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Revision 1.53 by root, Sat Oct 21 23:20:29 2006 UTC vs.
Revision 1.107 by root, Fri Jun 1 05:52:59 2007 UTC

5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 use IO::AIO; 7 use IO::AIO;
8 8
9 aio_open "/etc/passwd", O_RDONLY, 0, sub { 9 aio_open "/etc/passwd", O_RDONLY, 0, sub {
10 my ($fh) = @_; 10 my $fh = shift
11 or die "/etc/passwd: $!";
11 ... 12 ...
12 }; 13 };
13 14
14 aio_unlink "/tmp/file", sub { }; 15 aio_unlink "/tmp/file", sub { };
15 16
16 aio_read $fh, 30000, 1024, $buffer, 0, sub { 17 aio_read $fh, 30000, 1024, $buffer, 0, sub {
17 $_[0] > 0 or die "read error: $!"; 18 $_[0] > 0 or die "read error: $!";
18 }; 19 };
19 20
20 use IO::AIO 2; # version has aio objects 21 # version 2+ has request and group objects
22 use IO::AIO 2;
21 23
24 aioreq_pri 4; # give next request a very high priority
22 my $req = aio_unlink "/tmp/file", sub { }; 25 my $req = aio_unlink "/tmp/file", sub { };
23 $req->cancel; # cancel request if still in queue 26 $req->cancel; # cancel request if still in queue
24 27
25 # AnyEvent 28 my $grp = aio_group sub { print "all stats done\n" };
29 add $grp aio_stat "..." for ...;
30
31 # AnyEvent integration
26 open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!"; 32 open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
27 my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb }); 33 my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
28 34
29 # Event 35 # Event integration
30 Event->io (fd => IO::AIO::poll_fileno, 36 Event->io (fd => IO::AIO::poll_fileno,
31 poll => 'r', 37 poll => 'r',
32 cb => \&IO::AIO::poll_cb); 38 cb => \&IO::AIO::poll_cb);
33 39
34 # Glib/Gtk2 40 # Glib/Gtk2 integration
35 add_watch Glib::IO IO::AIO::poll_fileno, 41 add_watch Glib::IO IO::AIO::poll_fileno,
36 in => sub { IO::AIO::poll_cb; 1 }; 42 in => sub { IO::AIO::poll_cb; 1 };
37 43
38 # Tk 44 # Tk integration
39 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "", 45 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
40 readable => \&IO::AIO::poll_cb); 46 readable => \&IO::AIO::poll_cb);
41 47
42 # Danga::Socket 48 # Danga::Socket integration
43 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno => 49 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
44 \&IO::AIO::poll_cb); 50 \&IO::AIO::poll_cb);
45 51
46
47=head1 DESCRIPTION 52=head1 DESCRIPTION
48 53
49This module implements asynchronous I/O using whatever means your 54This module implements asynchronous I/O using whatever means your
50operating system supports. 55operating system supports.
51 56
57Asynchronous means that operations that can normally block your program
58(e.g. reading from disk) will be done asynchronously: the operation
59will still block, but you can do something else in the meantime. This
60is extremely useful for programs that need to stay interactive even
61when doing heavy I/O (GUI programs, high performance network servers
62etc.), but can also be used to easily do operations in parallel that are
63normally done sequentially, e.g. stat'ing many files, which is much faster
64on a RAID volume or over NFS when you do a number of stat operations
65concurrently.
66
67While most of this works on all types of file descriptors (for example
68sockets), using these functions on file descriptors that support
69nonblocking operation (again, sockets, pipes etc.) is very inefficient or
70might not work (aio_read fails on sockets/pipes/fifos). Use an event loop
71for that (such as the L<Event|Event> module): IO::AIO will naturally fit
72into such an event loop itself.
