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 = shift |
11 |
or die "/etc/passwd: $!"; |
12 |
... |
13 |
}; |
14 |
|
15 |
aio_unlink "/tmp/file", sub { }; |
16 |
|
17 |
aio_read $fh, 30000, 1024, $buffer, 0, sub { |
18 |
$_[0] > 0 or die "read error: $!"; |
19 |
}; |
20 |
|
21 |
# version 2+ has request and group objects |
22 |
use IO::AIO 2; |
23 |
|
24 |
aioreq_pri 4; # give next request a very high priority |
25 |
my $req = aio_unlink "/tmp/file", sub { }; |
26 |
$req->cancel; # cancel request if still in queue |
27 |
|
28 |
my $grp = aio_group sub { print "all stats done\n" }; |
29 |
add $grp aio_stat "..." for ...; |
30 |
|
31 |
# AnyEvent integration |
32 |
open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!"; |
33 |
my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb }); |
34 |
|
35 |
# Event integration |
36 |
Event->io (fd => IO::AIO::poll_fileno, |
37 |
poll => 'r', |
38 |
cb => \&IO::AIO::poll_cb); |
39 |
|
40 |
# Glib/Gtk2 integration |
41 |
add_watch Glib::IO IO::AIO::poll_fileno, |
42 |
in => sub { IO::AIO::poll_cb; 1 }; |
43 |
|
44 |
# Tk integration |
45 |
Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "", |
46 |
readable => \&IO::AIO::poll_cb); |
47 |
|
48 |
# Danga::Socket integration |
49 |
Danga::Socket->AddOtherFds (IO::AIO::poll_fileno => |
50 |
\&IO::AIO::poll_cb); |
51 |
|
52 |
=head1 DESCRIPTION |
53 |
|
54 |
This module implements asynchronous I/O using whatever means your |
55 |
operating system supports. |
56 |
|
57 |
Asynchronous means that operations that can normally block your program |
58 |
(e.g. reading from disk) will be done asynchronously: the operation |
59 |
will still block, but you can do something else in the meantime. This |
60 |
is extremely useful for programs that need to stay interactive even |
61 |
when doing heavy I/O (GUI programs, high performance network servers |
62 |
etc.), but can also be used to easily do operations in parallel that are |
63 |
normally done sequentially, e.g. stat'ing many files, which is much faster |
64 |
on a RAID volume or over NFS when you do a number of stat operations |
65 |
concurrently. |
66 |
|
67 |
While most of this works on all types of file descriptors (for |
68 |
example sockets), using these functions on file descriptors that |
69 |
support nonblocking operation (again, sockets, pipes etc.) is very |
70 |
inefficient. Use an event loop for that (such as the L<Event|Event> |
71 |
module): IO::AIO will naturally fit into such an event loop itself. |
72 |
|
73 |
In this version, a number of threads are started that execute your |
74 |
requests and signal their completion. You don't need thread support |
75 |
in perl, and the threads created by this module will not be visible |
76 |
to perl. In the future, this module might make use of the native aio |
77 |
functions available on many operating systems. However, they are often |
78 |
not well-supported or restricted (GNU/Linux doesn't allow them on normal |
79 |
files currently, for example), and they would only support aio_read and |
80 |
aio_write, so the remaining functionality would have to be implemented |
81 |
using threads anyway. |
82 |
|
83 |
Although the module will work in the presence of other (Perl-) threads, |
84 |
it is currently not reentrant in any way, so use appropriate locking |
85 |
yourself, always call C<poll_cb> from within the same thread, or never |
86 |
call C<poll_cb> (or other C<aio_> functions) recursively. |
87 |
|
88 |
=head2 EXAMPLE |
89 |
|
90 |
This is a simple example that uses the Event module and loads |
91 |
F</etc/passwd> asynchronously: |
92 |
|
93 |
use Fcntl; |
94 |
use Event; |
95 |
use IO::AIO; |
96 |
|
97 |
# register the IO::AIO callback with Event |
98 |
Event->io (fd => IO::AIO::poll_fileno, |
99 |
poll => 'r', |
100 |
cb => \&IO::AIO::poll_cb); |
101 |
|
102 |
# queue the request to open /etc/passwd |
103 |
aio_open "/etc/passwd", O_RDONLY, 0, sub { |
104 |
my $fh = shift |
105 |
or die "error while opening: $!"; |
106 |
|
107 |
# stat'ing filehandles is generally non-blocking |
108 |
my $size = -s $fh; |
109 |
|
110 |
# queue a request to read the file |
111 |
my $contents; |
112 |
aio_read $fh, 0, $size, $contents, 0, sub { |
113 |
$_[0] == $size |
114 |
or die "short read: $!"; |
115 |
|
116 |
close $fh; |
117 |
|
118 |
# file contents now in $contents |
119 |
print $contents; |
120 |
|
121 |
# exit event loop and program |
122 |
Event::unloop; |
123 |
}; |
124 |
}; |
125 |
|
126 |
# possibly queue up other requests, or open GUI windows, |
127 |
# check for sockets etc. etc. |
128 |
|
129 |
# process events as long as there are some: |
130 |
Event::loop; |
131 |
|
132 |
=head1 REQUEST ANATOMY AND LIFETIME |
133 |
|
134 |
Every C<aio_*> function creates a request. which is a C data structure not |
135 |
directly visible to Perl. |
136 |
|
137 |
If called in non-void context, every request function returns a Perl |
138 |
object representing the request. In void context, nothing is returned, |
139 |
which saves a bit of memory. |
140 |
|
141 |
The perl object is a fairly standard ref-to-hash object. The hash contents |
142 |
are not used by IO::AIO so you are free to store anything you like in it. |
143 |
|
144 |
During their existance, aio requests travel through the following states, |
145 |
in order: |
146 |
|
147 |
=over 4 |
148 |
|
149 |
=item ready |
150 |
|
151 |
Immediately after a request is created it is put into the ready state, |
152 |
waiting for a thread to execute it. |
153 |
|
154 |
=item execute |
155 |
|
156 |
A thread has accepted the request for processing and is currently |
157 |
executing it (e.g. blocking in read). |
158 |
|
159 |
=item pending |
160 |
|
161 |
The request has been executed and is waiting for result processing. |
162 |
|
163 |
While request submission and execution is fully asynchronous, result |
164 |
processing is not and relies on the perl interpreter calling C<poll_cb> |
165 |
(or another function with the same effect). |
166 |
|
167 |
=item result |
168 |
|
169 |
The request results are processed synchronously by C<poll_cb>. |
170 |
|
171 |
The C<poll_cb> function will process all outstanding aio requests by |
172 |
calling their callbacks, freeing memory associated with them and managing |
173 |
any groups they are contained in. |
174 |
|
175 |
=item done |
176 |
|
177 |
Request has reached the end of its lifetime and holds no resources anymore |
