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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.9 by root, Sun Jul 10 22:20:55 2005 UTC vs.
Revision 1.86 by root, Sat Oct 28 23:32:29 2006 UTC

15 15
16 aio_read $fh, 30000, 1024, $buffer, 0, sub { 16 aio_read $fh, 30000, 1024, $buffer, 0, sub {
17 $_[0] > 0 or die "read error: $!"; 17 $_[0] > 0 or die "read error: $!";
18 }; 18 };
19 19
20 # Event 20 # version 2+ has request and group objects
21 use IO::AIO 2;
22
23 aioreq_pri 4; # give next request a very high priority
24 my $req = aio_unlink "/tmp/file", sub { };
25 $req->cancel; # cancel request if still in queue
26
27 my $grp = aio_group sub { print "all stats done\n" };
28 add $grp aio_stat "..." for ...;
29
30 # AnyEvent integration
31 open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
32 my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
33
34 # Event integration
21 Event->io (fd => IO::AIO::poll_fileno, 35 Event->io (fd => IO::AIO::poll_fileno,
22 poll => 'r', 36 poll => 'r',
23 cb => \&IO::AIO::poll_cb); 37 cb => \&IO::AIO::poll_cb);
24 38
25 # Glib/Gtk2 39 # Glib/Gtk2 integration
26 add_watch Glib::IO IO::AIO::poll_fileno, 40 add_watch Glib::IO IO::AIO::poll_fileno,
27 \&IO::AIO::poll_cb; 41 in => sub { IO::AIO::poll_cb; 1 };
28 42
29 # Tk 43 # Tk integration
30 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "", 44 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
31 readable => \&IO::AIO::poll_cb); 45 readable => \&IO::AIO::poll_cb);
32 46
47 # Danga::Socket integration
48 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
49 \&IO::AIO::poll_cb);
50
33=head1 DESCRIPTION 51=head1 DESCRIPTION
34 52
35This module implements asynchronous I/O using whatever means your 53This module implements asynchronous I/O using whatever means your
36operating system supports. 54operating system supports.
37 55
56Asynchronous means that operations that can normally block your program
57(e.g. reading from disk) will be done asynchronously: the operation
58will still block, but you can do something else in the meantime. This
59is extremely useful for programs that need to stay interactive even
60when doing heavy I/O (GUI programs, high performance network servers
61etc.), but can also be used to easily do operations in parallel that are
62normally done sequentially, e.g. stat'ing many files, which is much faster
63on a RAID volume or over NFS when you do a number of stat operations
64concurrently.
65
66While this works on all types of file descriptors (for example sockets),
67using these functions on file descriptors that support nonblocking
68operation (again, sockets, pipes etc.) is very inefficient. Use an event
69loop for that (such as the L<Event|Event> module): IO::AIO will naturally
70fit into such an event loop itself.
71
38Currently, a number of threads are started that execute your read/writes 72In this version, a number of threads are started that execute your
39and signal their completion. You don't need thread support in your libc or 73requests and signal their completion. You don't need thread support
40perl, and the threads created by this module will not be visible to the 74in perl, and the threads created by this module will not be visible
41pthreads library. In the future, this module might make use of the native 75to perl. In the future, this module might make use of the native aio
42aio functions available on many operating systems. However, they are often 76functions available on many operating systems. However, they are often
43not well-supported (Linux doesn't allow them on normal files currently, 77not well-supported or restricted (GNU/Linux doesn't allow them on normal
44for example), and they would only support aio_read and aio_write, so the 78files currently, for example), and they would only support aio_read and
45remaining functionality would have to be implemented using threads anyway. 79aio_write, so the remaining functionality would have to be implemented
80using threads anyway.
46 81
47Although the module will work with in the presence of other threads, it is 82Although the module will work with in the presence of other (Perl-)
48currently not reentrant, so use appropriate locking yourself. 83threads, it is currently not reentrant in any way, so use appropriate
84locking yourself, always call C<poll_cb> from within the same thread, or
85never call C<poll_cb> (or other C<aio_> functions) recursively.
86
87=head2 EXAMPLE
88
89This is a simple example that uses the Event module and loads
90F</etc/passwd> asynchronously:
91
92 use Fcntl;
93 use Event;
94 use IO::AIO;
95
96 # register the IO::AIO callback with Event
97 Event->io (fd => IO::AIO::poll_fileno,
98 poll => 'r',
99 cb => \&IO::AIO::poll_cb);
100
101 # queue the request to open /etc/passwd
102 aio_open "/etc/passwd", O_RDONLY, 0, sub {
103 my $fh = $_[0]
104 or die "error while opening: $!";
105
106 # stat'ing filehandles is generally non-blocking
107 my $size = -s $fh;
108
109 # queue a request to read the file
110 my $contents;
111 aio_read $fh, 0, $size, $contents, 0, sub {
112 $_[0] == $size
113 or die "short read: $!";
114
115 close $fh;
116
117 # file contents now in $contents
118 print $contents;
119
120 # exit event loop and program
121 Event::unloop;
122 };
123 };
124
125 # possibly queue up other requests, or open GUI windows,
126 # check for sockets etc. etc.
127
128 # process events as long as there are some:
129 Event::loop;
130
131=head1 REQUEST ANATOMY AND LIFETIME
132
133Every C<aio_*> function creates a request. which is a C data structure not
134directly visible to Perl.
135
136If called in non-void context, every request function returns a Perl
137object representing the request. In void context, nothing is returned,
138which saves a bit of memory.
