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 |
use IO::AIO 2; # version has aio objects |
21 |
|
22 |
my $req = aio_unlink "/tmp/file", sub { }; |
23 |
$req->cancel; # cancel request if still in queue |
24 |
|
25 |
# AnyEvent |
26 |
open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!"; |
27 |
my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb }); |
28 |
|
29 |
# Event |
30 |
Event->io (fd => IO::AIO::poll_fileno, |
31 |
poll => 'r', |
32 |
cb => \&IO::AIO::poll_cb); |
33 |
|
34 |
# Glib/Gtk2 |
35 |
add_watch Glib::IO IO::AIO::poll_fileno, |
36 |
in => sub { IO::AIO::poll_cb; 1 }; |
37 |
|
38 |
# Tk |
39 |
Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "", |
40 |
readable => \&IO::AIO::poll_cb); |
41 |
|
42 |
# Danga::Socket |
43 |
Danga::Socket->AddOtherFds (IO::AIO::poll_fileno => |
44 |
\&IO::AIO::poll_cb); |
45 |
|
46 |
|
47 |
=head1 DESCRIPTION |
48 |
|
49 |
This module implements asynchronous I/O using whatever means your |
50 |
operating system supports. |
51 |
|
52 |
Currently, a number of threads are started that execute your read/writes |
53 |
and signal their completion. You don't need thread support in your libc or |
54 |
perl, and the threads created by this module will not be visible to the |
55 |
pthreads library. In the future, this module might make use of the native |
56 |
aio functions available on many operating systems. However, they are often |
57 |
not well-supported (Linux doesn't allow them on normal files currently, |
58 |
for example), and they would only support aio_read and aio_write, so the |
59 |
remaining functionality would have to be implemented using threads anyway. |
60 |
|
61 |
Although the module will work with in the presence of other threads, it is |
62 |
currently not reentrant, so use appropriate locking yourself, always call |
63 |
C<poll_cb> from within the same thread, or never call C<poll_cb> (or other |
64 |
C<aio_> functions) recursively. |
65 |
|
66 |
=cut |
67 |
|
68 |
package IO::AIO; |
69 |
|
70 |
no warnings; |
71 |
use strict 'vars'; |
72 |
|
73 |
use base 'Exporter'; |
74 |
|
75 |
BEGIN { |
76 |
our $VERSION = '1.99'; |
77 |
|
78 |
our @EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat |
79 |
aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink |
80 |
aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move); |
81 |
our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs); |
82 |
|
83 |
require XSLoader; |
84 |
XSLoader::load ("IO::AIO", $VERSION); |
85 |
} |
86 |
|
87 |
=head1 FUNCTIONS |
88 |
|
89 |
=head2 AIO FUNCTIONS |
90 |
|
91 |
All the C<aio_*> calls are more or less thin wrappers around the syscall |
92 |
with the same name (sans C<aio_>). The arguments are similar or identical, |
93 |
and they all accept an additional (and optional) C<$callback> argument |
94 |
which must be a code reference. This code reference will get called with |
95 |
the syscall return code (e.g. most syscalls return C<-1> on error, unlike |
96 |
perl, which usually delivers "false") as it's sole argument when the given |
97 |
syscall has been executed asynchronously. |
98 |
|
99 |
All functions expecting a filehandle keep a copy of the filehandle |
100 |
internally until the request has finished. |
101 |
|
102 |
All non-composite requests (requests that are not broken down into |
103 |
multiple requests) return objects of type L<IO::AIO::REQ> that allow |
104 |
further manipulation of running requests. |
105 |
|
106 |
The pathnames you pass to these routines I<must> be absolute and |
107 |
encoded in byte form. The reason for the former is that at the time the |
108 |