178 |
(except possibly for the Perl object, but its connection to the actual |
179 |
aio request is severed and calling its methods will either do nothing or |
180 |
result in a runtime error). |
181 |
|
182 |
=back |
183 |
|
184 |
=cut |
185 |
|
186 |
package IO::AIO; |
187 |
|
188 |
use Carp (); |
189 |
|
190 |
no warnings; |
191 |
use strict 'vars'; |
192 |
|
193 |
use base 'Exporter'; |
194 |
|
195 |
BEGIN { |
196 |
our $VERSION = '2.51'; |
197 |
|
198 |
our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat |
199 |
aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink |
200 |
aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link |
201 |
aio_move aio_copy aio_group aio_nop aio_mknod aio_load aio_rmtree aio_mkdir |
202 |
aio_chown aio_chmod aio_utime aio_truncate); |
203 |
our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice aio_block)); |
204 |
our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush |
205 |
min_parallel max_parallel max_idle |
206 |
nreqs nready npending nthreads |
207 |
max_poll_time max_poll_reqs); |
208 |
|
209 |
@IO::AIO::GRP::ISA = 'IO::AIO::REQ'; |
210 |
|
211 |
require XSLoader; |
212 |
XSLoader::load ("IO::AIO", $VERSION); |
213 |
} |
214 |
|
215 |
=head1 FUNCTIONS |
216 |
|
217 |
=head2 AIO REQUEST FUNCTIONS |
218 |
|
219 |
All the C<aio_*> calls are more or less thin wrappers around the syscall |
220 |
with the same name (sans C<aio_>). The arguments are similar or identical, |
221 |
and they all accept an additional (and optional) C<$callback> argument |
222 |
which must be a code reference. This code reference will get called with |
223 |
the syscall return code (e.g. most syscalls return C<-1> on error, unlike |
224 |
perl, which usually delivers "false") as it's sole argument when the given |
225 |
syscall has been executed asynchronously. |
226 |
|
227 |
All functions expecting a filehandle keep a copy of the filehandle |
228 |
internally until the request has finished. |
229 |
|
230 |
All functions return request objects of type L<IO::AIO::REQ> that allow |
231 |
further manipulation of those requests while they are in-flight. |
232 |
|
233 |
The pathnames you pass to these routines I<must> be absolute and |
234 |
encoded as octets. The reason for the former is that at the time the |
235 |
request is being executed, the current working directory could have |
236 |
changed. Alternatively, you can make sure that you never change the |
237 |
current working directory anywhere in the program and then use relative |
238 |
paths. |
239 |
|
240 |
To encode pathnames as octets, either make sure you either: a) always pass |
241 |
in filenames you got from outside (command line, readdir etc.) without |
242 |
tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode |
243 |
your pathnames to the locale (or other) encoding in effect in the user |
244 |
environment, d) use Glib::filename_from_unicode on unicode filenames or e) |
245 |
use something else to ensure your scalar has the correct contents. |
246 |
|
247 |
This works, btw. independent of the internal UTF-8 bit, which IO::AIO |
248 |
handles correctly wether it is set or not. |
249 |
|
250 |
=over 4 |
251 |
|
252 |
=item $prev_pri = aioreq_pri [$pri] |
253 |
|
254 |
Returns the priority value that would be used for the next request and, if |
255 |
C<$pri> is given, sets the priority for the next aio request. |
256 |
|
257 |
The default priority is C<0>, the minimum and maximum priorities are C<-4> |
258 |
and C<4>, respectively. Requests with higher priority will be serviced |
259 |
first. |
260 |
|
261 |
The priority will be reset to C<0> after each call to one of the C<aio_*> |
262 |
functions. |
263 |
|
264 |
Example: open a file with low priority, then read something from it with |
265 |
higher priority so the read request is serviced before other low priority |
266 |
open requests (potentially spamming the cache): |
267 |
|
268 |
aioreq_pri -3; |
269 |
aio_open ..., sub { |
270 |
return unless $_[0]; |
271 |
|
272 |
aioreq_pri -2; |
273 |
aio_read $_[0], ..., sub { |
274 |
... |
275 |
}; |
276 |
}; |
277 |
|
278 |
|
279 |
=item aioreq_nice $pri_adjust |
280 |
|
281 |
Similar to C<aioreq_pri>, but subtracts the given value from the current |
282 |
priority, so the effect is cumulative. |
283 |
|
284 |
|
285 |
=item aio_open $pathname, $flags, $mode, $callback->($fh) |
286 |
|
287 |
Asynchronously open or create a file and call the callback with a newly |
288 |
created filehandle for the file. |
289 |
|
290 |
The pathname passed to C<aio_open> must be absolute. See API NOTES, above, |
291 |
for an explanation. |
292 |
|
293 |
The C<$flags> argument is a bitmask. See the C<Fcntl> module for a |
294 |
list. They are the same as used by C<sysopen>. |
295 |
|
296 |
Likewise, C<$mode> specifies the mode of the newly created file, if it |
297 |
didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>, |
298 |
except that it is mandatory (i.e. use C<0> if you don't create new files, |
299 |
and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified |
300 |
by the umask in effect then the request is being executed, so better never |
301 |
change the umask. |
302 |
|
303 |
Example: |
304 |
|
305 |
aio_open "/etc/passwd", O_RDONLY, 0, sub { |
306 |
if ($_[0]) { |
307 |
print "open successful, fh is $_[0]\n"; |
308 |
... |
309 |
} else { |
310 |
die "open failed: $!\n"; |
311 |
} |
312 |
}; |
313 |
|
314 |
|
315 |
=item aio_close $fh, $callback->($status) |
316 |
|
317 |
Asynchronously close a file and call the callback with the result |
318 |
code. |
319 |
|
320 |
Unfortunately, you can't do this to perl. Perl I<insists> very strongly on |
321 |
closing the file descriptor associated with the filehandle itself. Here is |
322 |
what aio_close will try: |
323 |
|
324 |
1. dup()licate the fd |
325 |
2. asynchronously close() the duplicated fd |
326 |
3. dup()licate the fd once more |
327 |
4. let perl close() the filehandle |
328 |
5. asynchronously close the duplicated fd |
329 |
|
330 |
The idea is that the first close() flushes stuff to disk that closing an |
331 |
fd will flush, so when perl closes the fd, nothing much will need to be |
332 |
flushed. The second async. close() will then flush stuff to disk that |
333 |
closing the last fd to the file will flush. |
334 |
|
335 |
Just FYI, SuSv3 has this to say on close: |
336 |
|
337 |
All outstanding record locks owned by the process on the file |