139
140The perl object is a fairly standard ref-to-hash object. The hash contents
141are not used by IO::AIO so you are free to store anything you like in it.
142
143During their existance, aio requests travel through the following states,
144in order:
145
146=over 4
147
148=item ready
149
150Immediately after a request is created it is put into the ready state,
151waiting for a thread to execute it.
152
153=item execute
154
155A thread has accepted the request for processing and is currently
156executing it (e.g. blocking in read).
157
158=item pending
159
160The request has been executed and is waiting for result processing.
161
162While request submission and execution is fully asynchronous, result
163processing is not and relies on the perl interpreter calling C<poll_cb>
164(or another function with the same effect).
165
166=item result
167
168The request results are processed synchronously by C<poll_cb>.
169
170The C<poll_cb> function will process all outstanding aio requests by
171calling their callbacks, freeing memory associated with them and managing
172any groups they are contained in.
173
174=item done
175
176Request has reached the end of its lifetime and holds no resources anymore
177(except possibly for the Perl object, but its connection to the actual
178aio request is severed and calling its methods will either do nothing or
179result in a runtime error).
49 180
50=cut 181=cut
51 182
52package IO::AIO; 183package IO::AIO;
53 184
185no warnings;
186use strict 'vars';
187
54use base 'Exporter'; 188use base 'Exporter';
55 189
56use Fcntl ();
57
58BEGIN { 190BEGIN {
59 $VERSION = 0.2; 191 our $VERSION = '2.1';
60 192
61 @EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink 193 our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
62 aio_fsync aio_fdatasync aio_readahead); 194 aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
63 @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs); 195 aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
196 aio_copy aio_group aio_nop aio_mknod);
197 our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
198 our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
199 min_parallel max_parallel max_idle
200 nreqs nready npending nthreads
201 max_poll_time max_poll_reqs);
202
203 @IO::AIO::GRP::ISA = 'IO::AIO::REQ';
64 204
65 require XSLoader; 205 require XSLoader;
66 XSLoader::load IO::AIO, $VERSION; 206 XSLoader::load ("IO::AIO", $VERSION);
67} 207}
68 208
69=head1 FUNCTIONS 209=head1 FUNCTIONS
70 210
71=head2 AIO FUNCTIONS 211=head2 AIO FUNCTIONS
72 212
73All the C<aio_*> calls are more or less thin wrappers around the syscall 213All the C<aio_*> calls are more or less thin wrappers around the syscall
74with the same name (sans C<aio_>). The arguments are similar or identical, 214with the same name (sans C<aio_>). The arguments are similar or identical,
75and they all accept an additional C<$callback> argument which must be 215and they all accept an additional (and optional) C<$callback> argument
76a code reference. This code reference will get called with the syscall 216which must be a code reference. This code reference will get called with
77return code (e.g. most syscalls return C<-1> on error, unlike perl, which 217the syscall return code (e.g. most syscalls return C<-1> on error, unlike
78usually delivers "false") as it's sole argument when the given syscall has 218perl, which usually delivers "false") as it's sole argument when the given
79been executed asynchronously. 219syscall has been executed asynchronously.
80 220
81All functions that expect a filehandle will also accept a file descriptor. 221All functions expecting a filehandle keep a copy of the filehandle
222internally until the request has finished.
82 223
224All requests return objects of type L<IO::AIO::REQ> that allow further
225manipulation of those requests while they are in-flight.
226
83The filenames you pass to these routines I<must> be absolute. The reason 227The pathnames you pass to these routines I<must> be absolute and
84is that at the time the request is being executed, the current working 228encoded in byte form. The reason for the former is that at the time the
85directory could have changed. Alternatively, you can make sure that you 229request is being executed, the current working directory could have
230changed. Alternatively, you can make sure that you never change the
86never change the current working directory. 231current working directory.
232
233To encode pathnames to byte form, either make sure you either: a)
234always pass in filenames you got from outside (command line, readdir
235etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode
236your pathnames to the locale (or other) encoding in effect in the user
237environment, d) use Glib::filename_from_unicode on unicode filenames or e)
238use something else.
87 239
88=over 4 240=over 4
89 241
242=item $prev_pri = aioreq_pri [$pri]
243
244Returns the priority value that would be used for the next request and, if
245C<$pri> is given, sets the priority for the next aio request.
246
247The default priority is C<0>, the minimum and maximum priorities are C<-4>
248and C<4>, respectively. Requests with higher priority will be serviced
249first.
250
251The priority will be reset to C<0> after each call to one of the C<aio_*>
252functions.
253
254Example: open a file with low priority, then read something from it with
255higher priority so the read request is serviced before other low priority
256open requests (potentially spamming the cache):
257
258 aioreq_pri -3;
259 aio_open ..., sub {
260 return unless $_[0];
261
262 aioreq_pri -2;
263 aio_read $_[0], ..., sub {
264 ...
265 };
266 };
267
268=item aioreq_nice $pri_adjust
269
270Similar to C<aioreq_pri>, but subtracts the given value from the current
271priority, so effects are cumulative.
272
90=item aio_open $pathname, $flags, $mode, $callback 273=item aio_open $pathname, $flags, $mode, $callback->($fh)
91 274
92Asynchronously open or create a file and call the callback with a newly 275Asynchronously open or create a file and call the callback with a newly
93created filehandle for the file. 276created filehandle for the file.
94 277
95The pathname passed to C<aio_open> must be absolute. See API NOTES, above, 278The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
96for an explanation. 279for an explanation.
97 280
98The C<$mode> argument is a bitmask. See the C<Fcntl> module for a 281The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
99list. They are the same as used in C<sysopen>. 282list. They are the same as used by C<sysopen>.
