh_or_path, $offset, $callback->($status)
396 Works like truncate(2) or ftruncate(2).
397
398 aio_chmod $fh_or_path, $mode, $callback->($status)
399 Works like perl's "chmod" function.
400
349 aio_unlink $pathname, $callback->($status) 401 aio_unlink $pathname, $callback->($status)
350 Asynchronously unlink (delete) a file and call the callback with the 402 Asynchronously unlink (delete) a file and call the callback with the
351 result code. 403 result code.
352 404
353 aio_mknod $path, $mode, $dev, $callback->($status) 405 aio_mknod $path, $mode, $dev, $callback->($status)
389 aio_readdir $pathname, $callback->($entries) 441 aio_readdir $pathname, $callback->($entries)
390 Unlike the POSIX call of the same name, "aio_readdir" reads an 442 Unlike the POSIX call of the same name, "aio_readdir" reads an
391 entire directory (i.e. opendir + readdir + closedir). The entries 443 entire directory (i.e. opendir + readdir + closedir). The entries
392 will not be sorted, and will NOT include the "." and ".." entries. 444 will not be sorted, and will NOT include the "." and ".." entries.
393 445
394 The callback a single argument which is either "undef" or an 446 The callback is passed a single argument which is either "undef" or
395 array-ref with the filenames. 447 an array-ref with the filenames.
448
449 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
450 Quite similar to "aio_readdir", but the $flags argument allows to
451 tune behaviour and output format. In case of an error, $entries will
452 be "undef".
453
454 The flags are a combination of the following constants, ORed
455 together (the flags will also be passed to the callback, possibly
456 modified):
457
458 IO::AIO::READDIR_DENTS
459 When this flag is off, then the callback gets an arrayref with
460 of names only (as with "aio_readdir"), otherwise it gets an
461 arrayref with "[$name, $type, $inode]" arrayrefs, each
462 describing a single directory entry in more detail.
463
464 $name is the name of the entry.
465
466 $type is one of the "IO::AIO::DT_xxx" constants:
467
468 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
469 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
470 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
471
472 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
473 you need to know, you have to run stat yourself. Also, for speed
474 reasons, the $type scalars are read-only: you can not modify
475 them.
476
477 $inode is the inode number (which might not be exact on systems
478 with 64 bit inode numbers and 32 bit perls). This field has
479 unspecified content on systems that do not deliver the inode
480 information.
481
482 IO::AIO::READDIR_DIRS_FIRST
483 When this flag is set, then the names will be returned in an
484 order where likely directories come first. This is useful when
485 you need to quickly find directories, or you want to find all
486 directories while avoiding to stat() each entry.
487
488 If the system returns type information in readdir, then this is
489 used to find directories directly. Otherwise, likely directories
490 are files beginning with ".", or otherwise files with no dots,
491 of which files with short names are tried first.
492
493 IO::AIO::READDIR_STAT_ORDER
494 When this flag is set, then the names will be returned in an
495 order suitable for stat()'ing each one. That is, when you plan
496 to stat() all files in the given directory, then the returned
497 order will likely be fastest.
498
499 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
500 specified, then the likely dirs come first, resulting in a less
501 optimal stat order.
502
503 IO::AIO::READDIR_FOUND_UNKNOWN
504 This flag should not be set when calling "aio_readdirx".
505 Instead, it is being set by "aio_readdirx", when any of the
506 $type's found were "IO::AIO::DT_UNKNOWN". The absense of this
507 flag therefore indicates that all $type's are known, which can
508 be used to speed up some algorithms.
396 509
397 aio_load $path, $data, $callback->($status) 510 aio_load $path, $data, $callback->($status)
398 This is a composite request that tries to fully load the given file 511 This is a composite request that tries to fully load the given file
399 into memory. Status is the same as with aio_read. 512 into memory. Status is the same as with aio_read.