request is being executed, the current working directory could have |
109 |
changed. Alternatively, you can make sure that you never change the |
110 |
current working directory. |
111 |
|
112 |
To encode pathnames to byte form, either make sure you either: a) |
113 |
always pass in filenames you got from outside (command line, readdir |
114 |
etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode |
115 |
your pathnames to the locale (or other) encoding in effect in the user |
116 |
environment, d) use Glib::filename_from_unicode on unicode filenames or e) |
117 |
use something else. |
118 |
|
119 |
=over 4 |
120 |
|
121 |
=item aio_open $pathname, $flags, $mode, $callback->($fh) |
122 |
|
123 |
Asynchronously open or create a file and call the callback with a newly |
124 |
created filehandle for the file. |
125 |
|
126 |
The pathname passed to C<aio_open> must be absolute. See API NOTES, above, |
127 |
for an explanation. |
128 |
|
129 |
The C<$flags> argument is a bitmask. See the C<Fcntl> module for a |
130 |
list. They are the same as used by C<sysopen>. |
131 |
|
132 |
Likewise, C<$mode> specifies the mode of the newly created file, if it |
133 |
didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>, |
134 |
except that it is mandatory (i.e. use C<0> if you don't create new files, |
135 |
and C<0666> or C<0777> if you do). |
136 |
|
137 |
Example: |
138 |
|
139 |
aio_open "/etc/passwd", O_RDONLY, 0, sub { |
140 |
if ($_[0]) { |
141 |
print "open successful, fh is $_[0]\n"; |
142 |
... |
143 |
} else { |
144 |
die "open failed: $!\n"; |
145 |
} |
146 |
}; |
147 |
|
148 |
=item aio_close $fh, $callback->($status) |
149 |
|
150 |
Asynchronously close a file and call the callback with the result |
151 |
code. I<WARNING:> although accepted, you should not pass in a perl |
152 |
filehandle here, as perl will likely close the file descriptor another |
153 |
time when the filehandle is destroyed. Normally, you can safely call perls |
154 |
C<close> or just let filehandles go out of scope. |
155 |
|
156 |
This is supposed to be a bug in the API, so that might change. It's |
157 |
therefore best to avoid this function. |
158 |
|
159 |
=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) |
160 |
|
161 |
=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) |
162 |
|
163 |
Reads or writes C<length> bytes from the specified C<fh> and C<offset> |
164 |
into the scalar given by C<data> and offset C<dataoffset> and calls the |
165 |
callback without the actual number of bytes read (or -1 on error, just |
166 |
like the syscall). |
167 |
|
168 |
The C<$data> scalar I<MUST NOT> be modified in any way while the request |
169 |
is outstanding. Modifying it can result in segfaults or WW3 (if the |
170 |
necessary/optional hardware is installed). |
171 |
|
172 |
Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at |
173 |
offset C<0> within the scalar: |
174 |
|
175 |
aio_read $fh, 7, 15, $buffer, 0, sub { |
176 |
$_[0] > 0 or die "read error: $!"; |
177 |
print "read $_[0] bytes: <$buffer>\n"; |
178 |
}; |
179 |
|
180 |
=item aio_move $srcpath, $dstpath, $callback->($status) |
181 |
|
182 |
Try to move the I<file> (directories not supported as either source or |
183 |
destination) from C<$srcpath> to C<$dstpath> and call the callback with |
184 |
the C<0> (error) or C<-1> ok. |
185 |
|
186 |
This is a composite request that tries to rename(2) the file first. If |
187 |
rename files with C<EXDEV>, it creates the destination file with mode 0200 |
188 |
and copies the contents of the source file into it using C<aio_sendfile>, |
189 |
followed by restoring atime, mtime, access mode and uid/gid, in that |
190 |