283
284Likewise, C<$mode> specifies the mode of the newly created file, if it
285didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
286except that it is mandatory (i.e. use C<0> if you don't create new files,
287and C<0666> or C<0777> if you do).
100 288
101Example: 289Example:
102 290
103 aio_open "/etc/passwd", O_RDONLY, 0, sub { 291 aio_open "/etc/passwd", O_RDONLY, 0, sub {
104 if ($_[0]) { 292 if ($_[0]) {
107 } else { 295 } else {
108 die "open failed: $!\n"; 296 die "open failed: $!\n";
109 } 297 }
110 }; 298 };
111 299
112=item aio_close $fh, $callback 300=item aio_close $fh, $callback->($status)
113 301
114Asynchronously close a file and call the callback with the result 302Asynchronously close a file and call the callback with the result
115code. I<WARNING:> although accepted, you should not pass in a perl 303code. I<WARNING:> although accepted, you should not pass in a perl
116filehandle here, as perl will likely close the file descriptor itself when 304filehandle here, as perl will likely close the file descriptor another
117the filehandle is destroyed. Normally, you can safely call perls C<close> 305time when the filehandle is destroyed. Normally, you can safely call perls
118or just let filehandles go out of scope. 306C<close> or just let filehandles go out of scope.
119 307
308This is supposed to be a bug in the API, so that might change. It's
309therefore best to avoid this function.
310
120=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback 311=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
121 312
122=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback 313=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
123 314
124Reads or writes C<length> bytes from the specified C<fh> and C<offset> 315Reads or writes C<length> bytes from the specified C<fh> and C<offset>
125into the scalar given by C<data> and offset C<dataoffset> and calls the 316into the scalar given by C<data> and offset C<dataoffset> and calls the
126callback without the actual number of bytes read (or -1 on error, just 317callback without the actual number of bytes read (or -1 on error, just
127like the syscall). 318like the syscall).
128 319
320The C<$data> scalar I<MUST NOT> be modified in any way while the request
321is outstanding. Modifying it can result in segfaults or WW3 (if the
322necessary/optional hardware is installed).
323
129Example: Read 15 bytes at offset 7 into scalar C<$buffer>, strating at 324Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
130offset C<0> within the scalar: 325offset C<0> within the scalar:
131 326
132 aio_read $fh, 7, 15, $buffer, 0, sub { 327 aio_read $fh, 7, 15, $buffer, 0, sub {
133 $_[0] > 0 or die "read error: $!"; 328 $_[0] > 0 or die "read error: $!";
134 print "read $_[0] bytes: <$buffer>\n"; 329 print "read $_[0] bytes: <$buffer>\n";
135 }; 330 };
136 331
332=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
333
334Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
335reading at byte offset C<$in_offset>, and starts writing at the current
336file offset of C<$out_fh>. Because of that, it is not safe to issue more
337than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
338other.
339
340This call tries to make use of a native C<sendfile> syscall to provide
341zero-copy operation. For this to work, C<$out_fh> should refer to a
342socket, and C<$in_fh> should refer to mmap'able file.
343
344If the native sendfile call fails or is not implemented, it will be
345emulated, so you can call C<aio_sendfile> on any type of filehandle
346regardless of the limitations of the operating system.
347
348Please note, however, that C<aio_sendfile> can read more bytes from
349C<$in_fh> than are written, and there is no way to find out how many
350bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
351provides the number of bytes written to C<$out_fh>. Only if the result
352value equals C<$length> one can assume that C<$length> bytes have been
353read.
354
137=item aio_readahead $fh,$offset,$length, $callback 355=item aio_readahead $fh,$offset,$length, $callback->($retval)
138 356
139Asynchronously reads the specified byte range into the page cache, using
140the C<readahead> syscall. If that syscall doesn't exist the status will be
141C<-1> and C<$!> is set to ENOSYS.
142
143readahead() populates the page cache with data from a file so that 357C<aio_readahead> populates the page cache with data from a file so that
144subsequent reads from that file will not block on disk I/O. The C<$offset> 358subsequent reads from that file will not block on disk I/O. The C<$offset>
145argument specifies the starting point from which data is to be read and 359argument specifies the starting point from which data is to be read and
146C<$length> specifies the number of bytes to be read. I/O is performed in 360C<$length> specifies the number of bytes to be read. I/O is performed in
147whole pages, so that offset is effectively rounded down to a page boundary 361whole pages, so that offset is effectively rounded down to a page boundary
148and bytes are read up to the next page boundary greater than or equal to 362and bytes are read up to the next page boundary greater than or equal to
149(off-set+length). aio_readahead() does not read beyond the end of the 363(off-set+length). C<aio_readahead> does not read beyond the end of the
150file. The current file offset of the file is left unchanged. 364file. The current file offset of the file is left unchanged.
151 365
366If that syscall doesn't exist (likely if your OS isn't Linux) it will be
367emulated by simply reading the data, which would have a similar effect.
368
152=item aio_stat $fh_or_path, $callback 369=item aio_stat $fh_or_path, $callback->($status)
153 370
154=item aio_lstat $fh, $callback 371=item aio_lstat $fh, $callback->($status)
155 372
156Works like perl's C<stat> or C<lstat> in void context. The callback will 373Works like perl's C<stat> or C<lstat> in void context. The callback will
157be called after the stat and the results will be available using C<stat _> 374be called after the stat and the results will be available using C<stat _>
158or C<-s _> etc... 375or C<-s _> etc...