338 |
associated with the file descriptor shall be removed. |
339 |
|
340 |
If fildes refers to a socket, close() shall cause the socket to be |
341 |
destroyed. ... close() shall block for up to the current linger |
342 |
interval until all data is transmitted. |
343 |
[this actually sounds like a specification bug, but who knows] |
344 |
|
345 |
And at least Linux additionally actually flushes stuff on every close, |
346 |
even when the file itself is still open. |
347 |
|
348 |
Sounds enourmously inefficient and complicated? Yes... please show me how |
349 |
to nuke perl's fd out of existence... |
350 |
|
351 |
=cut |
352 |
|
353 |
sub aio_close($;$) { |
354 |
aio_block { |
355 |
my ($fh, $cb) = @_; |
356 |
|
357 |
my $pri = aioreq_pri; |
358 |
my $grp = aio_group $cb; |
359 |
|
360 |
my $fd = fileno $fh; |
361 |
|
362 |
defined $fd or Carp::croak "aio_close called with fd-less filehandle"; |
363 |
|
364 |
# if the dups fail we will simply get EBADF |
365 |
my $fd2 = _dup $fd; |
366 |
aioreq_pri $pri; |
367 |
add $grp _aio_close $fd2, sub { |
368 |
my $fd2 = _dup $fd; |
369 |
close $fh; |
370 |
aioreq_pri $pri; |
371 |
add $grp _aio_close $fd2, sub { |
372 |
$grp->result ($_[0]); |
373 |
}; |
374 |
}; |
375 |
|
376 |
$grp |
377 |
} |
378 |
} |
379 |
|
380 |
|
381 |
=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) |
382 |
|
383 |
=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) |
384 |
|
385 |
Reads or writes C<$length> bytes from the specified C<$fh> and C<$offset> |
386 |
into the scalar given by C<$data> and offset C<$dataoffset> and calls the |
387 |
callback without the actual number of bytes read (or -1 on error, just |
388 |
like the syscall). |
389 |
|
390 |
If C<$offset> is undefined, then the current file descriptor offset will |
391 |
be used (and updated), otherwise the file descriptor offset will not be |
392 |
changed by these calls. |
393 |
|
394 |
If C<$length> is undefined in C<aio_write>, use the remaining length of C<$data>. |
395 |
|
396 |
If C<$dataoffset> is less than zero, it will be counted from the end of |
397 |
C<$data>. |
398 |
|
399 |
The C<$data> scalar I<MUST NOT> be modified in any way while the request |
400 |
is outstanding. Modifying it can result in segfaults or World War III (if |
401 |
the necessary/optional hardware is installed). |
402 |
|
403 |
Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at |
404 |
offset C<0> within the scalar: |
405 |
|
406 |
aio_read $fh, 7, 15, $buffer, 0, sub { |
407 |
$_[0] > 0 or die "read error: $!"; |
408 |
print "read $_[0] bytes: <$buffer>\n"; |
409 |
}; |
410 |
|
411 |
|
412 |
=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) |
413 |
|
414 |
Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts |
415 |
reading at byte offset C<$in_offset>, and starts writing at the current |
416 |
file offset of C<$out_fh>. Because of that, it is not safe to issue more |
417 |
than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each |
418 |
other. |
419 |
|
420 |
This call tries to make use of a native C<sendfile> syscall to provide |
421 |
zero-copy operation. For this to work, C<$out_fh> should refer to a |
422 |
socket, and C<$in_fh> should refer to mmap'able file. |
423 |
|
424 |
If the native sendfile call fails or is not implemented, it will be |
425 |
emulated, so you can call C<aio_sendfile> on any type of filehandle |
426 |
regardless of the limitations of the operating system. |
427 |
|
428 |
Please note, however, that C<aio_sendfile> can read more bytes from |
429 |
C<$in_fh> than are written, and there is no way to find out how many |
430 |
bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only |
431 |
provides the number of bytes written to C<$out_fh>. Only if the result |
432 |
value equals C<$length> one can assume that C<$length> bytes have been |
433 |
read. |
434 |
|
435 |
|
436 |
=item aio_readahead $fh,$offset,$length, $callback->($retval) |
437 |
|
438 |
C<aio_readahead> populates the page cache with data from a file so that |
439 |
subsequent reads from that file will not block on disk I/O. The C<$offset> |
440 |
argument specifies the starting point from which data is to be read and |
441 |
C<$length> specifies the number of bytes to be read. I/O is performed in |
442 |
whole pages, so that offset is effectively rounded down to a page boundary |
443 |
and bytes are read up to the next page boundary greater than or equal to |
444 |
(off-set+length). C<aio_readahead> does not read beyond the end of the |
445 |
file. The current file offset of the file is left unchanged. |
446 |
|
447 |
If that syscall doesn't exist (likely if your OS isn't Linux) it will be |
448 |
emulated by simply reading the data, which would have a similar effect. |
449 |
|
450 |
|
451 |
=item aio_stat $fh_or_path, $callback->($status) |
452 |
|
453 |
=item aio_lstat $fh, $callback->($status) |
454 |
|
455 |
Works like perl's C<stat> or C<lstat> in void context. The callback will |
456 |
be called after the stat and the results will be available using C<stat _> |
457 |
or C<-s _> etc... |
458 |
|
459 |
The pathname passed to C<aio_stat> must be absolute. See API NOTES, above, |
460 |
for an explanation. |
461 |
|
462 |
Currently, the stats are always 64-bit-stats, i.e. instead of returning an |
463 |
error when stat'ing a large file, the results will be silently truncated |
464 |
unless perl itself is compiled with large file support. |
465 |
|
466 |
Example: Print the length of F</etc/passwd>: |
467 |
|
468 |
aio_stat "/etc/passwd", sub { |
469 |
$_[0] and die "stat failed: $!"; |
470 |
print "size is ", -s _, "\n"; |
471 |
}; |
472 |
|
473 |
|
474 |
=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status) |
475 |
|
476 |
Works like perl's C<utime> function (including the special case of $atime |
477 |
and $mtime being undef). Fractional times are supported if the underlying |
478 |
syscalls support them. |
479 |
|
480 |
When called with a pathname, uses utimes(2) if available, otherwise |
481 |
utime(2). If called on a file descriptor, uses futimes(2) if available, |
482 |
otherwise returns ENOSYS, so this is not portable. |
483 |
|
484 |
Examples: |
485 |
|
486 |
# set atime and mtime to current time (basically touch(1)): |
487 |
aio_utime "path", undef, undef; |
488 |
# set atime to current time and mtime to beginning of the epoch: |
489 |
aio_utime "path", time, undef; # undef==0 |
490 |
|
491 |
|