order, and unlinking the C<$srcpath>. |
191 |
|
192 |
If an error occurs, the partial destination file will be unlinked, if |
193 |
possible, except when setting atime, mtime, access mode and uid/gid, where |
194 |
errors are being ignored. |
195 |
|
196 |
=cut |
197 |
|
198 |
sub aio_move($$$) { |
199 |
my ($src, $dst, $cb) = @_; |
200 |
|
201 |
aio_rename $src, $dst, sub { |
202 |
if ($_[0] && $! == EXDEV) { |
203 |
aio_open $src, O_RDONLY, 0, sub { |
204 |
if (my $src_fh = $_[0]) { |
205 |
my @stat = stat $src_fh; |
206 |
|
207 |
aio_open $dst, O_WRONLY, 0200, sub { |
208 |
if (my $dst_fh = $_[0]) { |
209 |
aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub { |
210 |
close $src_fh; |
211 |
|
212 |
if ($_[0] == $stat[7]) { |
213 |
utime $stat[8], $stat[9], $dst; |
214 |
chmod $stat[2] & 07777, $dst_fh; |
215 |
chown $stat[4], $stat[5], $dst_fh; |
216 |
close $dst_fh; |
217 |
|
218 |
aio_unlink $src, sub { |
219 |
$cb->($_[0]); |
220 |
}; |
221 |
} else { |
222 |
my $errno = $!; |
223 |
aio_unlink $dst, sub { |
224 |
$! = $errno; |
225 |
$cb->(-1); |
226 |
}; |
227 |
} |
228 |
}; |
229 |
} else { |
230 |
$cb->(-1); |
231 |
} |
232 |
}, |
233 |
|
234 |
} else { |
235 |
$cb->(-1); |
236 |
} |
237 |
}; |
238 |
} else { |
239 |
$cb->($_[0]); |
240 |
} |
241 |
}; |
242 |
} |
243 |
|
244 |
=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) |
245 |
|
246 |
Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts |
247 |
reading at byte offset C<$in_offset>, and starts writing at the current |
248 |
file offset of C<$out_fh>. Because of that, it is not safe to issue more |
249 |
than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each |
250 |
other. |
251 |
|
252 |
This call tries to make use of a native C<sendfile> syscall to provide |
253 |
zero-copy operation. For this to work, C<$out_fh> should refer to a |
254 |
socket, and C<$in_fh> should refer to mmap'able file. |
255 |
|
256 |
If the native sendfile call fails or is not implemented, it will be |
257 |
emulated, so you can call C<aio_sendfile> on any type of filehandle |
258 |
regardless of the limitations of the operating system. |
259 |
|
260 |
Please note, however, that C<aio_sendfile> can read more bytes from |
261 |
C<$in_fh> than are written, and there is no way to find out how many |
262 |
bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only |
263 |
provides the number of bytes written to C<$out_fh>. Only if the result |
264 |
value equals C<$length> one can assume that C<$length> bytes have been |
265 |
read. |
266 |
|
267 |
=item aio_readahead $fh,$offset,$length, $callback->($retval) |
268 |
|
269 |
C<aio_readahead> populates the page cache with data from a file so that |
270 |
subsequent reads from that file will not block on disk I/O. The C<$offset> |
271 |
argument specifies the starting point from which data is to be read and |
272 |
C<$length> specifies the number of bytes to be read. I/O is performed in |
273 |
whole pages, so that offset is effectively rounded down to a page boundary |
274 |
and bytes are read up to the next page boundary greater than or equal to |
275 |
(off-set+length). C<aio_readahead> does not read beyond the end of the |
276 |
file. The current file offset of the file is left unchanged. |
277 |
|
278 |
If that syscall doesn't exist (likely if your OS isn't Linux) it will be |
279 |
emulated by simply reading the data, which would have a similar effect. |
280 |
|
281 |
=item aio_stat $fh_or_path, $callback->($status) |
282 |
|
283 |
=item aio_lstat $fh, $callback->($status) |
284 |
|
285 |
Works like perl's C<stat> or C<lstat> in void context. The callback will |
286 |