159 376
169 aio_stat "/etc/passwd", sub { 386 aio_stat "/etc/passwd", sub {
170 $_[0] and die "stat failed: $!"; 387 $_[0] and die "stat failed: $!";
171 print "size is ", -s _, "\n"; 388 print "size is ", -s _, "\n";
172 }; 389 };
173 390
174=item aio_unlink $pathname, $callback 391=item aio_unlink $pathname, $callback->($status)
175 392
176Asynchronously unlink (delete) a file and call the callback with the 393Asynchronously unlink (delete) a file and call the callback with the
177result code. 394result code.
178 395
396=item aio_mknod $path, $mode, $dev, $callback->($status)
397
398[EXPERIMENTAL]
399
400Asynchronously create a device node (or fifo). See mknod(2).
401
402The only (POSIX-) portable way of calling this function is:
403
404 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
405
406=item aio_link $srcpath, $dstpath, $callback->($status)
407
408Asynchronously create a new link to the existing object at C<$srcpath> at
409the path C<$dstpath> and call the callback with the result code.
410
411=item aio_symlink $srcpath, $dstpath, $callback->($status)
412
413Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
414the path C<$dstpath> and call the callback with the result code.
415
416=item aio_rename $srcpath, $dstpath, $callback->($status)
417
418Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
419rename(2) and call the callback with the result code.
420
421=item aio_rmdir $pathname, $callback->($status)
422
423Asynchronously rmdir (delete) a directory and call the callback with the
424result code.
425
426=item aio_readdir $pathname, $callback->($entries)
427
428Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
429directory (i.e. opendir + readdir + closedir). The entries will not be
430sorted, and will B<NOT> include the C<.> and C<..> entries.
431
432The callback a single argument which is either C<undef> or an array-ref
433with the filenames.
434
435=item aio_copy $srcpath, $dstpath, $callback->($status)
436
437Try to copy the I<file> (directories not supported as either source or
438destination) from C<$srcpath> to C<$dstpath> and call the callback with
439the C<0> (error) or C<-1> ok.
440
441This is a composite request that it creates the destination file with
442mode 0200 and copies the contents of the source file into it using
443C<aio_sendfile>, followed by restoring atime, mtime, access mode and
444uid/gid, in that order.
445
446If an error occurs, the partial destination file will be unlinked, if
447possible, except when setting atime, mtime, access mode and uid/gid, where
448errors are being ignored.
449
450=cut
451
452sub aio_copy($$;$) {
453 my ($src, $dst, $cb) = @_;
454
455 my $pri = aioreq_pri;
456 my $grp = aio_group $cb;
457
458 aioreq_pri $pri;
459 add $grp aio_open $src, O_RDONLY, 0, sub {
460 if (my $src_fh = $_[0]) {
461 my @stat = stat $src_fh;
462
463 aioreq_pri $pri;
464 add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
465 if (my $dst_fh = $_[0]) {
466 aioreq_pri $pri;
467 add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
468 if ($_[0] == $stat[7]) {
469 $grp->result (0);
470 close $src_fh;
471
472 # those should not normally block. should. should.
473 utime $stat[8], $stat[9], $dst;
474 chmod $stat[2] & 07777, $dst_fh;
475 chown $stat[4], $stat[5], $dst_fh;
476 close $dst_fh;
477 } else {
478 $grp->result (-1);
479 close $src_fh;
480 close $dst_fh;
481
482 aioreq $pri;
483 add $grp aio_unlink $dst;
484 }
485 };
486 } else {
487 $grp->result (-1);
488 }
489 },
490
491 } else {
492 $grp->result (-1);
493 }
494 };
495
496 $grp
497}
498
499=item aio_move $srcpath, $dstpath, $callback->($status)
500
501Try to move the I<file> (directories not supported as either source or
502destination) from C<$srcpath> to C<$dstpath> and call the callback with
503the C<0> (error) or C<-1> ok.
504
505This is a composite request that tries to rename(2) the file first. If
506rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
507that is successful, unlinking the C<$srcpath>.
508
509=cut
510
511sub aio_move($$;$) {
512 my ($src, $dst, $cb) = @_;
513
514 my $pri = aioreq_pri;
515 my $grp = aio_group $cb;
516
517 aioreq_pri $pri;
518 add $grp aio_rename $src, $dst, sub {
519 if ($_[0] && $! == EXDEV) {
520 aioreq_pri $pri;
521 add $grp aio_copy $src, $dst, sub {
522 $grp->result ($_[0]);
523
524 if (!$_[0]) {
525 aioreq_pri $pri;
526 add $grp aio_unlink $src;
527 }
528 };
529 } else {
530 $grp->result ($_[0]);
531 }
532 };
533
534 $grp
535}
536
537=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
538
539Scans a directory (similar to C<aio_readdir>) but additionally tries to
540efficiently separate the entries of directory C<$path> into two sets of
541names, directories you can recurse into (directories), and ones you cannot
542recurse into (everything else, including symlinks to directories).
543
544C<aio_scandir> is a composite request that creates of many sub requests_
545C<$maxreq> specifies the maximum number of outstanding aio requests that
546this function generates. If it is C<< <= 0 >>, then a suitable default
547will be chosen (currently 4).
548
549On error, the callback is called without arguments, otherwise it receives
550two array-refs with path-relative entry names.
551
552Example:
553
554 aio_scandir $dir, 0, sub {
555 my ($dirs, $nondirs) = @_;
556 print "real directories: @$dirs\n";
557 print "everything else: @$nondirs\n";
558 };
559
560Implementation notes.