400 513
401 aio_copy $srcpath, $dstpath, $callback->($status) 514 aio_copy $srcpath, $dstpath, $callback->($status)
402 Try to copy the *file* (directories not supported as either source 515 Try to copy the *file* (directories not supported as either source
403 or destination) from $srcpath to $dstpath and call the callback with 516 or destination) from $srcpath to $dstpath and call the callback with
404 the 0 (error) or -1 ok. 517 the 0 (error) or -1 ok.
405 518
406 This is a composite request that it creates the destination file 519 This is a composite request that creates the destination file with
407 with mode 0200 and copies the contents of the source file into it 520 mode 0200 and copies the contents of the source file into it using
408 using "aio_sendfile", followed by restoring atime, mtime, access 521 "aio_sendfile", followed by restoring atime, mtime, access mode and
409 mode and uid/gid, in that order. 522 uid/gid, in that order.
410 523
411 If an error occurs, the partial destination file will be unlinked, 524 If an error occurs, the partial destination file will be unlinked,
412 if possible, except when setting atime, mtime, access mode and 525 if possible, except when setting atime, mtime, access mode and
413 uid/gid, where errors are being ignored. 526 uid/gid, where errors are being ignored.
414 527
415 aio_move $srcpath, $dstpath, $callback->($status) 528 aio_move $srcpath, $dstpath, $callback->($status)
416 Try to move the *file* (directories not supported as either source 529 Try to move the *file* (directories not supported as either source
417 or destination) from $srcpath to $dstpath and call the callback with 530 or destination) from $srcpath to $dstpath and call the callback with
418 the 0 (error) or -1 ok. 531 the 0 (error) or -1 ok.
419 532
420 This is a composite request that tries to rename(2) the file first. 533 This is a composite request that tries to rename(2) the file first;
421 If rename files with "EXDEV", it copies the file with "aio_copy" 534 if rename fails with "EXDEV", it copies the file with "aio_copy"
422 and, if that is successful, unlinking the $srcpath. 535 and, if that is successful, unlinks the $srcpath.
423 536
424 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 537 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
425 Scans a directory (similar to "aio_readdir") but additionally tries 538 Scans a directory (similar to "aio_readdir") but additionally tries
426 to efficiently separate the entries of directory $path into two sets 539 to efficiently separate the entries of directory $path into two sets
427 of names, directories you can recurse into (directories), and ones 540 of names, directories you can recurse into (directories), and ones
447 Implementation notes. 560 Implementation notes.
448 561
449 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry 562 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
450 can. 563 can.
451 564
565 If readdir returns file type information, then this is used directly
566 to find directories.
567
452 After reading the directory, the modification time, size etc. of the 568 Otherwise, after reading the directory, the modification time, size
453 directory before and after the readdir is checked, and if they match 569 etc. of the directory before and after the readdir is checked, and
454 (and isn't the current time), the link count will be used to decide 570 if they match (and isn't the current time), the link count will be
455 how many entries are directories (if >= 2). Otherwise, no knowledge 571 used to decide how many entries are directories (if >= 2).
456 of the number of subdirectories will be assumed. 572 Otherwise, no knowledge of the number of subdirectories will be
573 assumed.
457 574
458 Then entries will be sorted into likely directories (everything 575 Then entries will be sorted into likely directories a non-initial
459 without a non-initial dot currently) and likely non-directories 576 dot currently) and likely non-directories (see "aio_readdirx"). Then
460 (everything else). Then every entry plus an appended "/." will be 577 every entry plus an appended "/." will be "stat"'ed, likely
461 "stat"'ed, likely directories first. If that succeeds, it assumes 578 directories first, in order of their inode numbers. If that
462 that the entry is a directory or a symlink to directory (which will 579 succeeds, it assumes that the entry is a directory or a symlink to
463 be checked seperately). This is often faster than stat'ing the entry 580 directory (which will be checked seperately). This is often faster
464 itself because filesystems might detect the type of the entry 581 than stat'ing the entry itself because filesystems might detect the
465 without reading the inode data (e.g. ext2fs filetype feature). 582 type of the entry without reading the inode data (e.g. ext2fs
583 filetype feature), even on systems that cannot return the filetype
584 information on readdir.