492 |
=item aio_chown $fh_or_path, $uid, $gid, $callback->($status) |
493 |
|
494 |
Works like perl's C<chown> function, except that C<undef> for either $uid |
495 |
or $gid is being interpreted as "do not change" (but -1 can also be used). |
496 |
|
497 |
Examples: |
498 |
|
499 |
# same as "chown root path" in the shell: |
500 |
aio_chown "path", 0, -1; |
501 |
# same as above: |
502 |
aio_chown "path", 0, undef; |
503 |
|
504 |
|
505 |
=item aio_truncate $fh_or_path, $offset, $callback->($status) |
506 |
|
507 |
Works like truncate(2) or ftruncate(2). |
508 |
|
509 |
|
510 |
=item aio_chmod $fh_or_path, $mode, $callback->($status) |
511 |
|
512 |
Works like perl's C<chmod> function. |
513 |
|
514 |
|
515 |
=item aio_unlink $pathname, $callback->($status) |
516 |
|
517 |
Asynchronously unlink (delete) a file and call the callback with the |
518 |
result code. |
519 |
|
520 |
|
521 |
=item aio_mknod $path, $mode, $dev, $callback->($status) |
522 |
|
523 |
[EXPERIMENTAL] |
524 |
|
525 |
Asynchronously create a device node (or fifo). See mknod(2). |
526 |
|
527 |
The only (POSIX-) portable way of calling this function is: |
528 |
|
529 |
aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... |
530 |
|
531 |
|
532 |
=item aio_link $srcpath, $dstpath, $callback->($status) |
533 |
|
534 |
Asynchronously create a new link to the existing object at C<$srcpath> at |
535 |
the path C<$dstpath> and call the callback with the result code. |
536 |
|
537 |
|
538 |
=item aio_symlink $srcpath, $dstpath, $callback->($status) |
539 |
|
540 |
Asynchronously create a new symbolic link to the existing object at C<$srcpath> at |
541 |
the path C<$dstpath> and call the callback with the result code. |
542 |
|
543 |
|
544 |
=item aio_readlink $path, $callback->($link) |
545 |
|
546 |
Asynchronously read the symlink specified by C<$path> and pass it to |
547 |
the callback. If an error occurs, nothing or undef gets passed to the |
548 |
callback. |
549 |
|
550 |
|
551 |
=item aio_rename $srcpath, $dstpath, $callback->($status) |
552 |
|
553 |
Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as |
554 |
rename(2) and call the callback with the result code. |
555 |
|
556 |
|
557 |
=item aio_mkdir $pathname, $mode, $callback->($status) |
558 |
|
559 |
Asynchronously mkdir (create) a directory and call the callback with |
560 |
the result code. C<$mode> will be modified by the umask at the time the |
561 |
request is executed, so do not change your umask. |
562 |
|
563 |
|
564 |
=item aio_rmdir $pathname, $callback->($status) |
565 |
|
566 |
Asynchronously rmdir (delete) a directory and call the callback with the |
567 |
result code. |
568 |
|
569 |
|
570 |
=item aio_readdir $pathname, $callback->($entries) |
571 |
|
572 |
Unlike the POSIX call of the same name, C<aio_readdir> reads an entire |
573 |
directory (i.e. opendir + readdir + closedir). The entries will not be |
574 |
sorted, and will B<NOT> include the C<.> and C<..> entries. |
575 |
|
576 |
The callback a single argument which is either C<undef> or an array-ref |
577 |
with the filenames. |
578 |
|
579 |
|
580 |
=item aio_load $path, $data, $callback->($status) |
581 |
|
582 |
This is a composite request that tries to fully load the given file into |
583 |
memory. Status is the same as with aio_read. |
584 |
|
585 |
=cut |
586 |
|
587 |
sub aio_load($$;$) { |
588 |
aio_block { |
589 |
my ($path, undef, $cb) = @_; |
590 |
my $data = \$_[1]; |
591 |
|
592 |
my $pri = aioreq_pri; |
593 |
my $grp = aio_group $cb; |
594 |
|
595 |
aioreq_pri $pri; |
596 |
add $grp aio_open $path, O_RDONLY, 0, sub { |
597 |
my $fh = shift |
598 |
or return $grp->result (-1); |
599 |
|
600 |
aioreq_pri $pri; |
601 |
add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub { |
602 |
$grp->result ($_[0]); |
603 |
}; |
604 |
}; |
605 |
|
606 |
$grp |
607 |
} |
608 |
} |
609 |
|
610 |
=item aio_copy $srcpath, $dstpath, $callback->($status) |
611 |
|
612 |
Try to copy the I<file> (directories not supported as either source or |
613 |
destination) from C<$srcpath> to C<$dstpath> and call the callback with |
614 |
the C<0> (error) or C<-1> ok. |
615 |
|
616 |
This is a composite request that it creates the destination file with |
617 |
mode 0200 and copies the contents of the source file into it using |
618 |
C<aio_sendfile>, followed by restoring atime, mtime, access mode and |
619 |
uid/gid, in that order. |
620 |
|
621 |
If an error occurs, the partial destination file will be unlinked, if |
622 |
possible, except when setting atime, mtime, access mode and uid/gid, where |
623 |
errors are being ignored. |
624 |
|
625 |
=cut |
626 |
|
627 |
sub aio_copy($$;$) { |
628 |
aio_block { |
629 |
my ($src, $dst, $cb) = @_; |
630 |
|
631 |
my $pri = aioreq_pri; |
632 |
my $grp = aio_group $cb; |
633 |
|
634 |
aioreq_pri $pri; |
635 |
add $grp aio_open $src, O_RDONLY, 0, sub { |
636 |
if (my $src_fh = $_[0]) { |
637 |
my @stat = stat $src_fh; |
638 |
|
639 |
aioreq_pri $pri; |
640 |
add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub { |
641 |
if (my $dst_fh = $_[0]) { |
642 |
aioreq_pri $pri; |
643 |
add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub { |
644 |
if ($_[0] == $stat[7]) { |
645 |
$grp->result (0); |
646 |
close $src_fh; |
647 |
|
648 |
# those should not normally block. should. should. |
649 |
utime $stat[8], $stat[9], $dst; |
650 |
chmod $stat[2] & 07777, $dst_fh; |
651 |
chown $stat[4], $stat[5], $dst_fh; |
652 |
close $dst_fh; |
653 |
} else { |
654 |
$grp->result (-1); |
655 |
close $src_fh; |
656 |
close $dst_fh; |
657 |
|
658 |
aioreq $pri; |
659 |
add $grp aio_unlink $dst; |
660 |
} |
661 |
}; |
662 |
} else { |
663 |
$grp->result (-1); |
664 |
} |
665 |
}, |
666 |
|
667 |
} else { |
668 |
$grp->result (-1); |
669 |
} |
670 |
}; |
671 |
|
672 |
$grp |
673 |
} |
674 |
} |
675 |
|
676 |
=item aio_move $srcpath, $dstpath, $callback->($status) |
677 |
|
678 |
Try to move the I<file> (directories not supported as either source or |
679 |
destination) from C<$srcpath> to C<$dstpath> and call the callback with |
680 |
the C<0> (error) or C<-1> ok. |
681 |
|
682 |
This is a composite request that tries to rename(2) the file first. If |
683 |
rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if |
684 |
that is successful, unlinking the C<$srcpath>. |
685 |
|
686 |
=cut |
687 |
|
688 |
sub aio_move($$;$) { |
689 |
aio_block { |
690 |
my ($src, $dst, $cb) = @_; |
