1 |
=head1 NAME |
2 |
|
3 |
IO::AIO - Asynchronous Input/Output |
4 |
|
5 |
=head1 SYNOPSIS |
6 |
|
7 |
use IO::AIO; |
8 |
|
9 |
aio_open "/etc/passwd", O_RDONLY, 0, sub { |
10 |
my ($fh) = @_; |
11 |
... |
12 |
}; |
13 |
|
14 |
aio_unlink "/tmp/file", sub { }; |
15 |
|
16 |
aio_read $fh, 30000, 1024, $buffer, 0, sub { |
17 |
$_[0] > 0 or die "read error: $!"; |
18 |
}; |
19 |
|
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 |
35 |
Event->io (fd => IO::AIO::poll_fileno, |
36 |
poll => 'r', |
37 |
cb => \&IO::AIO::poll_cb); |
38 |
|
39 |
# Glib/Gtk2 integration |
40 |
add_watch Glib::IO IO::AIO::poll_fileno, |
41 |
in => sub { IO::AIO::poll_cb; 1 }; |
42 |
|
43 |
# Tk integration |
44 |
Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "", |
45 |
readable => \&IO::AIO::poll_cb); |
46 |
|
47 |
# Danga::Socket integration |
48 |
Danga::Socket->AddOtherFds (IO::AIO::poll_fileno => |
49 |
\&IO::AIO::poll_cb); |
50 |
|
51 |
=head1 DESCRIPTION |
52 |
|
53 |
This module implements asynchronous I/O using whatever means your |
54 |
operating system supports. |
55 |
|
56 |
Currently, a number of threads are started that execute your read/writes |
57 |
and signal their completion. You don't need thread support in perl, and |
58 |
the threads created by this module will not be visible to perl. In the |
59 |
future, this module might make use of the native aio functions available |
60 |
on many operating systems. However, they are often not well-supported |
61 |
(Linux doesn't allow them on normal files currently, for example), |
62 |
and they would only support aio_read and aio_write, so the remaining |
63 |
functionality would have to be implemented using threads anyway. |
64 |
|
65 |
Although the module will work with in the presence of other threads, |
66 |
it is currently not reentrant in any way, so use appropriate locking |
67 |
yourself, always call C<poll_cb> from within the same thread, or never |
68 |
call C<poll_cb> (or other C<aio_> functions) recursively. |
69 |
|
70 |
=cut |
71 |
|
72 |
package IO::AIO; |
73 |
|
74 |
no warnings; |
75 |
use strict 'vars'; |
76 |
|
77 |
use base 'Exporter'; |
78 |
|
79 |
BEGIN { |
80 |
our $VERSION = '2.0'; |
81 |
|
82 |
our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat |
83 |
aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink |
84 |
aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move |
85 |
aio_group aio_nop); |
86 |
our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice)); |
87 |
our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush |
88 |
min_parallel max_parallel max_outstanding nreqs); |
89 |
|
90 |
@IO::AIO::GRP::ISA = 'IO::AIO::REQ'; |
91 |
|
92 |
require XSLoader; |
93 |
XSLoader::load ("IO::AIO", $VERSION); |
94 |
} |
95 |
|
96 |
=head1 FUNCTIONS |
97 |
|
98 |
=head2 AIO FUNCTIONS |
99 |
|
100 |
All the C<aio_*> calls are more or less thin wrappers around the syscall |
101 |
with the same name (sans C<aio_>). The arguments are similar or identical, |
102 |
and they all accept an additional (and optional) C<$callback> argument |
103 |
which must be a code reference. This code reference will get called with |
104 |
the syscall return code (e.g. most syscalls return C<-1> on error, unlike |
105 |
perl, which usually delivers "false") as it's sole argument when the given |
106 |
syscall has been executed asynchronously. |
107 |
|
108 |
All functions expecting a filehandle keep a copy of the filehandle |
109 |
internally until the request has finished. |
110 |
|
111 |
All requests return objects of type L<IO::AIO::REQ> that allow further |
112 |
manipulation of those requests while they are in-flight. |
113 |
|
114 |
The pathnames you pass to these routines I<must> be absolute and |
115 |
encoded in byte form. The reason for the former is that at the time the |
116 |
request is being executed, the current working directory could have |
117 |
changed. Alternatively, you can make sure that you never change the |
118 |
current working directory. |
119 |
|
120 |
To encode pathnames to byte form, either make sure you either: a) |
121 |
always pass in filenames you got from outside (command line, readdir |
122 |
etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode |
123 |
your pathnames to the locale (or other) encoding in effect in the user |
124 |