466 585
467 If the known number of directories (link count - 2) has been 586 If the known number of directories (link count - 2) has been
468 reached, the rest of the entries is assumed to be non-directories. 587 reached, the rest of the entries is assumed to be non-directories.
469 588
470 This only works with certainty on POSIX (= UNIX) filesystems, which 589 This only works with certainty on POSIX (= UNIX) filesystems, which
478 Delete a directory tree starting (and including) $path, return the 597 Delete a directory tree starting (and including) $path, return the
479 status of the final "rmdir" only. This is a composite request that 598 status of the final "rmdir" only. This is a composite request that
480 uses "aio_scandir" to recurse into and rmdir directories, and unlink 599 uses "aio_scandir" to recurse into and rmdir directories, and unlink
481 everything else. 600 everything else.
482 601
602 aio_sync $callback->($status)
603 Asynchronously call sync and call the callback when finished.
604
483 aio_fsync $fh, $callback->($status) 605 aio_fsync $fh, $callback->($status)
484 Asynchronously call fsync on the given filehandle and call the 606 Asynchronously call fsync on the given filehandle and call the
485 callback with the fsync result code. 607 callback with the fsync result code.
486 608
487 aio_fdatasync $fh, $callback->($status) 609 aio_fdatasync $fh, $callback->($status)
488 Asynchronously call fdatasync on the given filehandle and call the 610 Asynchronously call fdatasync on the given filehandle and call the
489 callback with the fdatasync result code. 611 callback with the fdatasync result code.
490 612
491 If this call isn't available because your OS lacks it or it couldn't 613 If this call isn't available because your OS lacks it or it couldn't
492 be detected, it will be emulated by calling "fsync" instead. 614 be detected, it will be emulated by calling "fsync" instead.
615
616 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
617 Sync the data portion of the file specified by $offset and $length
618 to disk (but NOT the metadata), by calling the Linux-specific
619 sync_file_range call. If sync_file_range is not available or it
620 returns ENOSYS, then fdatasync or fsync is being substituted.
621
622 $flags can be a combination of
623 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
624 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
625 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
626 manpage for details.
627
628 aio_pathsync $path, $callback->($status)
629 This request tries to open, fsync and close the given path. This is
630 a composite request intended to sync directories after directory
631 operations (E.g. rename). This might not work on all operating
632 systems or have any specific effect, but usually it makes sure that
633 directory changes get written to disc. It works for anything that
634 can be opened for read-only, not just directories.
635
636 Future versions of this function might fall back to other methods
637 when "fsync" on the directory fails (such as calling "sync").
638
639 Passes 0 when everything went ok, and -1 on error.
493 640
494 aio_group $callback->(...) 641 aio_group $callback->(...)
495 This is a very special aio request: Instead of doing something, it 642 This is a very special aio request: Instead of doing something, it
496 is a container for other aio requests, which is useful if you want 643 is a container for other aio requests, which is useful if you want
497 to bundle many requests into a single, composite, request with a 644 to bundle many requests into a single, composite, request with a
540 687
541 cancel $req 688 cancel $req
542 Cancels the request, if possible. Has the effect of skipping 689 Cancels the request, if possible. Has the effect of skipping
543 execution when entering the execute state and skipping calling the 690 execution when entering the execute state and skipping calling the
544 callback when entering the the result state, but will leave the 691 callback when entering the the result state, but will leave the
545 request otherwise untouched. That means that requests that currently 692 request otherwise untouched (with the exception of readdir). That
546 execute will not be stopped and resources held by the request will 693 means that requests that currently execute will not be stopped and
547 not be freed prematurely. 694 resources held by the request will not be freed prematurely.