73
52Currently, a number of threads are started that execute your read/writes 74In this version, a number of threads are started that execute your
53and signal their completion. You don't need thread support in your libc or 75requests and signal their completion. You don't need thread support
54perl, and the threads created by this module will not be visible to the 76in perl, and the threads created by this module will not be visible
55pthreads library. In the future, this module might make use of the native 77to perl. In the future, this module might make use of the native aio
56aio functions available on many operating systems. However, they are often 78functions available on many operating systems. However, they are often
57not well-supported (Linux doesn't allow them on normal files currently, 79not well-supported or restricted (GNU/Linux doesn't allow them on normal
58for example), and they would only support aio_read and aio_write, so the 80files currently, for example), and they would only support aio_read and
59remaining functionality would have to be implemented using threads anyway. 81aio_write, so the remaining functionality would have to be implemented
82using threads anyway.
60 83
61Although the module will work with in the presence of other threads, it is 84Although the module will work with in the presence of other (Perl-)
62currently not reentrant, so use appropriate locking yourself, always call 85threads, it is currently not reentrant in any way, so use appropriate
63C<poll_cb> from within the same thread, or never call C<poll_cb> (or other 86locking yourself, always call C<poll_cb> from within the same thread, or
64C<aio_> functions) recursively. 87never call C<poll_cb> (or other C<aio_> functions) recursively.
88
89=head2 EXAMPLE
90
91This is a simple example that uses the Event module and loads
92F</etc/passwd> asynchronously:
93
94 use Fcntl;
95 use Event;
96 use IO::AIO;
97
98 # register the IO::AIO callback with Event
99 Event->io (fd => IO::AIO::poll_fileno,
100 poll => 'r',
101 cb => \&IO::AIO::poll_cb);
102
103 # queue the request to open /etc/passwd
104 aio_open "/etc/passwd", O_RDONLY, 0, sub {
105 my $fh = shift
106 or die "error while opening: $!";
107
108 # stat'ing filehandles is generally non-blocking
109 my $size = -s $fh;
110
111 # queue a request to read the file
112 my $contents;
113 aio_read $fh, 0, $size, $contents, 0, sub {
114 $_[0] == $size
115 or die "short read: $!";
116
117 close $fh;
118
119 # file contents now in $contents
120 print $contents;
121
122 # exit event loop and program
123 Event::unloop;
124 };
125 };
126
127 # possibly queue up other requests, or open GUI windows,
128 # check for sockets etc. etc.
129
130 # process events as long as there are some:
131 Event::loop;
132
133=head1 REQUEST ANATOMY AND LIFETIME
134
135Every C<aio_*> function creates a request. which is a C data structure not
136directly visible to Perl.
137
138If called in non-void context, every request function returns a Perl
139object representing the request. In void context, nothing is returned,
140which saves a bit of memory.
141
142The perl object is a fairly standard ref-to-hash object. The hash contents
143are not used by IO::AIO so you are free to store anything you like in it.
144
145During their existance, aio requests travel through the following states,
146in order:
147
148=over 4
149
150=item ready
151
152Immediately after a request is created it is put into the ready state,
153waiting for a thread to execute it.
154
155=item execute
156
157A thread has accepted the request for processing and is currently
158executing it (e.g. blocking in read).
159
160=item pending
161
162The request has been executed and is waiting for result processing.
163
164While request submission and execution is fully asynchronous, result
165processing is not and relies on the perl interpreter calling C<poll_cb>
166(or another function with the same effect).
167
168=item result
169
170The request results are processed synchronously by C<poll_cb>.
171
172The C<poll_cb> function will process all outstanding aio requests by
173calling their callbacks, freeing memory associated with them and managing
174any groups they are contained in.
175
176=item done
177
178Request has reached the end of its lifetime and holds no resources anymore
179(except possibly for the Perl object, but its connection to the actual
180aio request is severed and calling its methods will either do nothing or
181result in a runtime error).