691 |
|
692 |
my $pri = aioreq_pri; |
693 |
my $grp = aio_group $cb; |
694 |
|
695 |
aioreq_pri $pri; |
696 |
add $grp aio_rename $src, $dst, sub { |
697 |
if ($_[0] && $! == EXDEV) { |
698 |
aioreq_pri $pri; |
699 |
add $grp aio_copy $src, $dst, sub { |
700 |
$grp->result ($_[0]); |
701 |
|
702 |
if (!$_[0]) { |
703 |
aioreq_pri $pri; |
704 |
add $grp aio_unlink $src; |
705 |
} |
706 |
}; |
707 |
} else { |
708 |
$grp->result ($_[0]); |
709 |
} |
710 |
}; |
711 |
|
712 |
$grp |
713 |
} |
714 |
} |
715 |
|
716 |
=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) |
717 |
|
718 |
Scans a directory (similar to C<aio_readdir>) but additionally tries to |
719 |
efficiently separate the entries of directory C<$path> into two sets of |
720 |
names, directories you can recurse into (directories), and ones you cannot |
721 |
recurse into (everything else, including symlinks to directories). |
722 |
|
723 |
C<aio_scandir> is a composite request that creates of many sub requests_ |
724 |
C<$maxreq> specifies the maximum number of outstanding aio requests that |
725 |
this function generates. If it is C<< <= 0 >>, then a suitable default |
726 |
will be chosen (currently 4). |
727 |
|
728 |
On error, the callback is called without arguments, otherwise it receives |
729 |
two array-refs with path-relative entry names. |
730 |
|
731 |
Example: |
732 |
|
733 |
aio_scandir $dir, 0, sub { |
734 |
my ($dirs, $nondirs) = @_; |
735 |
print "real directories: @$dirs\n"; |
736 |
print "everything else: @$nondirs\n"; |
737 |
}; |
738 |
|
739 |
Implementation notes. |
740 |
|
741 |
The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can. |
742 |
|
743 |
After reading the directory, the modification time, size etc. of the |
744 |
directory before and after the readdir is checked, and if they match (and |
745 |
isn't the current time), the link count will be used to decide how many |
746 |
entries are directories (if >= 2). Otherwise, no knowledge of the number |
747 |
of subdirectories will be assumed. |
748 |
|
749 |
Then entries will be sorted into likely directories (everything without |
750 |
a non-initial dot currently) and likely non-directories (everything |
751 |
else). Then every entry plus an appended C</.> will be C<stat>'ed, |
752 |
likely directories first. If that succeeds, it assumes that the entry |
753 |
is a directory or a symlink to directory (which will be checked |
754 |
seperately). This is often faster than stat'ing the entry itself because |
755 |
filesystems might detect the type of the entry without reading the inode |
756 |
data (e.g. ext2fs filetype feature). |
757 |
|
758 |
If the known number of directories (link count - 2) has been reached, the |
759 |
rest of the entries is assumed to be non-directories. |
760 |
|
761 |
This only works with certainty on POSIX (= UNIX) filesystems, which |
762 |
fortunately are the vast majority of filesystems around. |
763 |
|
764 |
It will also likely work on non-POSIX filesystems with reduced efficiency |
765 |
as those tend to return 0 or 1 as link counts, which disables the |
766 |
directory counting heuristic. |
767 |
|
768 |
=cut |
769 |
|
770 |
sub aio_scandir($$;$) { |
771 |
aio_block { |
772 |
my ($path, $maxreq, $cb) = @_; |
773 |
|
774 |
my $pri = aioreq_pri; |
775 |
|
776 |
my $grp = aio_group $cb; |
777 |
|
778 |
$maxreq = 4 if $maxreq <= 0; |
779 |
|
780 |
# stat once |
781 |
aioreq_pri $pri; |
782 |
add $grp aio_stat $path, sub { |
783 |
return $grp->result () if $_[0]; |
784 |
my $now = time; |
785 |
my $hash1 = join ":", (stat _)[0,1,3,7,9]; |
786 |
|
787 |
# read the directory entries |
788 |
aioreq_pri $pri; |
789 |
add $grp aio_readdir $path, sub { |
790 |
my $entries = shift |
791 |
or return $grp->result (); |
792 |
|
793 |
# stat the dir another time |
794 |
aioreq_pri $pri; |
795 |
add $grp aio_stat $path, sub { |
796 |
my $hash2 = join ":", (stat _)[0,1,3,7,9]; |
797 |
|
798 |
my $ndirs; |
799 |
|
800 |
# take the slow route if anything looks fishy |
801 |
if ($hash1 ne $hash2 or (stat _)[9] == $now) { |
802 |
$ndirs = -1; |
803 |
} else { |
804 |
# if nlink == 2, we are finished |
805 |
# on non-posix-fs's, we rely on nlink < 2 |
806 |
$ndirs = (stat _)[3] - 2 |
807 |
or return $grp->result ([], $entries); |
808 |
} |
809 |
|
810 |
# sort into likely dirs and likely nondirs |
811 |
# dirs == files without ".", short entries first |
812 |
$entries = [map $_->[0], |
813 |
sort { $b->[1] cmp $a->[1] } |
814 |
map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length], |
815 |
@$entries]; |
816 |
|
817 |
my (@dirs, @nondirs); |
818 |
|
819 |
my $statgrp = add $grp aio_group sub { |
820 |
$grp->result (\@dirs, \@nondirs); |
821 |
}; |
822 |
|
823 |
limit $statgrp $maxreq; |
824 |
feed $statgrp sub { |
825 |
return unless @$entries; |
826 |
my $entry = pop @$entries; |
827 |
|
828 |
aioreq_pri $pri; |
829 |
add $statgrp aio_stat "$path/$entry/.", sub { |
830 |
if ($_[0] < 0) { |
831 |
push @nondirs, $entry; |
832 |
} else { |
833 |
# need to check for real directory |
834 |
aioreq_pri $pri; |
835 |
add $statgrp aio_lstat "$path/$entry", sub { |
836 |
if (-d _) { |
837 |
push @dirs, $entry; |
838 |
|
839 |
unless (--$ndirs) { |
840 |
push @nondirs, @$entries; |
841 |
feed $statgrp; |
842 |
} |
843 |
} else { |
844 |
push @nondirs, $entry; |
845 |
} |
846 |
} |
847 |
} |
848 |
}; |
849 |
}; |
850 |
}; |
851 |
}; |
852 |
}; |
853 |
|
854 |
$grp |
855 |
} |
856 |
} |
857 |
|
858 |
=item aio_rmtree $path, $callback->($status) |
859 |
|
860 |
Delete a directory tree starting (and including) C<$path>, return the |
861 |
status of the final C<rmdir> only. This is a composite request that |
862 |
uses C<aio_scandir> to recurse into and rmdir directories, and unlink |
863 |
everything else. |
864 |
|
865 |
=cut |
866 |
|
867 |
sub aio_rmtree; |
868 |
sub aio_rmtree($;$) { |
869 |
aio_block { |
870 |
my ($path, $cb) = @_; |
871 |
|
872 |
my $pri = aioreq_pri; |
873 |
my $grp = aio_group $cb; |
874 |
|
875 |
aioreq_pri $pri; |
876 |
add $grp aio_scandir $path, 0, sub { |
877 |
my ($dirs, $nondirs) = @_; |
878 |
|
879 |
my $dirgrp = aio_group sub { |
880 |
add $grp aio_rmdir $path, sub { |
881 |
$grp->result ($_[0]); |
882 |
}; |
883 |
}; |
884 |
|
885 |
(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs; |
886 |
(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs; |
887 |
|
888 |
add $grp $dirgrp; |
889 |
}; |
890 |
|
891 |
$grp |