environment, d) use Glib::filename_from_unicode on unicode filenames or e) |
125 |
use something else. |
126 |
|
127 |
=over 4 |
128 |
|
129 |
=item aioreq_pri $pri |
130 |
|
131 |
Sets the priority for the next aio request. The default priority |
132 |
is C<0>, the minimum and maximum priorities are C<-4> and C<4>, |
133 |
respectively. Requests with higher priority will be serviced first. |
134 |
|
135 |
The priority will be reset to C<0> after each call to one of the C<aio_> |
136 |
functions. |
137 |
|
138 |
Example: open a file with low priority, then read something from it with |
139 |
higher priority so the read request is serviced before other low priority |
140 |
open requests (potentially spamming the cache): |
141 |
|
142 |
aioreq_pri -3; |
143 |
aio_open ..., sub { |
144 |
return unless $_[0]; |
145 |
|
146 |
aioreq_pri -2; |
147 |
aio_read $_[0], ..., sub { |
148 |
... |
149 |
}; |
150 |
}; |
151 |
|
152 |
=item aioreq_nice $pri_adjust |
153 |
|
154 |
Similar to C<aioreq_pri>, but subtracts the given value from the current |
155 |
priority, so effects are cumulative. |
156 |
|
157 |
=item aio_open $pathname, $flags, $mode, $callback->($fh) |
158 |
|
159 |
Asynchronously open or create a file and call the callback with a newly |
160 |
created filehandle for the file. |
161 |
|
162 |
The pathname passed to C<aio_open> must be absolute. See API NOTES, above, |
163 |
for an explanation. |
164 |
|
165 |
The C<$flags> argument is a bitmask. See the C<Fcntl> module for a |
166 |
list. They are the same as used by C<sysopen>. |
167 |
|
168 |
Likewise, C<$mode> specifies the mode of the newly created file, if it |
169 |
didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>, |
170 |
except that it is mandatory (i.e. use C<0> if you don't create new files, |
171 |
and C<0666> or C<0777> if you do). |
172 |
|
173 |
Example: |
174 |
|
175 |
aio_open "/etc/passwd", O_RDONLY, 0, sub { |
176 |
if ($_[0]) { |
177 |
print "open successful, fh is $_[0]\n"; |
178 |
... |
179 |
} else { |
180 |
die "open failed: $!\n"; |
181 |
} |
182 |
}; |
183 |
|
184 |
=item aio_close $fh, $callback->($status) |
185 |
|
186 |
Asynchronously close a file and call the callback with the result |
187 |
code. I<WARNING:> although accepted, you should not pass in a perl |
188 |
filehandle here, as perl will likely close the file descriptor another |
189 |
time when the filehandle is destroyed. Normally, you can safely call perls |
190 |
C<close> or just let filehandles go out of scope. |
191 |
|
192 |
This is supposed to be a bug in the API, so that might change. It's |
193 |
therefore best to avoid this function. |
194 |
|
195 |
=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) |
196 |
|
197 |
=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) |
198 |
|
199 |
Reads or writes C<length> bytes from the specified C<fh> and C<offset> |
200 |
into the scalar given by C<data> and offset C<dataoffset> and calls the |
201 |
callback without the actual number of bytes read (or -1 on error, just |
202 |
like the syscall). |
203 |
|
204 |
The C<$data> scalar I<MUST NOT> be modified in any way while the request |
205 |
is outstanding. Modifying it can result in segfaults or WW3 (if the |
206 |
necessary/optional hardware is installed). |
207 |
|
208 |
Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at |
209 |
offset C<0> within the scalar: |
210 |
|
211 |
aio_read $fh, 7, 15, $buffer, 0, sub { |
212 |
$_[0] > 0 or die "read error: $!"; |
213 |
print "read $_[0] bytes: <$buffer>\n"; |
214 |
}; |
215 |
|
216 |
=item aio_move $srcpath, $dstpath, $callback->($status) |
217 |
|
218 |
Try to move the I<file> (directories not supported as either source or |
219 |
destination) from C<$srcpath> to C<$dstpath> and call the callback with |
220 |
the C<0> (error) or C<-1> ok. |
221 |
|
222 |
This is a composite request that tries to rename(2) the file first. If |
223 |
rename files with C<EXDEV>, it creates the destination file with mode 0200 |
224 |
and copies the contents of the source file into it using C<aio_sendfile>, |
225 |
followed by restoring atime, mtime, access mode and uid/gid, in that |
226 |
order, and unlinking the C<$srcpath>. |
227 |
|
228 |
If an error occurs, the partial destination file will be unlinked, if |
229 |
possible, except when setting atime, mtime, access mode and uid/gid, where |