182
183=back
65 184
66=cut 185=cut
67 186
68package IO::AIO; 187package IO::AIO;
69 188
71use strict 'vars'; 190use strict 'vars';
72 191
73use base 'Exporter'; 192use base 'Exporter';
74 193
75BEGIN { 194BEGIN {
76 our $VERSION = '1.99'; 195 our $VERSION = '2.4';
77 196
78 our @EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat 197 our @AIO_REQ = 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 198 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); 199 aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link
81 our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs); 200 aio_move aio_copy aio_group aio_nop aio_mknod aio_load aio_rmtree aio_mkdir
201 aio_chown aio_chmod aio_utime);
202 our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice aio_block));
203 our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
204 min_parallel max_parallel max_idle
205 nreqs nready npending nthreads
206 max_poll_time max_poll_reqs);
207
208 @IO::AIO::GRP::ISA = 'IO::AIO::REQ';
82 209
83 require XSLoader; 210 require XSLoader;
84 XSLoader::load ("IO::AIO", $VERSION); 211 XSLoader::load ("IO::AIO", $VERSION);
85} 212}
86 213
87=head1 FUNCTIONS 214=head1 FUNCTIONS
88 215
89=head2 AIO FUNCTIONS 216=head2 AIO REQUEST FUNCTIONS
90 217
91All the C<aio_*> calls are more or less thin wrappers around the syscall 218All the C<aio_*> calls are more or less thin wrappers around the syscall
92with the same name (sans C<aio_>). The arguments are similar or identical, 219with the same name (sans C<aio_>). The arguments are similar or identical,
93and they all accept an additional (and optional) C<$callback> argument 220and they all accept an additional (and optional) C<$callback> argument
94which must be a code reference. This code reference will get called with 221which must be a code reference. This code reference will get called with
97syscall has been executed asynchronously. 224syscall has been executed asynchronously.
98 225
99All functions expecting a filehandle keep a copy of the filehandle 226All functions expecting a filehandle keep a copy of the filehandle
100internally until the request has finished. 227internally until the request has finished.
101 228
102All non-composite requests (requests that are not broken down into
103multiple requests) return objects of type L<IO::AIO::REQ> that allow 229All functions return request objects of type L<IO::AIO::REQ> that allow
104further manipulation of running requests. 230further manipulation of those requests while they are in-flight.
105 231
106The pathnames you pass to these routines I<must> be absolute and 232The pathnames you pass to these routines I<must> be absolute and
107encoded in byte form. The reason for the former is that at the time the 233encoded as octets. The reason for the former is that at the time the
108request is being executed, the current working directory could have 234request is being executed, the current working directory could have
109changed. Alternatively, you can make sure that you never change the 235changed. Alternatively, you can make sure that you never change the
110current working directory. 236current working directory anywhere in the program and then use relative
237paths.
111 238
112To encode pathnames to byte form, either make sure you either: a) 239To encode pathnames as octets, either make sure you either: a) always pass
113always pass in filenames you got from outside (command line, readdir 240in filenames you got from outside (command line, readdir etc.) without
114etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode 241tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
115your pathnames to the locale (or other) encoding in effect in the user 242your pathnames to the locale (or other) encoding in effect in the user
116environment, d) use Glib::filename_from_unicode on unicode filenames or e) 243environment, d) use Glib::filename_from_unicode on unicode filenames or e)
117use something else. 244use something else to ensure your scalar has the correct contents.
245
246This works, btw. independent of the internal UTF-8 bit, which IO::AIO
247handles correctly wether it is set or not.
118 248
119=over 4 249=over 4
250
251=item $prev_pri = aioreq_pri [$pri]
252
253Returns the priority value that would be used for the next request and, if
254C<$pri> is given, sets the priority for the next aio request.
255
256The default priority is C<0>, the minimum and maximum priorities are C<-4>
257and C<4>, respectively. Requests with higher priority will be serviced
258first.
259
260The priority will be reset to C<0> after each call to one of the C<aio_*>
261functions.