be called after the stat and the results will be available using C<stat _> |
287 |
or C<-s _> etc... |
288 |
|
289 |
The pathname passed to C<aio_stat> must be absolute. See API NOTES, above, |
290 |
for an explanation. |
291 |
|
292 |
Currently, the stats are always 64-bit-stats, i.e. instead of returning an |
293 |
error when stat'ing a large file, the results will be silently truncated |
294 |
unless perl itself is compiled with large file support. |
295 |
|
296 |
Example: Print the length of F</etc/passwd>: |
297 |
|
298 |
aio_stat "/etc/passwd", sub { |
299 |
$_[0] and die "stat failed: $!"; |
300 |
print "size is ", -s _, "\n"; |
301 |
}; |
302 |
|
303 |
=item aio_unlink $pathname, $callback->($status) |
304 |
|
305 |
Asynchronously unlink (delete) a file and call the callback with the |
306 |
result code. |
307 |
|
308 |
=item aio_link $srcpath, $dstpath, $callback->($status) |
309 |
|
310 |
Asynchronously create a new link to the existing object at C<$srcpath> at |
311 |
the path C<$dstpath> and call the callback with the result code. |
312 |
|
313 |
=item aio_symlink $srcpath, $dstpath, $callback->($status) |
314 |
|
315 |
Asynchronously create a new symbolic link to the existing object at C<$srcpath> at |
316 |
the path C<$dstpath> and call the callback with the result code. |
317 |
|
318 |
=item aio_rename $srcpath, $dstpath, $callback->($status) |
319 |
|
320 |
Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as |
321 |
rename(2) and call the callback with the result code. |
322 |
|
323 |
=item aio_rmdir $pathname, $callback->($status) |
324 |
|
325 |
Asynchronously rmdir (delete) a directory and call the callback with the |
326 |
result code. |
327 |
|
328 |
=item aio_readdir $pathname, $callback->($entries) |
329 |
|
330 |
Unlike the POSIX call of the same name, C<aio_readdir> reads an entire |
331 |
directory (i.e. opendir + readdir + closedir). The entries will not be |
332 |
sorted, and will B<NOT> include the C<.> and C<..> entries. |
333 |
|
334 |
The callback a single argument which is either C<undef> or an array-ref |
335 |
with the filenames. |
336 |
|
337 |
=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) |
338 |
|
339 |
Scans a directory (similar to C<aio_readdir>) but additionally tries to |
340 |
separate the entries of directory C<$path> into two sets of names, ones |
341 |
you can recurse into (directories or links to them), and ones you cannot |
342 |
recurse into (everything else). |
343 |
|
344 |
C<aio_scandir> is a composite request that consists of many sub |
345 |
requests. C<$maxreq> specifies the maximum number of outstanding aio |
346 |
requests that this function generates. If it is C<< <= 0 >>, then a |
347 |
suitable default will be chosen (currently 8). |
348 |
|
349 |
On error, the callback is called without arguments, otherwise it receives |
350 |
two array-refs with path-relative entry names. |
351 |
|
352 |
Example: |
353 |
|
354 |
aio_scandir $dir, 0, sub { |
355 |
my ($dirs, $nondirs) = @_; |
356 |
print "real directories: @$dirs\n"; |
357 |
print "everything else: @$nondirs\n"; |
358 |
}; |
359 |
|
360 |
Implementation notes. |
361 |
|
362 |
The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can. |
363 |
|
364 |
After reading the directory, the modification time, size etc. of the |
365 |
directory before and after the readdir is checked, and if they match (and |
366 |
isn't the current time), the link count will be used to decide how many |
367 |
entries are directories (if >= 2). Otherwise, no knowledge of the number |
368 |
of subdirectories will be assumed. |
369 |
|
370 |
Then entries will be sorted into likely directories (everything without |