230 |
errors are being ignored. |
231 |
|
232 |
=cut |
233 |
|
234 |
sub aio_move($$$) { |
235 |
my ($src, $dst, $cb) = @_; |
236 |
|
237 |
my $grp = aio_group $cb; |
238 |
|
239 |
add $grp aio_rename $src, $dst, sub { |
240 |
if ($_[0] && $! == EXDEV) { |
241 |
add $grp aio_open $src, O_RDONLY, 0, sub { |
242 |
if (my $src_fh = $_[0]) { |
243 |
my @stat = stat $src_fh; |
244 |
|
245 |
add $grp aio_open $dst, O_WRONLY, 0200, sub { |
246 |
if (my $dst_fh = $_[0]) { |
247 |
add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub { |
248 |
close $src_fh; |
249 |
|
250 |
if ($_[0] == $stat[7]) { |
251 |
utime $stat[8], $stat[9], $dst; |
252 |
chmod $stat[2] & 07777, $dst_fh; |
253 |
chown $stat[4], $stat[5], $dst_fh; |
254 |
close $dst_fh; |
255 |
|
256 |
add $grp aio_unlink $src, sub { |
257 |
$grp->result ($_[0]); |
258 |
}; |
259 |
} else { |
260 |
my $errno = $!; |
261 |
add $grp aio_unlink $dst, sub { |
262 |
$! = $errno; |
263 |
$grp->result (-1); |
264 |
}; |
265 |
} |
266 |
}; |
267 |
} else { |
268 |
$grp->result (-1); |
269 |
} |
270 |
}, |
271 |
|
272 |
} else { |
273 |
$grp->result (-1); |
274 |
} |
275 |
}; |
276 |
} else { |
277 |
$grp->result ($_[0]); |
278 |
} |
279 |
}; |
280 |
|
281 |
$grp |
282 |
} |
283 |
|
284 |
=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) |
285 |
|
286 |
Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts |
287 |
reading at byte offset C<$in_offset>, and starts writing at the current |
288 |
file offset of C<$out_fh>. Because of that, it is not safe to issue more |
289 |
than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each |
290 |
other. |
291 |
|
292 |
This call tries to make use of a native C<sendfile> syscall to provide |
293 |
zero-copy operation. For this to work, C<$out_fh> should refer to a |
294 |
socket, and C<$in_fh> should refer to mmap'able file. |
295 |
|
296 |
If the native sendfile call fails or is not implemented, it will be |
297 |
emulated, so you can call C<aio_sendfile> on any type of filehandle |
298 |
regardless of the limitations of the operating system. |
299 |
|
300 |
Please note, however, that C<aio_sendfile> can read more bytes from |
301 |
C<$in_fh> than are written, and there is no way to find out how many |
302 |
bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only |
303 |
provides the number of bytes written to C<$out_fh>. Only if the result |
304 |
value equals C<$length> one can assume that C<$length> bytes have been |
305 |
read. |
306 |
|
307 |
=item aio_readahead $fh,$offset,$length, $callback->($retval) |
308 |
|
309 |
C<aio_readahead> populates the page cache with data from a file so that |
310 |
subsequent reads from that file will not block on disk I/O. The C<$offset> |
311 |
argument specifies the starting point from which data is to be read and |
312 |
C<$length> specifies the number of bytes to be read. I/O is performed in |
313 |
whole pages, so that offset is effectively rounded down to a page boundary |
314 |
and bytes are read up to the next page boundary greater than or equal to |
315 |
(off-set+length). C<aio_readahead> does not read beyond the end of the |
316 |
file. The current file offset of the file is left unchanged. |
317 |
|
318 |
If that syscall doesn't exist (likely if your OS isn't Linux) it will be |
319 |
emulated by simply reading the data, which would have a similar effect. |
320 |
|
321 |
=item aio_stat $fh_or_path, $callback->($status) |
322 |
|
323 |
=item aio_lstat $fh, $callback->($status) |
324 |
|
325 |
Works like perl's C<stat> or C<lstat> in void context. The callback will |
326 |
be called after the stat and the results will be available using C<stat _> |
327 |
or C<-s _> etc... |
328 |
|
329 |
The pathname passed to C<aio_stat> must be absolute. See API NOTES, above, |
330 |
for an explanation. |
331 |
|
332 |
Currently, the stats are always 64-bit-stats, i.e. instead of returning an |
333 |
error when stat'ing a large file, the results will be silently truncated |
334 |
unless perl itself is compiled with large file support. |
335 |
|
336 |
Example: Print the length of F</etc/passwd>: |
337 |
|
338 |
aio_stat "/etc/passwd", sub { |
339 |
$_[0] and die "stat failed: $!"; |
340 |
print "size is ", -s _, "\n"; |
341 |
}; |
342 |
|
343 |
=item aio_unlink $pathname, $callback->($status) |
344 |
|
345 |