892 |
} |
893 |
} |
894 |
|
895 |
=item aio_fsync $fh, $callback->($status) |
896 |
|
897 |
Asynchronously call fsync on the given filehandle and call the callback |
898 |
with the fsync result code. |
899 |
|
900 |
=item aio_fdatasync $fh, $callback->($status) |
901 |
|
902 |
Asynchronously call fdatasync on the given filehandle and call the |
903 |
callback with the fdatasync result code. |
904 |
|
905 |
If this call isn't available because your OS lacks it or it couldn't be |
906 |
detected, it will be emulated by calling C<fsync> instead. |
907 |
|
908 |
=item aio_group $callback->(...) |
909 |
|
910 |
This is a very special aio request: Instead of doing something, it is a |
911 |
container for other aio requests, which is useful if you want to bundle |
912 |
many requests into a single, composite, request with a definite callback |
913 |
and the ability to cancel the whole request with its subrequests. |
914 |
|
915 |
Returns an object of class L<IO::AIO::GRP>. See its documentation below |
916 |
for more info. |
917 |
|
918 |
Example: |
919 |
|
920 |
my $grp = aio_group sub { |
921 |
print "all stats done\n"; |
922 |
}; |
923 |
|
924 |
add $grp |
925 |
(aio_stat ...), |
926 |
(aio_stat ...), |
927 |
...; |
928 |
|
929 |
=item aio_nop $callback->() |
930 |
|
931 |
This is a special request - it does nothing in itself and is only used for |
932 |
side effects, such as when you want to add a dummy request to a group so |
933 |
that finishing the requests in the group depends on executing the given |
934 |
code. |
935 |
|
936 |
While this request does nothing, it still goes through the execution |
937 |
phase and still requires a worker thread. Thus, the callback will not |
938 |
be executed immediately but only after other requests in the queue have |
939 |
entered their execution phase. This can be used to measure request |
940 |
latency. |
941 |
|
942 |
=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED* |
943 |
|
944 |
Mainly used for debugging and benchmarking, this aio request puts one of |
945 |
the request workers to sleep for the given time. |
946 |
|
947 |
While it is theoretically handy to have simple I/O scheduling requests |
948 |
like sleep and file handle readable/writable, the overhead this creates is |
949 |
immense (it blocks a thread for a long time) so do not use this function |
950 |
except to put your application under artificial I/O pressure. |
951 |
|
952 |
=back |
953 |
|
954 |
=head2 IO::AIO::REQ CLASS |
955 |
|
956 |
All non-aggregate C<aio_*> functions return an object of this class when |
957 |
called in non-void context. |
958 |
|
959 |
=over 4 |
960 |
|
961 |
=item cancel $req |
962 |
|
963 |
Cancels the request, if possible. Has the effect of skipping execution |
964 |
when entering the B<execute> state and skipping calling the callback when |
965 |
entering the the B<result> state, but will leave the request otherwise |
966 |
untouched. That means that requests that currently execute will not be |
967 |
stopped and resources held by the request will not be freed prematurely. |
968 |
|
969 |
=item cb $req $callback->(...) |
970 |
|
971 |
Replace (or simply set) the callback registered to the request. |
972 |
|
973 |
=back |
974 |
|
975 |
=head2 IO::AIO::GRP CLASS |
976 |
|
977 |
This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to |
978 |
objects of this class, too. |
979 |
|
980 |
A IO::AIO::GRP object is a special request that can contain multiple other |
981 |
aio requests. |
982 |
|
983 |
You create one by calling the C<aio_group> constructing function with a |
984 |
callback that will be called when all contained requests have entered the |
985 |
C<done> state: |
986 |
|
987 |
my $grp = aio_group sub { |
988 |
print "all requests are done\n"; |
989 |
}; |
990 |
|
991 |
You add requests by calling the C<add> method with one or more |
992 |
C<IO::AIO::REQ> objects: |
993 |
|
994 |
$grp->add (aio_unlink "..."); |
995 |
|
996 |
add $grp aio_stat "...", sub { |
997 |
$_[0] or return $grp->result ("error"); |
998 |
|
999 |
# add another request dynamically, if first succeeded |
1000 |
add $grp aio_open "...", sub { |
1001 |
$grp->result ("ok"); |
1002 |
}; |
1003 |
}; |
1004 |
|
1005 |
This makes it very easy to create composite requests (see the source of |
1006 |
C<aio_move> for an application) that work and feel like simple requests. |
1007 |
|
1008 |
=over 4 |
1009 |
|
1010 |
=item * The IO::AIO::GRP objects will be cleaned up during calls to |
1011 |
C<IO::AIO::poll_cb>, just like any other request. |
1012 |
|
1013 |
=item * They can be canceled like any other request. Canceling will cancel not |
1014 |
only the request itself, but also all requests it contains. |
1015 |
|
1016 |
=item * They can also can also be added to other IO::AIO::GRP objects. |
1017 |
|
1018 |
=item * You must not add requests to a group from within the group callback (or |
1019 |
any later time). |
1020 |
|
1021 |
=back |
1022 |
|
1023 |
Their lifetime, simplified, looks like this: when they are empty, they |
1024 |
will finish very quickly. If they contain only requests that are in the |
1025 |
C<done> state, they will also finish. Otherwise they will continue to |
1026 |
exist. |
1027 |
|
1028 |
That means after creating a group you have some time to add requests. And |
1029 |
in the callbacks of those requests, you can add further requests to the |
1030 |
group. And only when all those requests have finished will the the group |
1031 |
itself finish. |
1032 |
|
1033 |
=over 4 |
1034 |
|
1035 |
=item add $grp ... |
1036 |
|
1037 |
=item $grp->add (...) |
1038 |
|
1039 |
Add one or more requests to the group. Any type of L<IO::AIO::REQ> can |
1040 |
be added, including other groups, as long as you do not create circular |
1041 |
dependencies. |
1042 |
|
1043 |
Returns all its arguments. |
1044 |
|
1045 |
=item $grp->cancel_subs |
1046 |
|
1047 |
Cancel all subrequests and clears any feeder, but not the group request |
1048 |
itself. Useful when you queued a lot of events but got a result early. |
1049 |
|
1050 |
=item $grp->result (...) |
1051 |
|
1052 |
Set the result value(s) that will be passed to the group callback when all |
1053 |
subrequests have finished and set thre groups errno to the current value |
1054 |
of errno (just like calling C<errno> without an error number). By default, |
1055 |
no argument will be passed and errno is zero. |
1056 |
|
1057 |