371 |
a non-initial dot currently) and likely non-directories (everything |
372 |
else). Then every entry plus an appended C</.> will be C<stat>'ed, |
373 |
likely directories first. If that succeeds, it assumes that the entry |
374 |
is a directory or a symlink to directory (which will be checked |
375 |
seperately). This is often faster than stat'ing the entry itself because |
376 |
filesystems might detect the type of the entry without reading the inode |
377 |
data (e.g. ext2fs filetype feature). |
378 |
|
379 |
If the known number of directories (link count - 2) has been reached, the |
380 |
rest of the entries is assumed to be non-directories. |
381 |
|
382 |
This only works with certainty on POSIX (= UNIX) filesystems, which |
383 |
fortunately are the vast majority of filesystems around. |
384 |
|
385 |
It will also likely work on non-POSIX filesystems with reduced efficiency |
386 |
as those tend to return 0 or 1 as link counts, which disables the |
387 |
directory counting heuristic. |
388 |
|
389 |
=cut |
390 |
|
391 |
sub aio_scandir($$$) { |
392 |
my ($path, $maxreq, $cb) = @_; |
393 |
|
394 |
$maxreq = 8 if $maxreq <= 0; |
395 |
|
396 |
# stat once |
397 |
aio_stat $path, sub { |
398 |
return $cb->() if $_[0]; |
399 |
my $now = time; |
400 |
my $hash1 = join ":", (stat _)[0,1,3,7,9]; |
401 |
|
402 |
# read the directory entries |
403 |
aio_readdir $path, sub { |
404 |
my $entries = shift |
405 |
or return $cb->(); |
406 |
|
407 |
# stat the dir another time |
408 |
aio_stat $path, sub { |
409 |
my $hash2 = join ":", (stat _)[0,1,3,7,9]; |
410 |
|
411 |
my $ndirs; |
412 |
|
413 |
# take the slow route if anything looks fishy |
414 |
if ($hash1 ne $hash2 or (stat _)[9] == $now) { |
415 |
$ndirs = -1; |
416 |
} else { |
417 |
# if nlink == 2, we are finished |
418 |
# on non-posix-fs's, we rely on nlink < 2 |
419 |
$ndirs = (stat _)[3] - 2 |
420 |
or return $cb->([], $entries); |
421 |
} |
422 |
|
423 |
# sort into likely dirs and likely nondirs |
424 |
# dirs == files without ".", short entries first |
425 |
$entries = [map $_->[0], |
426 |
sort { $b->[1] cmp $a->[1] } |
427 |
map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length], |
428 |
@$entries]; |
429 |
|
430 |
my (@dirs, @nondirs); |
431 |
|
432 |
my ($statcb, $schedcb); |
433 |
my $nreq = 0; |
434 |
|
435 |
$schedcb = sub { |
436 |
if (@$entries) { |
437 |
if ($nreq < $maxreq) { |
438 |
my $ent = pop @$entries; |
439 |
$nreq++; |
440 |
aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) }; |
441 |
} |
442 |
} elsif (!$nreq) { |
443 |
# finished |
444 |
undef $statcb; |
445 |
undef $schedcb; |
446 |
$cb->(\@dirs, \@nondirs) if $cb; |
447 |
undef $cb; |
448 |
} |
449 |
}; |
450 |
$statcb = sub { |
451 |
my ($status, $entry) = @_; |
452 |
|
453 |
if ($status < 0) { |
454 |
$nreq--; |
455 |
push @nondirs, $entry; |
456 |
&$schedcb; |
457 |
} else { |
458 |
# need to check for real directory |
459 |
aio_lstat "$path/$entry", sub { |
460 |
$nreq--; |
461 |
|
462 |
if (-d _) { |
463 |
push @dirs, $entry; |
464 |
|
465 |
if (!--$ndirs) { |
466 |
push @nondirs, @$entries; |
467 |
$entries = []; |
468 |
} |
469 |
} else { |
470 |
push @nondirs, $entry; |
471 |
} |
472 |
|
473 |
&$schedcb; |
474 |
} |
475 |
} |
476 |
}; |
477 |
|
478 |
&$schedcb while @$entries && $nreq < $maxreq; |
479 |
}; |
480 |
}; |
481 |
}; |
482 |
} |
483 |
|
484 |
=item aio_fsync $fh, $callback->($status) |
485 |
|
486 |
Asynchronously call fsync on the given filehandle and call the callback |
487 |
with the fsync result code. |
488 |
|
489 |
=item aio_fdatasync $fh, $callback->($status) |
490 |
|
491 |