Asynchronously unlink (delete) a file and call the callback with the |
346 |
result code. |
347 |
|
348 |
=item aio_link $srcpath, $dstpath, $callback->($status) |
349 |
|
350 |
Asynchronously create a new link to the existing object at C<$srcpath> at |
351 |
the path C<$dstpath> and call the callback with the result code. |
352 |
|
353 |
=item aio_symlink $srcpath, $dstpath, $callback->($status) |
354 |
|
355 |
Asynchronously create a new symbolic link to the existing object at C<$srcpath> at |
356 |
the path C<$dstpath> and call the callback with the result code. |
357 |
|
358 |
=item aio_rename $srcpath, $dstpath, $callback->($status) |
359 |
|
360 |
Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as |
361 |
rename(2) and call the callback with the result code. |
362 |
|
363 |
=item aio_rmdir $pathname, $callback->($status) |
364 |
|
365 |
Asynchronously rmdir (delete) a directory and call the callback with the |
366 |
result code. |
367 |
|
368 |
=item aio_readdir $pathname, $callback->($entries) |
369 |
|
370 |
Unlike the POSIX call of the same name, C<aio_readdir> reads an entire |
371 |
directory (i.e. opendir + readdir + closedir). The entries will not be |
372 |
sorted, and will B<NOT> include the C<.> and C<..> entries. |
373 |
|
374 |
The callback a single argument which is either C<undef> or an array-ref |
375 |
with the filenames. |
376 |
|
377 |
=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) |
378 |
|
379 |
Scans a directory (similar to C<aio_readdir>) but additionally tries to |
380 |
separate the entries of directory C<$path> into two sets of names, ones |
381 |
you can recurse into (directories or links to them), and ones you cannot |
382 |
recurse into (everything else). |
383 |
|
384 |
C<aio_scandir> is a composite request that creates of many sub requests_ |
385 |
C<$maxreq> specifies the maximum number of outstanding aio requests that |
386 |
this function generates. If it is C<< <= 0 >>, then a suitable default |
387 |
will be chosen (currently 6). |
388 |
|
389 |
On error, the callback is called without arguments, otherwise it receives |
390 |
two array-refs with path-relative entry names. |
391 |
|
392 |
Example: |
393 |
|
394 |
aio_scandir $dir, 0, sub { |
395 |
my ($dirs, $nondirs) = @_; |
396 |
print "real directories: @$dirs\n"; |
397 |
print "everything else: @$nondirs\n"; |
398 |
}; |
399 |
|
400 |
Implementation notes. |
401 |
|
402 |
The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can. |
403 |
|
404 |
After reading the directory, the modification time, size etc. of the |
405 |
directory before and after the readdir is checked, and if they match (and |
406 |
isn't the current time), the link count will be used to decide how many |
407 |
entries are directories (if >= 2). Otherwise, no knowledge of the number |
408 |
of subdirectories will be assumed. |
409 |
|
410 |
Then entries will be sorted into likely directories (everything without |
411 |
a non-initial dot currently) and likely non-directories (everything |
412 |
else). Then every entry plus an appended C</.> will be C<stat>'ed, |
413 |
likely directories first. If that succeeds, it assumes that the entry |
414 |
is a directory or a symlink to directory (which will be checked |
415 |
seperately). This is often faster than stat'ing the entry itself because |
416 |
filesystems might detect the type of the entry without reading the inode |
417 |
data (e.g. ext2fs filetype feature). |
418 |
|
419 |
If the known number of directories (link count - 2) has been reached, the |
420 |
rest of the entries is assumed to be non-directories. |
421 |
|
422 |
This only works with certainty on POSIX (= UNIX) filesystems, which |
423 |
fortunately are the vast majority of filesystems around. |
424 |
|
425 |
It will also likely work on non-POSIX filesystems with reduced efficiency |
426 |
as those tend to return 0 or 1 as link counts, which disables the |
427 |
directory counting heuristic. |
428 |
|
429 |
=cut |
430 |
|
431 |
sub aio_scandir($$$) { |
432 |
my ($path, $maxreq, $cb) = @_; |
433 |
|
434 |
my $grp = aio_group $cb; |
435 |
|
436 |
$maxreq = 6 if $maxreq <= 0; |
437 |
|
438 |
# stat once |
439 |
add $grp aio_stat $path, sub { |
440 |
return $grp->result () if $_[0]; |
441 |
my $now = time; |
442 |
my $hash1 = join ":", (stat _)[0,1,3,7,9]; |
443 |
|
444 |