548 695
549 cb $req $callback->(...) 696 cb $req $callback->(...)
550 Replace (or simply set) the callback registered to the request. 697 Replace (or simply set) the callback registered to the request.
551 698
552 IO::AIO::GRP CLASS 699 IO::AIO::GRP CLASS
579 }; 726 };
580 727
581 This makes it very easy to create composite requests (see the source of 728 This makes it very easy to create composite requests (see the source of
582 "aio_move" for an application) that work and feel like simple requests. 729 "aio_move" for an application) that work and feel like simple requests.
583 730
584 * The IO::AIO::GRP objects will be cleaned up during calls to 731 * The IO::AIO::GRP objects will be cleaned up during calls to
585 "IO::AIO::poll_cb", just like any other request. 732 "IO::AIO::poll_cb", just like any other request.
733
586 * They can be canceled like any other request. Canceling will cancel not 734 * They can be canceled like any other request. Canceling will cancel
587 only the request itself, but also all requests it contains. 735 not only the request itself, but also all requests it contains.
736
588 * They can also can also be added to other IO::AIO::GRP objects. 737 * They can also can also be added to other IO::AIO::GRP objects.
738
589 * You must not add requests to a group from within the group callback 739 * You must not add requests to a group from within the group callback
590 (or any later time). 740 (or any later time).
591 741
592 Their lifetime, simplified, looks like this: when they are empty, they 742 Their lifetime, simplified, looks like this: when they are empty, they
593 will finish very quickly. If they contain only requests that are in the 743 will finish very quickly. If they contain only requests that are in the
594 "done" state, they will also finish. Otherwise they will continue to 744 "done" state, they will also finish. Otherwise they will continue to
595 exist. 745 exist.
596 746
597 That means after creating a group you have some time to add requests. 747 That means after creating a group you have some time to add requests
598 And in the callbacks of those requests, you can add further requests to 748 (precisely before the callback has been invoked, which is only done
599 the group. And only when all those requests have finished will the the 749 within the "poll_cb"). And in the callbacks of those requests, you can
600 group itself finish. 750 add further requests to the group. And only when all those requests have
751 finished will the the group itself finish.
601 752
602 add $grp ... 753 add $grp ...
603 $grp->add (...) 754 $grp->add (...)
604 Add one or more requests to the group. Any type of IO::AIO::REQ can 755 Add one or more requests to the group. Any type of IO::AIO::REQ can
605 be added, including other groups, as long as you do not create 756 be added, including other groups, as long as you do not create
612 request itself. Useful when you queued a lot of events but got a 763 request itself. Useful when you queued a lot of events but got a
613 result early. 764 result early.
614 765
615 $grp->result (...) 766 $grp->result (...)
616 Set the result value(s) that will be passed to the group callback 767 Set the result value(s) that will be passed to the group callback
617 when all subrequests have finished and set thre groups errno to the 768 when all subrequests have finished and set the groups errno to the
618 current value of errno (just like calling "errno" without an error 769 current value of errno (just like calling "errno" without an error
619 number). By default, no argument will be passed and errno is zero. 770 number). By default, no argument will be passed and errno is zero.
620 771
621 $grp->errno ([$errno]) 772 $grp->errno ([$errno])
622 Sets the group errno value to $errno, or the current value of errno 773 Sets the group errno value to $errno, or the current value of errno
648 does not impose any limits). 799 does not impose any limits).
649 800
650 If the feed does not queue more requests when called, it will be 801 If the feed does not queue more requests when called, it will be
651 automatically removed from the group. 802 automatically removed from the group.
652 803
653 If the feed limit is 0, it will be set to 2 automatically. 804 If the feed limit is 0 when this method is called, it will be set to
805 2 automatically.