Asynchronously call fdatasync on the given filehandle and call the |
492 |
callback with the fdatasync result code. |
493 |
|
494 |
If this call isn't available because your OS lacks it or it couldn't be |
495 |
detected, it will be emulated by calling C<fsync> instead. |
496 |
|
497 |
=back |
498 |
|
499 |
=head2 IO::AIO::REQ CLASS |
500 |
|
501 |
All non-aggregate C<aio_*> functions return an object of this class when |
502 |
called in non-void context. |
503 |
|
504 |
A request always moves through the following five states in its lifetime, |
505 |
in order: B<ready> (request has been created, but has not been executed |
506 |
yet), B<execute> (request is currently being executed), B<pending> |
507 |
(request has been executed but callback has not been called yet), |
508 |
B<result> (results are being processed synchronously, includes calling the |
509 |
callback) and B<done> (request has reached the end of its lifetime and |
510 |
holds no resources anymore). |
511 |
|
512 |
=over 4 |
513 |
|
514 |
=item $req->cancel |
515 |
|
516 |
Cancels the request, if possible. Has the effect of skipping execution |
517 |
when entering the B<execute> state and skipping calling the callback when |
518 |
entering the the B<result> state, but will leave the request otherwise |
519 |
untouched. That means that requests that currently execute will not be |
520 |
stopped and resources held by the request will not be freed prematurely. |
521 |
|
522 |
=back |
523 |
|
524 |
=head2 SUPPORT FUNCTIONS |
525 |
|
526 |
=over 4 |
527 |
|
528 |
=item $fileno = IO::AIO::poll_fileno |
529 |
|
530 |
Return the I<request result pipe file descriptor>. This filehandle must be |
531 |
polled for reading by some mechanism outside this module (e.g. Event or |
532 |
select, see below or the SYNOPSIS). If the pipe becomes readable you have |
533 |
to call C<poll_cb> to check the results. |
534 |
|
535 |
See C<poll_cb> for an example. |
536 |
|
537 |
=item IO::AIO::poll_cb |
538 |
|
539 |
Process all outstanding events on the result pipe. You have to call this |
540 |
regularly. Returns the number of events processed. Returns immediately |
541 |
when no events are outstanding. |
542 |
|
543 |
Example: Install an Event watcher that automatically calls |
544 |
IO::AIO::poll_cb with high priority: |
545 |
|
546 |
Event->io (fd => IO::AIO::poll_fileno, |
547 |
poll => 'r', async => 1, |
548 |
cb => \&IO::AIO::poll_cb); |
549 |
|
550 |
=item IO::AIO::poll_wait |
551 |
|
552 |
Wait till the result filehandle becomes ready for reading (simply does a |
553 |
C<select> on the filehandle. This is useful if you want to synchronously wait |
554 |
for some requests to finish). |
555 |
|
556 |
See C<nreqs> for an example. |
557 |
|
558 |
=item IO::AIO::nreqs |
559 |
|
560 |
Returns the number of requests currently outstanding (i.e. for which their |
561 |
callback has not been invoked yet). |
562 |
|
563 |
Example: wait till there are no outstanding requests anymore: |
564 |
|
565 |
IO::AIO::poll_wait, IO::AIO::poll_cb |
566 |
while IO::AIO::nreqs; |
567 |
|
568 |
=item IO::AIO::flush |
569 |
|
570 |
Wait till all outstanding AIO requests have been handled. |
571 |
|
572 |
Strictly equivalent to: |
573 |
|
574 |
IO::AIO::poll_wait, IO::AIO::poll_cb |
575 |
while IO::AIO::nreqs; |
576 |
|
577 |
=item IO::AIO::poll |
578 |
|
579 |
Waits until some requests have been handled. |
580 |
|
581 |
Strictly equivalent to: |
582 |
|
583 |
IO::AIO::poll_wait, IO::AIO::poll_cb |
584 |
if IO::AIO::nreqs; |
585 |
|
586 |
=item IO::AIO::min_parallel $nthreads |
587 |
|
588 |
Set the minimum number of AIO threads to C<$nthreads>. The current default |