# read the directory entries |
445 |
add $grp aio_readdir $path, sub { |
446 |
my $entries = shift |
447 |
or return $grp->result (); |
448 |
|
449 |
# stat the dir another time |
450 |
add $grp aio_stat $path, sub { |
451 |
my $hash2 = join ":", (stat _)[0,1,3,7,9]; |
452 |
|
453 |
my $ndirs; |
454 |
|
455 |
# take the slow route if anything looks fishy |
456 |
if ($hash1 ne $hash2 or (stat _)[9] == $now) { |
457 |
$ndirs = -1; |
458 |
} else { |
459 |
# if nlink == 2, we are finished |
460 |
# on non-posix-fs's, we rely on nlink < 2 |
461 |
$ndirs = (stat _)[3] - 2 |
462 |
or return $grp->result ([], $entries); |
463 |
} |
464 |
|
465 |
# sort into likely dirs and likely nondirs |
466 |
# dirs == files without ".", short entries first |
467 |
$entries = [map $_->[0], |
468 |
sort { $b->[1] cmp $a->[1] } |
469 |
map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length], |
470 |
@$entries]; |
471 |
|
472 |
my (@dirs, @nondirs); |
473 |
|
474 |
my ($statcb, $schedcb); |
475 |
my $nreq = 0; |
476 |
|
477 |
my $statgrp = add $grp aio_group; |
478 |
|
479 |
$schedcb = sub { |
480 |
if (@$entries) { |
481 |
if ($nreq < $maxreq) { |
482 |
my $ent = pop @$entries; |
483 |
$nreq++; |
484 |
add $statgrp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) }; |
485 |
} |
486 |
} elsif (!$nreq) { |
487 |
# finished |
488 |
$statgrp->cancel; |
489 |
undef $statcb; |
490 |
undef $schedcb; |
491 |
$grp->result (\@dirs, \@nondirs); |
492 |
} |
493 |
}; |
494 |
$statcb = sub { |
495 |
my ($status, $entry) = @_; |
496 |
|
497 |
if ($status < 0) { |
498 |
$nreq--; |
499 |
push @nondirs, $entry; |
500 |
&$schedcb; |
501 |
} else { |
502 |
# need to check for real directory |
503 |
add $grp aio_lstat "$path/$entry", sub { |
504 |
$nreq--; |
505 |
|
506 |
if (-d _) { |
507 |
push @dirs, $entry; |
508 |
|
509 |
if (!--$ndirs) { |
510 |
push @nondirs, @$entries; |
511 |
$entries = []; |
512 |
} |
513 |
} else { |
514 |
push @nondirs, $entry; |
515 |
} |
516 |
|
517 |
&$schedcb; |
518 |
} |
519 |
} |
520 |
}; |
521 |
|
522 |
&$schedcb while @$entries && $nreq < $maxreq; |
523 |
}; |
524 |
}; |
525 |
}; |
526 |
|
527 |
$grp |
528 |
} |
529 |
|
530 |
=item aio_fsync $fh, $callback->($status) |
531 |
|
532 |
Asynchronously call fsync on the given filehandle and call the callback |
533 |
with the fsync result code. |
534 |
|
535 |
=item aio_fdatasync $fh, $callback->($status) |
536 |
|
537 |
Asynchronously call fdatasync on the given filehandle and call the |
538 |
callback with the fdatasync result code. |
539 |
|
540 |
If this call isn't available because your OS lacks it or it couldn't be |
541 |
detected, it will be emulated by calling C<fsync> instead. |
542 |
|
543 |
=item aio_group $callback->(...) |
544 |
|
545 |
[EXPERIMENTAL] |
546 |
|
547 |
This is a very special aio request: Instead of doing something, it is a |
548 |
container for other aio requests, which is useful if you want to bundle |
549 |
many requests into a single, composite, request with a definite callback |
550 |
and the ability to cancel the whole request with its subrequests. |
551 |
|
552 |
Returns an object of class L<IO::AIO::GRP>. See its documentation below |
553 |
for more info. |
554 |
|
555 |
Example: |
556 |
|
557 |
my $grp = aio_group sub { |
558 |
print "all stats done\n"; |
559 |
}; |
560 |
|
561 |
add $grp |
562 |
(aio_stat ...), |
563 |
(aio_stat ...), |
564 |
...; |
565 |
|
566 |
=item aio_nop $callback->() |
567 |
|
568 |
This is a special request - it does nothing in itself and is only used for |
569 |
side effects, such as when you want to add a dummy request to a group so |
570 |
that finishing the requests in the group depends on executing the given |
571 |
code. |
572 |
|
573 |
While this request does nothing, it still goes through the execution |
574 |
phase and still requires a worker thread. Thus, the callback will not |
575 |
be executed immediately but only after other requests in the queue have |
576 |
entered their execution phase. This can be used to measure request |
577 |
latency. |
578 |
|
579 |
=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED* |
580 |
|
581 |
Mainly used for debugging and benchmarking, this aio request puts one of |
582 |
the request workers to sleep for the given time. |
583 |
|
584 |
While it is theoretically handy to have simple I/O scheduling requests |