654 806
655 Example: 807 Example:
656 808
657 # stat all files in @files, but only ever use four aio requests concurrently: 809 # stat all files in @files, but only ever use four aio requests concurrently:
658 810
669 Sets the feeder limit for the group: The feeder will be called 821 Sets the feeder limit for the group: The feeder will be called
670 whenever the group contains less than this many requests. 822 whenever the group contains less than this many requests.
671 823
672 Setting the limit to 0 will pause the feeding process. 824 Setting the limit to 0 will pause the feeding process.
673 825
826 The default value for the limit is 0, but note that setting a feeder
827 automatically bumps it up to 2.
828
674 SUPPORT FUNCTIONS 829 SUPPORT FUNCTIONS
675 EVENT PROCESSING AND EVENT LOOP INTEGRATION 830 EVENT PROCESSING AND EVENT LOOP INTEGRATION
676 $fileno = IO::AIO::poll_fileno 831 $fileno = IO::AIO::poll_fileno
677 Return the *request result pipe file descriptor*. This filehandle 832 Return the *request result pipe file descriptor*. This filehandle
678 must be polled for reading by some mechanism outside this module 833 must be polled for reading by some mechanism outside this module
679 (e.g. Event or select, see below or the SYNOPSIS). If the pipe 834 (e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
680 becomes readable you have to call "poll_cb" to check the results. 835 pipe becomes readable you have to call "poll_cb" to check the
836 results.
681 837
682 See "poll_cb" for an example. 838 See "poll_cb" for an example.
683 839
684 IO::AIO::poll_cb 840 IO::AIO::poll_cb
685 Process some outstanding events on the result pipe. You have to call 841 Process some outstanding events on the result pipe. You have to call
686 this regularly. Returns the number of events processed. Returns 842 this regularly. Returns 0 if all events could be processed, or -1 if
687 immediately when no events are outstanding. The amount of events 843 it returned earlier for whatever reason. Returns immediately when no
844 events are outstanding. The amount of events processed depends on
688 processed depends on the settings of "IO::AIO::max_poll_req" and 845 the settings of "IO::AIO::max_poll_req" and
689 "IO::AIO::max_poll_time". 846 "IO::AIO::max_poll_time".
690 847
691 If not all requests were processed for whatever reason, the 848 If not all requests were processed for whatever reason, the
692 filehandle will still be ready when "poll_cb" returns. 849 filehandle will still be ready when "poll_cb" returns, so normally
850 you don't have to do anything special to have it called later.
693 851
694 Example: Install an Event watcher that automatically calls 852 Example: Install an Event watcher that automatically calls
695 IO::AIO::poll_cb with high priority: 853 IO::AIO::poll_cb with high priority (more examples can be found in
854 the SYNOPSIS section, at the top of this document):
696 855
697 Event->io (fd => IO::AIO::poll_fileno, 856 Event->io (fd => IO::AIO::poll_fileno,
698 poll => 'r', async => 1, 857 poll => 'r', async => 1,
699 cb => \&IO::AIO::poll_cb); 858 cb => \&IO::AIO::poll_cb);
700 859
803 962
804 The default is probably ok in most situations, especially if thread 963 The default is probably ok in most situations, especially if thread
805 creation is fast. If thread creation is very slow on your system you 964 creation is fast. If thread creation is very slow on your system you
806 might want to use larger values. 965 might want to use larger values.
807 966
808 $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 967 IO::AIO::max_outstanding $maxreqs
809 This is a very bad function to use in interactive programs because 968 This is a very bad function to use in interactive programs because
810 it blocks, and a bad way to reduce concurrency because it is 969 it blocks, and a bad way to reduce concurrency because it is
811 inexact: Better use an "aio_group" together with a feed callback. 970 inexact: Better use an "aio_group" together with a feed callback.
812 971
813 Sets the maximum number of outstanding requests to $nreqs. If you to 972 Sets the maximum number of outstanding requests to $nreqs. If you do
814 queue up more than this number of requests, the next call to the 973 queue up more than this number of requests, the next call to the
815 "poll_cb" (and "poll_some" and other functions calling "poll_cb") 974 "poll_cb" (and "poll_some" and other functions calling "poll_cb")
816 function will block until the limit is no longer exceeded. 975 function will block until the limit is no longer exceeded.