589 |
is C<4>, which means four asynchronous operations can be done at one time |
590 |
(the number of outstanding operations, however, is unlimited). |
591 |
|
592 |
IO::AIO starts threads only on demand, when an AIO request is queued and |
593 |
no free thread exists. |
594 |
|
595 |
It is recommended to keep the number of threads low, as some Linux |
596 |
kernel versions will scale negatively with the number of threads (higher |
597 |
parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32 |
598 |
threads should be fine. |
599 |
|
600 |
Under most circumstances you don't need to call this function, as the |
601 |
module selects a default that is suitable for low to moderate load. |
602 |
|
603 |
=item IO::AIO::max_parallel $nthreads |
604 |
|
605 |
Sets the maximum number of AIO threads to C<$nthreads>. If more than the |
606 |
specified number of threads are currently running, this function kills |
607 |
them. This function blocks until the limit is reached. |
608 |
|
609 |
While C<$nthreads> are zero, aio requests get queued but not executed |
610 |
until the number of threads has been increased again. |
611 |
|
612 |
This module automatically runs C<max_parallel 0> at program end, to ensure |
613 |
that all threads are killed and that there are no outstanding requests. |
614 |
|
615 |
Under normal circumstances you don't need to call this function. |
616 |
|
617 |
=item $oldnreqs = IO::AIO::max_outstanding $nreqs |
618 |
|
619 |
Sets the maximum number of outstanding requests to C<$nreqs>. If you |
620 |
try to queue up more than this number of requests, the caller will block until |
621 |
some requests have been handled. |
622 |
|
623 |
The default is very large, so normally there is no practical limit. If you |
624 |
queue up many requests in a loop it often improves speed if you set |
625 |
this to a relatively low number, such as C<100>. |
626 |
|
627 |
Under normal circumstances you don't need to call this function. |
628 |
|
629 |
=back |
630 |
|
631 |
=cut |
632 |
|
633 |
# support function to convert a fd into a perl filehandle |
634 |
sub _fd2fh { |
635 |
return undef if $_[0] < 0; |
636 |
|
637 |
# try to generate nice filehandles |
638 |
my $sym = "IO::AIO::fd#$_[0]"; |
639 |
local *$sym; |
640 |
|
641 |
open *$sym, "+<&=$_[0]" # usually works under any unix |
642 |
or open *$sym, "<&=$_[0]" # cygwin needs this |
643 |
or open *$sym, ">&=$_[0]" # or this |
644 |
or return undef; |
645 |
|
646 |
*$sym |
647 |
} |
648 |
|
649 |
min_parallel 4; |
650 |
|
651 |
END { |
652 |
max_parallel 0; |
653 |
} |
654 |
|
655 |
1; |
656 |
|
657 |
=head2 FORK BEHAVIOUR |
658 |
|
659 |
This module should do "the right thing" when the process using it forks: |
660 |
|
661 |
Before the fork, IO::AIO enters a quiescent state where no requests |
662 |
can be added in other threads and no results will be processed. After |
663 |
the fork the parent simply leaves the quiescent state and continues |
664 |
request/result processing, while the child clears the request/result |
665 |
queue (so the requests started before the fork will only be handled in |
666 |
the parent). Threads will be started on demand until the limit ste in the |
667 |
parent process has been reached again. |
668 |
|
669 |
In short: the parent will, after a short pause, continue as if fork had |
670 |
not been called, while the child will act as if IO::AIO has not been used |
671 |
yet. |
672 |
|
673 |
=head1 SEE ALSO |
674 |
|
675 |
L<Coro>, L<Linux::AIO> (obsolete). |
676 |
|
677 |
=head1 AUTHOR |
678 |
|
679 |
Marc Lehmann <schmorp@schmorp.de> |
680 |
http://home.schmorp.de/ |
681 |
|
682 |
=cut |
683 |
|