=item $grp->errno ([$errno]) |
1058 |
|
1059 |
Sets the group errno value to C<$errno>, or the current value of errno |
1060 |
when the argument is missing. |
1061 |
|
1062 |
Every aio request has an associated errno value that is restored when |
1063 |
the callback is invoked. This method lets you change this value from its |
1064 |
default (0). |
1065 |
|
1066 |
Calling C<result> will also set errno, so make sure you either set C<$!> |
1067 |
before the call to C<result>, or call c<errno> after it. |
1068 |
|
1069 |
=item feed $grp $callback->($grp) |
1070 |
|
1071 |
Sets a feeder/generator on this group: every group can have an attached |
1072 |
generator that generates requests if idle. The idea behind this is that, |
1073 |
although you could just queue as many requests as you want in a group, |
1074 |
this might starve other requests for a potentially long time. For |
1075 |
example, C<aio_scandir> might generate hundreds of thousands C<aio_stat> |
1076 |
requests, delaying any later requests for a long time. |
1077 |
|
1078 |
To avoid this, and allow incremental generation of requests, you can |
1079 |
instead a group and set a feeder on it that generates those requests. The |
1080 |
feed callback will be called whenever there are few enough (see C<limit>, |
1081 |
below) requests active in the group itself and is expected to queue more |
1082 |
requests. |
1083 |
|
1084 |
The feed callback can queue as many requests as it likes (i.e. C<add> does |
1085 |
not impose any limits). |
1086 |
|
1087 |
If the feed does not queue more requests when called, it will be |
1088 |
automatically removed from the group. |
1089 |
|
1090 |
If the feed limit is C<0>, it will be set to C<2> automatically. |
1091 |
|
1092 |
Example: |
1093 |
|
1094 |
# stat all files in @files, but only ever use four aio requests concurrently: |
1095 |
|
1096 |
my $grp = aio_group sub { print "finished\n" }; |
1097 |
limit $grp 4; |
1098 |
feed $grp sub { |
1099 |
my $file = pop @files |
1100 |
or return; |
1101 |
|
1102 |
add $grp aio_stat $file, sub { ... }; |
1103 |
}; |
1104 |
|
1105 |
=item limit $grp $num |
1106 |
|
1107 |
Sets the feeder limit for the group: The feeder will be called whenever |
1108 |
the group contains less than this many requests. |
1109 |
|
1110 |
Setting the limit to C<0> will pause the feeding process. |
1111 |
|
1112 |
=back |
1113 |
|
1114 |
=head2 SUPPORT FUNCTIONS |
1115 |
|
1116 |
=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION |
1117 |
|
1118 |
=over 4 |
1119 |
|
1120 |
=item $fileno = IO::AIO::poll_fileno |
1121 |
|
1122 |
Return the I<request result pipe file descriptor>. This filehandle must be |
1123 |
polled for reading by some mechanism outside this module (e.g. Event or |
1124 |
select, see below or the SYNOPSIS). If the pipe becomes readable you have |
1125 |
to call C<poll_cb> to check the results. |
1126 |
|
1127 |
See C<poll_cb> for an example. |
1128 |
|
1129 |
=item IO::AIO::poll_cb |
1130 |
|
1131 |
Process some outstanding events on the result pipe. You have to call this |
1132 |
regularly. Returns the number of events processed. Returns immediately |
1133 |
when no events are outstanding. The amount of events processed depends on |
1134 |
the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>. |
1135 |
|
1136 |
If not all requests were processed for whatever reason, the filehandle |
1137 |
will still be ready when C<poll_cb> returns. |
1138 |
|
1139 |
Example: Install an Event watcher that automatically calls |
1140 |
IO::AIO::poll_cb with high priority: |
1141 |
|
1142 |
Event->io (fd => IO::AIO::poll_fileno, |
1143 |
poll => 'r', async => 1, |
1144 |
cb => \&IO::AIO::poll_cb); |
1145 |
|
1146 |
=item IO::AIO::max_poll_reqs $nreqs |
1147 |
|
1148 |
=item IO::AIO::max_poll_time $seconds |
1149 |
|
1150 |
These set the maximum number of requests (default C<0>, meaning infinity) |
1151 |
that are being processed by C<IO::AIO::poll_cb> in one call, respectively |
1152 |
the maximum amount of time (default C<0>, meaning infinity) spent in |
1153 |
C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount |
1154 |
of time C<poll_cb> is allowed to use). |
1155 |
|
1156 |
Setting C<max_poll_time> to a non-zero value creates an overhead of one |
1157 |
syscall per request processed, which is not normally a problem unless your |
1158 |
callbacks are really really fast or your OS is really really slow (I am |
1159 |
not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead. |
1160 |
|
1161 |
Setting these is useful if you want to ensure some level of |
1162 |
interactiveness when perl is not fast enough to process all requests in |
1163 |
time. |
1164 |
|
1165 |
For interactive programs, values such as C<0.01> to C<0.1> should be fine. |
1166 |
|
1167 |
Example: Install an Event watcher that automatically calls |
1168 |
IO::AIO::poll_cb with low priority, to ensure that other parts of the |
1169 |
program get the CPU sometimes even under high AIO load. |
1170 |
|
1171 |
# try not to spend much more than 0.1s in poll_cb |
1172 |
IO::AIO::max_poll_time 0.1; |
1173 |
|
1174 |
# use a low priority so other tasks have priority |
1175 |
Event->io (fd => IO::AIO::poll_fileno, |
1176 |
poll => 'r', nice => 1, |
1177 |
cb => &IO::AIO::poll_cb); |
1178 |
|
1179 |
=item IO::AIO::poll_wait |
1180 |
|
1181 |
If there are any outstanding requests and none of them in the result |
1182 |
phase, wait till the result filehandle becomes ready for reading (simply |
1183 |
does a C<select> on the filehandle. This is useful if you want to |
1184 |
synchronously wait for some requests to finish). |
1185 |
|
1186 |
See C<nreqs> for an example. |
1187 |
|
1188 |
=item IO::AIO::poll |
1189 |
|
1190 |
Waits until some requests have been handled. |
1191 |
|
1192 |
Returns the number of requests processed, but is otherwise strictly |
1193 |
equivalent to: |
1194 |
|
1195 |
IO::AIO::poll_wait, IO::AIO::poll_cb |
1196 |
|
1197 |
=item IO::AIO::flush |
1198 |
|
1199 |
Wait till all outstanding AIO requests have been handled. |
1200 |
|
1201 |
Strictly equivalent to: |
1202 |
|
1203 |
IO::AIO::poll_wait, IO::AIO::poll_cb |
1204 |
while IO::AIO::nreqs; |
1205 |
|
1206 |
=back |
1207 |
|
1208 |
=head3 CONTROLLING THE NUMBER OF THREADS |
1209 |
|
1210 |
=over |
1211 |
|
1212 |
=item IO::AIO::min_parallel $nthreads |
1213 |
|
1214 |
Set the minimum number of AIO threads to C<$nthreads>. The current |
1215 |