817 976
818 The default value is very large, so there is no practical limit on 977 The default value is very large, so there is no practical limit on
819 the number of outstanding requests. 978 the number of outstanding requests.
820 979
821 You can still queue as many requests as you want. Therefore, 980 You can still queue as many requests as you want. Therefore,
822 "max_oustsanding" is mainly useful in simple scripts (with low 981 "max_outstanding" is mainly useful in simple scripts (with low
823 values) or as a stop gap to shield against fatal memory overflow 982 values) or as a stop gap to shield against fatal memory overflow
824 (with large values). 983 (with large values).
825 984
826 STATISTICAL INFORMATION 985 STATISTICAL INFORMATION
827 IO::AIO::nreqs 986 IO::AIO::nreqs
839 executed). 998 executed).
840 999
841 IO::AIO::npending 1000 IO::AIO::npending
842 Returns the number of requests currently in the pending state 1001 Returns the number of requests currently in the pending state
843 (executed, but not yet processed by poll_cb). 1002 (executed, but not yet processed by poll_cb).
1003
1004 MISCELLANEOUS FUNCTIONS
1005 IO::AIO implements some functions that might be useful, but are not
1006 asynchronous.
1007
1008 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1009 Calls the "eio_sendfile_sync" function, which is like
1010 "aio_sendfile", but is blocking (this makes most sense if you know
1011 the input data is likely cached already and the output filehandle is
1012 set to non-blocking operations).
1013
1014 Returns the number of bytes copied, or -1 on error.
1015
1016 IO::AIO::fadvise $fh, $offset, $len, $advice
1017 Simply calls the "posix_fadvise" function (see it's manpage for
1018 details). The following advice constants are avaiable:
1019 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1020 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1021 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1022
1023 On systems that do not implement "posix_fadvise", this function
1024 returns ENOSYS, otherwise the return value of "posix_fadvise".
844 1025
845 FORK BEHAVIOUR 1026 FORK BEHAVIOUR
846 This module should do "the right thing" when the process using it forks: 1027 This module should do "the right thing" when the process using it forks:
847 1028
848 Before the fork, IO::AIO enters a quiescent state where no requests can 1029 Before the fork, IO::AIO enters a quiescent state where no requests can
864 bytes of memory. In addition, stat requests need a stat buffer (possibly 1045 bytes of memory. In addition, stat requests need a stat buffer (possibly
865 a few hundred bytes), readdir requires a result buffer and so on. Perl 1046 a few hundred bytes), readdir requires a result buffer and so on. Perl
866 scalars and other data passed into aio requests will also be locked and 1047 scalars and other data passed into aio requests will also be locked and
867 will consume memory till the request has entered the done state. 1048 will consume memory till the request has entered the done state.
868 1049
869 This is now awfully much, so queuing lots of requests is not usually a 1050 This is not awfully much, so queuing lots of requests is not usually a
870 problem. 1051 problem.
871 1052
872 Per-thread usage: 1053 Per-thread usage:
873 1054
874 In the execution phase, some aio requests require more memory for 1055 In the execution phase, some aio requests require more memory for
877 1058
878KNOWN BUGS 1059KNOWN BUGS
879 Known bugs will be fixed in the next release. 1060 Known bugs will be fixed in the next release.
880 1061
881SEE ALSO 1062SEE ALSO
882 Coro::AIO. 1063 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
1064 more natural syntax.
883 1065
884AUTHOR 1066AUTHOR
885 Marc Lehmann <schmorp@schmorp.de> 1067 Marc Lehmann <schmorp@schmorp.de>
886 http://home.schmorp.de/ 1068 http://home.schmorp.de/
887 1069

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