561
562The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
563
564After reading the directory, the modification time, size etc. of the
565directory before and after the readdir is checked, and if they match (and
566isn't the current time), the link count will be used to decide how many
567entries are directories (if >= 2). Otherwise, no knowledge of the number
568of subdirectories will be assumed.
569
570Then entries will be sorted into likely directories (everything without
571a non-initial dot currently) and likely non-directories (everything
572else). Then every entry plus an appended C</.> will be C<stat>'ed,
573likely directories first. If that succeeds, it assumes that the entry
574is a directory or a symlink to directory (which will be checked
575seperately). This is often faster than stat'ing the entry itself because
576filesystems might detect the type of the entry without reading the inode
577data (e.g. ext2fs filetype feature).
578
579If the known number of directories (link count - 2) has been reached, the
580rest of the entries is assumed to be non-directories.
581
582This only works with certainty on POSIX (= UNIX) filesystems, which
583fortunately are the vast majority of filesystems around.
584
585It will also likely work on non-POSIX filesystems with reduced efficiency
586as those tend to return 0 or 1 as link counts, which disables the
587directory counting heuristic.
588
589=cut
590
591sub aio_scandir($$$) {
592 my ($path, $maxreq, $cb) = @_;
593
594 my $pri = aioreq_pri;
595
596 my $grp = aio_group $cb;
597
598 $maxreq = 4 if $maxreq <= 0;
599
600 # stat once
601 aioreq_pri $pri;
602 add $grp aio_stat $path, sub {
603 return $grp->result () if $_[0];
604 my $now = time;
605 my $hash1 = join ":", (stat _)[0,1,3,7,9];
606
607 # read the directory entries
608 aioreq_pri $pri;
609 add $grp aio_readdir $path, sub {
610 my $entries = shift
611 or return $grp->result ();
612
613 # stat the dir another time
614 aioreq_pri $pri;
615 add $grp aio_stat $path, sub {
616 my $hash2 = join ":", (stat _)[0,1,3,7,9];
617
618 my $ndirs;
619
620 # take the slow route if anything looks fishy
621 if ($hash1 ne $hash2 or (stat _)[9] == $now) {
622 $ndirs = -1;
623 } else {
624 # if nlink == 2, we are finished
625 # on non-posix-fs's, we rely on nlink < 2
626 $ndirs = (stat _)[3] - 2
627 or return $grp->result ([], $entries);
628 }
629
630 # sort into likely dirs and likely nondirs
631 # dirs == files without ".", short entries first
632 $entries = [map $_->[0],
633 sort { $b->[1] cmp $a->[1] }
634 map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
635 @$entries];
636
637 my (@dirs, @nondirs);
638
639 my $statgrp = add $grp aio_group sub {
640 $grp->result (\@dirs, \@nondirs);
641 };
642
643 limit $statgrp $maxreq;
644 feed $statgrp sub {
645 return unless @$entries;
646 my $entry = pop @$entries;
647
648 aioreq_pri $pri;
649 add $statgrp aio_stat "$path/$entry/.", sub {
650 if ($_[0] < 0) {
651 push @nondirs, $entry;
652 } else {
653 # need to check for real directory
654 aioreq_pri $pri;
655 add $statgrp aio_lstat "$path/$entry", sub {
656 if (-d _) {
657 push @dirs, $entry;
658
659 unless (--$ndirs) {
660 push @nondirs, @$entries;
661 feed $statgrp;
662 }
663 } else {
664 push @nondirs, $entry;
665 }
666 }
667 }
668 };
669 };
670 };
671 };
672 };
673
674 $grp
675}
676
179=item aio_fsync $fh, $callback 677=item aio_fsync $fh, $callback->($status)
180 678
181Asynchronously call fsync on the given filehandle and call the callback 679Asynchronously call fsync on the given filehandle and call the callback
182with the fsync result code. 680with the fsync result code.
183 681
184=item aio_fdatasync $fh, $callback 682=item aio_fdatasync $fh, $callback->($status)
185 683
186Asynchronously call fdatasync on the given filehandle and call the 684Asynchronously call fdatasync on the given filehandle and call the
187callback with the fdatasync result code. 685callback with the fdatasync result code.
188 686
687If this call isn't available because your OS lacks it or it couldn't be
688detected, it will be emulated by calling C<fsync> instead.
689
690=item aio_group $callback->(...)
691
692This is a very special aio request: Instead of doing something, it is a
693container for other aio requests, which is useful if you want to bundle
694many requests into a single, composite, request with a definite callback
695and the ability to cancel the whole request with its subrequests.
696
697Returns an object of class L<IO::AIO::GRP>. See its documentation below
698for more info.
699
700Example:
701
702 my $grp = aio_group sub {
703 print "all stats done\n";
704 };
705
706 add $grp
707 (aio_stat ...),
708 (aio_stat ...),
709 ...;
710
711=item aio_nop $callback->()
712
713This is a special request - it does nothing in itself and is only used for
714side effects, such as when you want to add a dummy request to a group so
715that finishing the requests in the group depends on executing the given
716code.
717
718While this request does nothing, it still goes through the execution
719phase and still requires a worker thread. Thus, the callback will not
720be executed immediately but only after other requests in the queue have
721entered their execution phase. This can be used to measure request
722latency.
723
724=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
725
726Mainly used for debugging and benchmarking, this aio request puts one of
727the request workers to sleep for the given time.
728
729While it is theoretically handy to have simple I/O scheduling requests
730like sleep and file handle readable/writable, the overhead this creates is
731immense (it blocks a thread for a long time) so do not use this function
732except to put your application under artificial I/O pressure.