585 |
like sleep and file handle readable/writable, the overhead this creates is |
586 |
immense (it blocks a thread for a long time) so do not use this function |
587 |
except to put your application under artificial I/O pressure. |
588 |
|
589 |
=back |
590 |
|
591 |
=head2 IO::AIO::REQ CLASS |
592 |
|
593 |
All non-aggregate C<aio_*> functions return an object of this class when |
594 |
called in non-void context. |
595 |
|
596 |
A request always moves through the following five states in its lifetime, |
597 |
in order: B<ready> (request has been created, but has not been executed |
598 |
yet), B<execute> (request is currently being executed), B<pending> |
599 |
(request has been executed but callback has not been called yet), |
600 |
B<result> (results are being processed synchronously, includes calling the |
601 |
callback) and B<done> (request has reached the end of its lifetime and |
602 |
holds no resources anymore). |
603 |
|
604 |
=over 4 |
605 |
|
606 |
=item cancel $req |
607 |
|
608 |
Cancels the request, if possible. Has the effect of skipping execution |
609 |
when entering the B<execute> state and skipping calling the callback when |
610 |
entering the the B<result> state, but will leave the request otherwise |
611 |
untouched. That means that requests that currently execute will not be |
612 |
stopped and resources held by the request will not be freed prematurely. |
613 |
|
614 |
=item cb $req $callback->(...) |
615 |
|
616 |
Replace (or simply set) the callback registered to the request. |
617 |
|
618 |
=back |
619 |
|
620 |
=head2 IO::AIO::GRP CLASS |
621 |
|
622 |
This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to |
623 |
objects of this class, too. |
624 |
|
625 |
A IO::AIO::GRP object is a special request that can contain multiple other |
626 |
aio requests. |
627 |
|
628 |
You create one by calling the C<aio_group> constructing function with a |
629 |
callback that will be called when all contained requests have entered the |
630 |
C<done> state: |
631 |
|
632 |
my $grp = aio_group sub { |
633 |
print "all requests are done\n"; |
634 |
}; |
635 |
|
636 |
You add requests by calling the C<add> method with one or more |
637 |
C<IO::AIO::REQ> objects: |
638 |
|
639 |
$grp->add (aio_unlink "..."); |
640 |
|
641 |
add $grp aio_stat "...", sub { |
642 |
$_[0] or return $grp->result ("error"); |
643 |
|
644 |
# add another request dynamically, if first succeeded |
645 |
add $grp aio_open "...", sub { |
646 |
$grp->result ("ok"); |
647 |
}; |
648 |
}; |
649 |
|
650 |
This makes it very easy to create composite requests (see the source of |
651 |
C<aio_move> for an application) that work and feel like simple requests. |
652 |
|
653 |
=over 4 |
654 |
|
655 |
=item * The IO::AIO::GRP objects will be cleaned up during calls to |
656 |
C<IO::AIO::poll_cb>, just like any other request. |
657 |
|
658 |
=item * They can be canceled like any other request. Canceling will cancel not |
659 |
only the request itself, but also all requests it contains. |
660 |
|
661 |
=item * They can also can also be added to other IO::AIO::GRP objects. |
662 |
|
663 |
=item * You must not add requests to a group from within the group callback (or |
664 |
any later time). |
665 |
|
666 |
=item * This does not harmonise well with C<max_outstanding>, so best do |
667 |
not combine C<aio_group> with it. Groups and feeders are recommended for |
668 |
this kind of concurrency-limiting. |
669 |
|
670 |
=back |
671 |
|
672 |
Their lifetime, simplified, looks like this: when they are empty, they |
673 |
will finish very quickly. If they contain only requests that are in the |
674 |
C<done> state, they will also finish. Otherwise they will continue to |
675 |
exist. |
676 |
|
677 |
That means after creating a group you have some time to add requests. And |
678 |
in the callbacks of those requests, you can add further requests to the |
679 |
group. And only when all those requests have finished will the the group |
680 |
itself finish. |
681 |
|
682 |
=over 4 |
683 |
|
684 |
=item add $grp ... |
685 |
|
686 |
=item $grp->add (...) |
687 |
|
688 |
Add one or more requests to the group. Any type of L<IO::AIO::REQ> can |
689 |
be added, including other groups, as long as you do not create circular |
690 |
dependencies. |
691 |
|
692 |
Returns all its arguments. |
693 |
|