default is C<8>, which means eight asynchronous operations can execute |
1216 |
concurrently at any one time (the number of outstanding requests, |
1217 |
however, is unlimited). |
1218 |
|
1219 |
IO::AIO starts threads only on demand, when an AIO request is queued and |
1220 |
no free thread exists. Please note that queueing up a hundred requests can |
1221 |
create demand for a hundred threads, even if it turns out that everything |
1222 |
is in the cache and could have been processed faster by a single thread. |
1223 |
|
1224 |
It is recommended to keep the number of threads relatively low, as some |
1225 |
Linux kernel versions will scale negatively with the number of threads |
1226 |
(higher parallelity => MUCH higher latency). With current Linux 2.6 |
1227 |
versions, 4-32 threads should be fine. |
1228 |
|
1229 |
Under most circumstances you don't need to call this function, as the |
1230 |
module selects a default that is suitable for low to moderate load. |
1231 |
|
1232 |
=item IO::AIO::max_parallel $nthreads |
1233 |
|
1234 |
Sets the maximum number of AIO threads to C<$nthreads>. If more than the |
1235 |
specified number of threads are currently running, this function kills |
1236 |
them. This function blocks until the limit is reached. |
1237 |
|
1238 |
While C<$nthreads> are zero, aio requests get queued but not executed |
1239 |
until the number of threads has been increased again. |
1240 |
|
1241 |
This module automatically runs C<max_parallel 0> at program end, to ensure |
1242 |
that all threads are killed and that there are no outstanding requests. |
1243 |
|
1244 |
Under normal circumstances you don't need to call this function. |
1245 |
|
1246 |
=item IO::AIO::max_idle $nthreads |
1247 |
|
1248 |
Limit the number of threads (default: 4) that are allowed to idle (i.e., |
1249 |
threads that did not get a request to process within 10 seconds). That |
1250 |
means if a thread becomes idle while C<$nthreads> other threads are also |
1251 |
idle, it will free its resources and exit. |
1252 |
|
1253 |
This is useful when you allow a large number of threads (e.g. 100 or 1000) |
1254 |
to allow for extremely high load situations, but want to free resources |
1255 |
under normal circumstances (1000 threads can easily consume 30MB of RAM). |
1256 |
|
1257 |
The default is probably ok in most situations, especially if thread |
1258 |
creation is fast. If thread creation is very slow on your system you might |
1259 |
want to use larger values. |
1260 |
|
1261 |
=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs |
1262 |
|
1263 |
This is a very bad function to use in interactive programs because it |
1264 |
blocks, and a bad way to reduce concurrency because it is inexact: Better |
1265 |
use an C<aio_group> together with a feed callback. |
1266 |
|
1267 |
Sets the maximum number of outstanding requests to C<$nreqs>. If you |
1268 |
do queue up more than this number of requests, the next call to the |
1269 |
C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>) |
1270 |
function will block until the limit is no longer exceeded. |
1271 |
|
1272 |
The default value is very large, so there is no practical limit on the |
1273 |
number of outstanding requests. |
1274 |
|
1275 |
You can still queue as many requests as you want. Therefore, |
1276 |
C<max_oustsanding> is mainly useful in simple scripts (with low values) or |
1277 |
as a stop gap to shield against fatal memory overflow (with large values). |
1278 |
|
1279 |
=back |
1280 |
|
1281 |
=head3 STATISTICAL INFORMATION |
1282 |
|
1283 |
=over |
1284 |
|
1285 |
=item IO::AIO::nreqs |
1286 |
|
1287 |
Returns the number of requests currently in the ready, execute or pending |
1288 |
states (i.e. for which their callback has not been invoked yet). |
1289 |
|
1290 |
Example: wait till there are no outstanding requests anymore: |
1291 |
|
1292 |
IO::AIO::poll_wait, IO::AIO::poll_cb |
1293 |
while IO::AIO::nreqs; |
1294 |
|
1295 |
=item IO::AIO::nready |
1296 |
|
1297 |
Returns the number of requests currently in the ready state (not yet |
1298 |
executed). |
1299 |
|
1300 |
=item IO::AIO::npending |
1301 |
|
1302 |
Returns the number of requests currently in the pending state (executed, |
1303 |
but not yet processed by poll_cb). |
1304 |
|
1305 |
=back |
1306 |
|
1307 |
=cut |
1308 |
|
1309 |
min_parallel 8; |
1310 |
|
1311 |
END { flush } |
1312 |
|
1313 |
1; |
1314 |
|
1315 |
=head2 FORK BEHAVIOUR |
1316 |
|
1317 |
This module should do "the right thing" when the process using it forks: |
1318 |
|
1319 |
Before the fork, IO::AIO enters a quiescent state where no requests |
1320 |
can be added in other threads and no results will be processed. After |
1321 |
the fork the parent simply leaves the quiescent state and continues |
1322 |
request/result processing, while the child frees the request/result queue |
1323 |
(so that the requests started before the fork will only be handled in the |
1324 |
parent). Threads will be started on demand until the limit set in the |
1325 |
parent process has been reached again. |
1326 |
|
1327 |
In short: the parent will, after a short pause, continue as if fork had |
1328 |
not been called, while the child will act as if IO::AIO has not been used |
1329 |
yet. |
1330 |
|
1331 |
=head2 MEMORY USAGE |
1332 |
|
1333 |
Per-request usage: |
1334 |
|
1335 |
Each aio request uses - depending on your architecture - around 100-200 |
1336 |
bytes of memory. In addition, stat requests need a stat buffer (possibly |
1337 |
a few hundred bytes), readdir requires a result buffer and so on. Perl |
1338 |
scalars and other data passed into aio requests will also be locked and |
1339 |
will consume memory till the request has entered the done state. |
1340 |
|
1341 |
This is not awfully much, so queuing lots of requests is not usually a |
1342 |
problem. |
1343 |
|
1344 |
Per-thread usage: |
1345 |
|
1346 |
In the execution phase, some aio requests require more memory for |
1347 |
temporary buffers, and each thread requires a stack and other data |
1348 |
structures (usually around 16k-128k, depending on the OS). |
1349 |
|
1350 |
=head1 KNOWN BUGS |
1351 |
|
1352 |
Known bugs will be fixed in the next release. |
1353 |
|
1354 |
=head1 SEE ALSO |
1355 |
|
1356 |
L<Coro::AIO>. |
1357 |
|
1358 |
=head1 AUTHOR |
1359 |
|
1360 |
Marc Lehmann <schmorp@schmorp.de> |
1361 |
http://home.schmorp.de/ |
1362 |
|
1363 |
=cut |
1364 |
|