733
189=back 734=back
190 735
736=head2 IO::AIO::REQ CLASS
737
738All non-aggregate C<aio_*> functions return an object of this class when
739called in non-void context.
740
741=over 4
742
743=item cancel $req
744
745Cancels the request, if possible. Has the effect of skipping execution
746when entering the B<execute> state and skipping calling the callback when
747entering the the B<result> state, but will leave the request otherwise
748untouched. That means that requests that currently execute will not be
749stopped and resources held by the request will not be freed prematurely.
750
751=item cb $req $callback->(...)
752
753Replace (or simply set) the callback registered to the request.
754
755=back
756
757=head2 IO::AIO::GRP CLASS
758
759This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
760objects of this class, too.
761
762A IO::AIO::GRP object is a special request that can contain multiple other
763aio requests.
764
765You create one by calling the C<aio_group> constructing function with a
766callback that will be called when all contained requests have entered the
767C<done> state:
768
769 my $grp = aio_group sub {
770 print "all requests are done\n";
771 };
772
773You add requests by calling the C<add> method with one or more
774C<IO::AIO::REQ> objects:
775
776 $grp->add (aio_unlink "...");
777
778 add $grp aio_stat "...", sub {
779 $_[0] or return $grp->result ("error");
780
781 # add another request dynamically, if first succeeded
782 add $grp aio_open "...", sub {
783 $grp->result ("ok");
784 };
785 };
786
787This makes it very easy to create composite requests (see the source of
788C<aio_move> for an application) that work and feel like simple requests.
789
790=over 4
791
792=item * The IO::AIO::GRP objects will be cleaned up during calls to
793C<IO::AIO::poll_cb>, just like any other request.
794
795=item * They can be canceled like any other request. Canceling will cancel not
796only the request itself, but also all requests it contains.
797
798=item * They can also can also be added to other IO::AIO::GRP objects.
799
800=item * You must not add requests to a group from within the group callback (or
801any later time).
802
803=back
804
805Their lifetime, simplified, looks like this: when they are empty, they
806will finish very quickly. If they contain only requests that are in the
807C<done> state, they will also finish. Otherwise they will continue to
808exist.
809
810That means after creating a group you have some time to add requests. And
811in the callbacks of those requests, you can add further requests to the
812group. And only when all those requests have finished will the the group
813itself finish.
814
815=over 4
816
817=item add $grp ...
818
819=item $grp->add (...)
820
821Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
822be added, including other groups, as long as you do not create circular
823dependencies.
824
825Returns all its arguments.
826
827=item $grp->cancel_subs
828
829Cancel all subrequests and clears any feeder, but not the group request
830itself. Useful when you queued a lot of events but got a result early.
831
832=item $grp->result (...)
833
834Set the result value(s) that will be passed to the group callback when all
835subrequests have finished and set thre groups errno to the current value
836of errno (just like calling C<errno> without an error number). By default,
837no argument will be passed and errno is zero.
838
839=item $grp->errno ([$errno])
840
841Sets the group errno value to C<$errno>, or the current value of errno
842when the argument is missing.
843
844Every aio request has an associated errno value that is restored when
845the callback is invoked. This method lets you change this value from its
846default (0).
847
848Calling C<result> will also set errno, so make sure you either set C<$!>
849before the call to C<result>, or call c<errno> after it.
850
851=item feed $grp $callback->($grp)
852
853Sets a feeder/generator on this group: every group can have an attached
854generator that generates requests if idle. The idea behind this is that,
855although you could just queue as many requests as you want in a group,
856this might starve other requests for a potentially long time. For
857example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
858requests, delaying any later requests for a long time.
859
860To avoid this, and allow incremental generation of requests, you can
861instead a group and set a feeder on it that generates those requests. The
862feed callback will be called whenever there are few enough (see C<limit>,
863below) requests active in the group itself and is expected to queue more
864requests.
865
866The feed callback can queue as many requests as it likes (i.e. C<add> does
867not impose any limits).
868
869If the feed does not queue more requests when called, it will be
870automatically removed from the group.
871
872If the feed limit is C<0>, it will be set to C<2> automatically.
873
874Example:
875
876 # stat all files in @files, but only ever use four aio requests concurrently:
877
878 my $grp = aio_group sub { print "finished\n" };
879 limit $grp 4;
880 feed $grp sub {
881 my $file = pop @files
882 or return;
883
884 add $grp aio_stat $file, sub { ... };
885 };
886
887=item limit $grp $num
888
889Sets the feeder limit for the group: The feeder will be called whenever
890the group contains less than this many requests.
891
892Setting the limit to C<0> will pause the feeding process.
893
894=back
895
191=head2 SUPPORT FUNCTIONS 896=head2 SUPPORT FUNCTIONS
192 897
898=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
899
193=over 4 900=over 4
194 901
195=item $fileno = IO::AIO::poll_fileno 902=item $fileno = IO::AIO::poll_fileno
196 903
197Return the I<request result pipe filehandle>. This filehandle must be 904Return the I<request result pipe file descriptor>. This filehandle must be
198polled for reading by some mechanism outside this module (e.g. Event 905polled for reading by some mechanism outside this module (e.g. Event or
199or select, see below). If the pipe becomes readable you have to call 906select, see below or the SYNOPSIS). If the pipe becomes readable you have
200C<poll_cb> to check the results. 907to call C<poll_cb> to check the results.
201 908
202See C<poll_cb> for an example. 909See C<poll_cb> for an example.