694 |
=item $grp->result (...) |
695 |
|
696 |
Set the result value(s) that will be passed to the group callback when all |
697 |
subrequests have finished. By default, no argument will be passed. |
698 |
|
699 |
=item feed $grp $callback->($grp) |
700 |
|
701 |
[VERY EXPERIMENTAL] |
702 |
|
703 |
Sets a feeder/generator on this group: every group can have an attached |
704 |
generator that generates requests if idle. The idea behind this is that, |
705 |
although you could just queue as many requests as you want in a group, |
706 |
this might starve other requests for a potentially long time. For |
707 |
example, C<aio_scandir> might generate hundreds of thousands C<aio_stat> |
708 |
requests, delaying any later requests for a long time. |
709 |
|
710 |
To avoid this, and allow incremental generation of requests, you can |
711 |
instead a group and set a feeder on it that generates those requests. The |
712 |
feed callback will be called whenever there are few enough (see C<limit>, |
713 |
below) requests active in the group itself and is expected to queue more |
714 |
requests. |
715 |
|
716 |
The feed callback can queue as many requests as it likes (i.e. C<add> does |
717 |
not impose any limits). |
718 |
|
719 |
If the feed does not queue more requests when called, it will be |
720 |
automatically removed from the group. |
721 |
|
722 |
If the feed limit is C<0>, it will be set to C<2> automatically. |
723 |
|
724 |
Example: |
725 |
|
726 |
# stat all files in @files, but only ever use four aio requests concurrently: |
727 |
|
728 |
my $grp = aio_group sub { print "finished\n" }; |
729 |
limit $grp 4; |
730 |
feed $grp sub { |
731 |
my $file = pop @files |
732 |
or return; |
733 |
|
734 |
add $grp aio_stat $file, sub { ... }; |
735 |
}; |
736 |
|
737 |
=item limit $grp $num |
738 |
|
739 |
Sets the feeder limit for the group: The feeder will be called whenever |
740 |
the group contains less than this many requests. |
741 |
|
742 |
Setting the limit to C<0> will pause the feeding process. |
743 |
|
744 |
=back |
745 |
|
746 |
=head2 SUPPORT FUNCTIONS |
747 |
|
748 |
=over 4 |
749 |
|
750 |
=item $fileno = IO::AIO::poll_fileno |
751 |
|
752 |
Return the I<request result pipe file descriptor>. This filehandle must be |
753 |
polled for reading by some mechanism outside this module (e.g. Event or |
754 |
select, see below or the SYNOPSIS). If the pipe becomes readable you have |
755 |
to call C<poll_cb> to check the results. |
756 |
|
757 |
See C<poll_cb> for an example. |
758 |
|
759 |
=item IO::AIO::poll_cb |
760 |
|
761 |
Process all outstanding events on the result pipe. You have to call this |
762 |
regularly. Returns the number of events processed. Returns immediately |
763 |
when no events are outstanding. |
764 |
|
765 |
Example: Install an Event watcher that automatically calls |
766 |
IO::AIO::poll_cb with high priority: |
767 |
|
768 |
Event->io (fd => IO::AIO::poll_fileno, |
769 |
poll => 'r', async => 1, |
770 |
cb => \&IO::AIO::poll_cb); |
771 |
|
772 |
=item IO::AIO::poll_wait |
773 |
|
774 |
Wait till the result filehandle becomes ready for reading (simply does a |
775 |
C<select> on the filehandle. This is useful if you want to synchronously wait |
776 |
for some requests to finish). |
777 |
|
778 |
See C<nreqs> for an example. |
779 |
|
780 |
=item IO::AIO::nreqs |
781 |
|
782 |
Returns the number of requests currently outstanding (i.e. for which their |
783 |
callback has not been invoked yet). |
784 |
|
785 |
Example: wait till there are no outstanding requests anymore: |
786 |
|
787 |
IO::AIO::poll_wait, IO::AIO::poll_cb |
788 |
while IO::AIO::nreqs; |
789 |
|
790 |
=item IO::AIO::flush |
791 |
|
792 |
Wait till all outstanding AIO requests have been handled. |
793 |
|
794 |
Strictly equivalent to: |
795 |
|
796 |
IO::AIO::poll_wait, IO::AIO::poll_cb |
797 |
while IO::AIO::nreqs; |
798 |
|
799 |
=item IO::AIO::poll |
800 |
|
801 |
Waits until some requests have been handled. |
802 |
|
803 |
Strictly equivalent to: |
804 |
|
805 |
IO::AIO::poll_wait, IO::AIO::poll_cb |
806 |
if IO::AIO::nreqs; |
807 |
|
808 |
=item IO::AIO::min_parallel $nthreads |
809 |
|
810 |
Set the minimum number of AIO threads to C<$nthreads>. The current |
811 |
default is C<8>, which means eight asynchronous operations can execute |
812 |