203 910
204=item IO::AIO::poll_cb 911=item IO::AIO::poll_cb
205 912
206Process all outstanding events on the result pipe. You have to call this 913Process some outstanding events on the result pipe. You have to call this
207regularly. Returns the number of events processed. Returns immediately 914regularly. Returns the number of events processed. Returns immediately
208when no events are outstanding. 915when no events are outstanding. The amount of events processed depends on
916the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
209 917
210You can use Event to multiplex, e.g.: 918If not all requests were processed for whatever reason, the filehandle
919will still be ready when C<poll_cb> returns.
920
921Example: Install an Event watcher that automatically calls
922IO::AIO::poll_cb with high priority:
211 923
212 Event->io (fd => IO::AIO::poll_fileno, 924 Event->io (fd => IO::AIO::poll_fileno,
213 poll => 'r', async => 1, 925 poll => 'r', async => 1,
214 cb => \&IO::AIO::poll_cb); 926 cb => \&IO::AIO::poll_cb);
215 927
928=item IO::AIO::max_poll_reqs $nreqs
929
930=item IO::AIO::max_poll_time $seconds
931
932These set the maximum number of requests (default C<0>, meaning infinity)
933that are being processed by C<IO::AIO::poll_cb> in one call, respectively
934the maximum amount of time (default C<0>, meaning infinity) spent in
935C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
936of time C<poll_cb> is allowed to use).
937
938Setting these is useful if you want to ensure some level of
939interactiveness when perl is not fast enough to process all requests in
940time.
941
942For interactive programs, values such as C<0.01> to C<0.1> should be fine.
943
944Example: Install an Event watcher that automatically calls
945IO::AIO::poll_some with low priority, to ensure that other parts of the
946program get the CPU sometimes even under high AIO load.
947
948 # try not to spend much more than 0.1s in poll_cb
949 IO::AIO::max_poll_time 0.1;
950
951 # use a low priority so other tasks have priority
952 Event->io (fd => IO::AIO::poll_fileno,
953 poll => 'r', nice => 1,
954 cb => &IO::AIO::poll_cb);
955
216=item IO::AIO::poll_wait 956=item IO::AIO::poll_wait
217 957
218Wait till the result filehandle becomes ready for reading (simply does a 958Wait till the result filehandle becomes ready for reading (simply does a
219select on the filehandle. This is useful if you want to synchronously wait 959C<select> on the filehandle. This is useful if you want to synchronously
220for some requests to finish). 960wait for some requests to finish).
221 961
222See C<nreqs> for an example. 962See C<nreqs> for an example.
223 963
964=item IO::AIO::poll
965
966Waits until some requests have been handled.
967
968Strictly equivalent to:
969
970 IO::AIO::poll_wait, IO::AIO::poll_cb
971 if IO::AIO::nreqs;
972
224=item IO::AIO::nreqs 973=item IO::AIO::flush
225 974
226Returns the number of requests currently outstanding. 975Wait till all outstanding AIO requests have been handled.
227 976
228Example: wait till there are no outstanding requests anymore: 977Strictly equivalent to:
229 978
230 IO::AIO::poll_wait, IO::AIO::poll_cb 979 IO::AIO::poll_wait, IO::AIO::poll_cb
231 while IO::AIO::nreqs; 980 while IO::AIO::nreqs;
232 981
982=head3 CONTROLLING THE NUMBER OF THREADS
983
233=item IO::AIO::min_parallel $nthreads 984=item IO::AIO::min_parallel $nthreads
234 985
235Set the minimum number of AIO threads to C<$nthreads>. The default is 986Set the minimum number of AIO threads to C<$nthreads>. The current
236C<1>, which means a single asynchronous operation can be done at one time 987default is C<8>, which means eight asynchronous operations can execute
237(the number of outstanding operations, however, is unlimited). 988concurrently at any one time (the number of outstanding requests,
989however, is unlimited).
238 990
991IO::AIO starts threads only on demand, when an AIO request is queued and
992no free thread exists. Please note that queueing up a hundred requests can
993create demand for a hundred threads, even if it turns out that everything
994is in the cache and could have been processed faster by a single thread.
995
239It is recommended to keep the number of threads low, as some Linux 996It is recommended to keep the number of threads relatively low, as some
240kernel versions will scale negatively with the number of threads (higher 997Linux kernel versions will scale negatively with the number of threads
241parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32 998(higher parallelity => MUCH higher latency). With current Linux 2.6
242threads should be fine. 999versions, 4-32 threads should be fine.
243 1000
244Under normal circumstances you don't need to call this function, as this 1001Under most circumstances you don't need to call this function, as the
245module automatically starts some threads (the exact number might change, 1002module selects a default that is suitable for low to moderate load.
246and is currently 4).
247 1003
248=item IO::AIO::max_parallel $nthreads 1004=item IO::AIO::max_parallel $nthreads
249 1005
250Sets the maximum number of AIO threads to C<$nthreads>. If more than 1006Sets the maximum number of AIO threads to C<$nthreads>. If more than the
251the specified number of threads are currently running, kill them. This 1007specified number of threads are currently running, this function kills
252function blocks until the limit is reached. 1008them. This function blocks until the limit is reached.
1009
1010While C<$nthreads> are zero, aio requests get queued but not executed
1011until the number of threads has been increased again.
253 1012
254This module automatically runs C<max_parallel 0> at program end, to ensure 1013This module automatically runs C<max_parallel 0> at program end, to ensure
255that all threads are killed and that there are no outstanding requests. 1014that all threads are killed and that there are no outstanding requests.