concurrently at any one time (the number of outstanding requests, |
813 |
however, is unlimited). |
814 |
|
815 |
IO::AIO starts threads only on demand, when an AIO request is queued and |
816 |
no free thread exists. |
817 |
|
818 |
It is recommended to keep the number of threads relatively low, as some |
819 |
Linux kernel versions will scale negatively with the number of threads |
820 |
(higher parallelity => MUCH higher latency). With current Linux 2.6 |
821 |
versions, 4-32 threads should be fine. |
822 |
|
823 |
Under most circumstances you don't need to call this function, as the |
824 |
module selects a default that is suitable for low to moderate load. |
825 |
|
826 |
=item IO::AIO::max_parallel $nthreads |
827 |
|
828 |
Sets the maximum number of AIO threads to C<$nthreads>. If more than the |
829 |
specified number of threads are currently running, this function kills |
830 |
them. This function blocks until the limit is reached. |
831 |
|
832 |
While C<$nthreads> are zero, aio requests get queued but not executed |
833 |
until the number of threads has been increased again. |
834 |
|
835 |
This module automatically runs C<max_parallel 0> at program end, to ensure |
836 |
that all threads are killed and that there are no outstanding requests. |
837 |
|
838 |
Under normal circumstances you don't need to call this function. |
839 |
|
840 |
=item $oldnreqs = IO::AIO::max_outstanding $nreqs |
841 |
|
842 |
[DEPRECATED] |
843 |
|
844 |
Sets the maximum number of outstanding requests to C<$nreqs>. If you |
845 |
try to queue up more than this number of requests, the caller will block until |
846 |
some requests have been handled. |
847 |
|
848 |
The default is very large, so normally there is no practical limit. If you |
849 |
queue up many requests in a loop it often improves speed if you set |
850 |
this to a relatively low number, such as C<100>. |
851 |
|
852 |
This function does not work well together with C<aio_group>'s, and their |
853 |
feeder interface is better suited to limiting concurrency, so do not use |
854 |
this function. |
855 |
|
856 |
Under normal circumstances you don't need to call this function. |
857 |
|
858 |
=back |
859 |
|
860 |
=cut |
861 |
|
862 |
# support function to convert a fd into a perl filehandle |
863 |
sub _fd2fh { |
864 |
return undef if $_[0] < 0; |
865 |
|
866 |
# try to generate nice filehandles |
867 |
my $sym = "IO::AIO::fd#$_[0]"; |
868 |
local *$sym; |
869 |
|
870 |
open *$sym, "+<&=$_[0]" # usually works under any unix |
871 |
or open *$sym, "<&=$_[0]" # cygwin needs this |
872 |
or open *$sym, ">&=$_[0]" # or this |
873 |
or return undef; |
874 |
|
875 |
*$sym |
876 |
} |
877 |
|
878 |
min_parallel 8; |
879 |
|
880 |
END { |
881 |
max_parallel 0; |
882 |
} |
883 |
|
884 |
1; |
885 |
|
886 |
=head2 FORK BEHAVIOUR |
887 |
|
888 |
This module should do "the right thing" when the process using it forks: |
889 |
|
890 |
Before the fork, IO::AIO enters a quiescent state where no requests |
891 |
can be added in other threads and no results will be processed. After |
892 |
the fork the parent simply leaves the quiescent state and continues |
893 |
request/result processing, while the child clears the request/result |
894 |
queue (so the requests started before the fork will only be handled in |
895 |
the parent). Threads will be started on demand until the limit ste in the |
896 |
parent process has been reached again. |
897 |
|
898 |
In short: the parent will, after a short pause, continue as if fork had |
899 |
not been called, while the child will act as if IO::AIO has not been used |
900 |
yet. |
901 |
|
902 |
=head2 MEMORY USAGE |
903 |
|
904 |
Each aio request uses - depending on your architecture - around 128 bytes |
905 |
of memory. In addition, stat requests need a stat buffer (possibly a few |
906 |
hundred bytes). Perl scalars and other data passed into aio requests will |
907 |
also be locked. |
908 |
|
909 |
This is now awfully much, so queuing lots of requests is not usually a |
910 |
problem. |
911 |
|
912 |
Each thread needs a stack area which is usually around 16k, sometimes much |
913 |
larger, depending on the OS. |
914 |
|
915 |
=head1 SEE ALSO |
916 |
|
917 |
L<Coro::AIO>. |
918 |
|
919 |
=head1 AUTHOR |
920 |
|
921 |
Marc Lehmann <schmorp@schmorp.de> |
922 |
http://home.schmorp.de/ |
923 |
|
924 |
=cut |
925 |
|