256 1015
257Under normal circumstances you don't need to call this function. 1016Under normal circumstances you don't need to call this function.
258 1017
1018=item IO::AIO::max_idle $nthreads
1019
1020Limit the number of threads (default: 4) that are allowed to idle (i.e.,
1021threads that did not get a request to process within 10 seconds). That
1022means if a thread becomes idle while C<$nthreads> other threads are also
1023idle, it will free its resources and exit.
1024
1025This is useful when you allow a large number of threads (e.g. 100 or 1000)
1026to allow for extremely high load situations, but want to free resources
1027under normal circumstances (1000 threads can easily consume 30MB of RAM).
1028
1029The default is probably ok in most situations, especially if thread
1030creation is fast. If thread creation is very slow on your system you might
1031want to use larger values.
1032
259=item $oldnreqs = IO::AIO::max_outstanding $nreqs 1033=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
1034
1035This is a very bad function to use in interactive programs because it
1036blocks, and a bad way to reduce concurrency because it is inexact: Better
1037use an C<aio_group> together with a feed callback.
260 1038
261Sets the maximum number of outstanding requests to C<$nreqs>. If you 1039Sets the maximum number of outstanding requests to C<$nreqs>. If you
262try to queue up more than this number of requests, the caller will block until 1040to queue up more than this number of requests, the next call to the
263some requests have been handled. 1041C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1042function will block until the limit is no longer exceeded.
264 1043
265The default is very large, so normally there is no practical limit. If you 1044The default value is very large, so there is no practical limit on the
266queue up many requests in a loop it it often improves speed if you set 1045number of outstanding requests.
267this to a relatively low number, such as C<100>.
268 1046
269Under normal circumstances you don't need to call this function. 1047You can still queue as many requests as you want. Therefore,
1048C<max_oustsanding> is mainly useful in simple scripts (with low values) or
1049as a stop gap to shield against fatal memory overflow (with large values).
1050
1051=head3 STATISTICAL INFORMATION
1052
1053=item IO::AIO::nreqs
1054
1055Returns the number of requests currently in the ready, execute or pending
1056states (i.e. for which their callback has not been invoked yet).
1057
1058Example: wait till there are no outstanding requests anymore:
1059
1060 IO::AIO::poll_wait, IO::AIO::poll_cb
1061 while IO::AIO::nreqs;
1062
1063=item IO::AIO::nready
1064
1065Returns the number of requests currently in the ready state (not yet
1066executed).
1067
1068=item IO::AIO::npending
1069
1070Returns the number of requests currently in the pending state (executed,
1071but not yet processed by poll_cb).
270 1072
271=back 1073=back
272 1074
273=cut 1075=cut
274 1076
275# support function to convert a fd into a perl filehandle 1077# support function to convert a fd into a perl filehandle
276sub _fd2fh { 1078sub _fd2fh {
277 return undef if $_[0] < 0; 1079 return undef if $_[0] < 0;
278 1080
279 # try to be perl5.6-compatible 1081 # try to generate nice filehandles
280 local *AIO_FH; 1082 my $sym = "IO::AIO::fd#$_[0]";
281 open AIO_FH, "+<&=$_[0]" 1083 local *$sym;
1084
1085 open *$sym, "+<&=$_[0]" # usually works under any unix
1086 or open *$sym, "<&=$_[0]" # cygwin needs this
1087 or open *$sym, ">&=$_[0]" # or this
282 or return undef; 1088 or return undef;
283 1089
284 *AIO_FH 1090 *$sym
285} 1091}
286 1092
287min_parallel 4; 1093min_parallel 8;
288 1094
289END { 1095END {
290 max_parallel 0; 1096 min_parallel 1;
291} 1097 flush;
1098};
292 1099
2931; 11001;
294 1101
1102=head2 FORK BEHAVIOUR
1103
1104This module should do "the right thing" when the process using it forks:
1105
1106Before the fork, IO::AIO enters a quiescent state where no requests
1107can be added in other threads and no results will be processed. After
1108the fork the parent simply leaves the quiescent state and continues
1109request/result processing, while the child frees the request/result queue
1110(so that the requests started before the fork will only be handled in the
1111parent). Threads will be started on demand until the limit set in the
1112parent process has been reached again.
1113
1114In short: the parent will, after a short pause, continue as if fork had
1115not been called, while the child will act as if IO::AIO has not been used
1116yet.
1117
1118=head2 MEMORY USAGE
1119
1120Per-request usage:
1121
1122Each aio request uses - depending on your architecture - around 100-200
1123bytes of memory. In addition, stat requests need a stat buffer (possibly
1124a few hundred bytes), readdir requires a result buffer and so on. Perl
1125scalars and other data passed into aio requests will also be locked and
1126will consume memory till the request has entered the done state.
1127
1128This is now awfully much, so queuing lots of requests is not usually a
1129problem.
1130
1131Per-thread usage:
1132
1133In the execution phase, some aio requests require more memory for
1134temporary buffers, and each thread requires a stack and other data
1135structures (usually around 16k-128k, depending on the OS).
1136
1137=head1 KNOWN BUGS
1138
1139Known bugs will be fixed in the next release.
1140
295=head1 SEE ALSO 1141=head1 SEE ALSO
296 1142
297L<Coro>, L<Linux::AIO>. 1143L<Coro::AIO>.
298 1144
299=head1 AUTHOR 1145=head1 AUTHOR
300 1146
301 Marc Lehmann <schmorp@schmorp.de> 1147 Marc Lehmann <schmorp@schmorp.de>
302 http://home.schmorp.de/ 1148 http://home.schmorp.de/

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