262
263Example: open a file with low priority, then read something from it with
264higher priority so the read request is serviced before other low priority
265open requests (potentially spamming the cache):
266
267 aioreq_pri -3;
268 aio_open ..., sub {
269 return unless $_[0];
270
271 aioreq_pri -2;
272 aio_read $_[0], ..., sub {
273 ...
274 };
275 };
276
277
278=item aioreq_nice $pri_adjust
279
280Similar to C<aioreq_pri>, but subtracts the given value from the current
281priority, so the effect is cumulative.
282
120 283
121=item aio_open $pathname, $flags, $mode, $callback->($fh) 284=item aio_open $pathname, $flags, $mode, $callback->($fh)
122 285
123Asynchronously open or create a file and call the callback with a newly 286Asynchronously open or create a file and call the callback with a newly
124created filehandle for the file. 287created filehandle for the file.
130list. They are the same as used by C<sysopen>. 293list. They are the same as used by C<sysopen>.
131 294
132Likewise, C<$mode> specifies the mode of the newly created file, if it 295Likewise, C<$mode> specifies the mode of the newly created file, if it
133didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>, 296didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
134except that it is mandatory (i.e. use C<0> if you don't create new files, 297except that it is mandatory (i.e. use C<0> if you don't create new files,
135and C<0666> or C<0777> if you do). 298and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
299by the umask in effect then the request is being executed, so better never
300change the umask.
136 301
137Example: 302Example:
138 303
139 aio_open "/etc/passwd", O_RDONLY, 0, sub { 304 aio_open "/etc/passwd", O_RDONLY, 0, sub {
140 if ($_[0]) { 305 if ($_[0]) {
143 } else { 308 } else {
144 die "open failed: $!\n"; 309 die "open failed: $!\n";
145 } 310 }
146 }; 311 };
147 312
313
148=item aio_close $fh, $callback->($status) 314=item aio_close $fh, $callback->($status)
149 315
150Asynchronously close a file and call the callback with the result 316Asynchronously close a file and call the callback with the result
151code. I<WARNING:> although accepted, you should not pass in a perl 317code. I<WARNING:> although accepted, you should not pass in a perl
152filehandle here, as perl will likely close the file descriptor another 318filehandle here, as perl will likely close the file descriptor another
154C<close> or just let filehandles go out of scope. 320C<close> or just let filehandles go out of scope.
155 321
156This is supposed to be a bug in the API, so that might change. It's 322This is supposed to be a bug in the API, so that might change. It's
157therefore best to avoid this function. 323therefore best to avoid this function.
158 324
325
159=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 326=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
160 327
161=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 328=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
162 329
163Reads or writes C<length> bytes from the specified C<fh> and C<offset> 330Reads or writes C<length> bytes from the specified C<fh> and C<offset>
175 aio_read $fh, 7, 15, $buffer, 0, sub { 342 aio_read $fh, 7, 15, $buffer, 0, sub {
176 $_[0] > 0 or die "read error: $!"; 343 $_[0] > 0 or die "read error: $!";
177 print "read $_[0] bytes: <$buffer>\n"; 344 print "read $_[0] bytes: <$buffer>\n";
178 }; 345 };
179 346
180=item aio_move $srcpath, $dstpath, $callback->($status)
181
182Try to move the I<file> (directories not supported as either source or
183destination) from C<$srcpath> to C<$dstpath> and call the callback with
184the C<0> (error) or C<-1> ok.
185
186This is a composite request that tries to rename(2) the file first. If
187rename files with C<EXDEV>, it creates the destination file with mode 0200
188and copies the contents of the source file into it using C<aio_sendfile>,
189followed by restoring atime, mtime, access mode and uid/gid, in that
190order, and unlinking the C<$srcpath>.
191
192If an error occurs, the partial destination file will be unlinked, if
193possible, except when setting atime, mtime, access mode and uid/gid, where
194errors are being ignored.
195
196=cut
197
198sub 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}
243 347
244=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 348=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
245 349
246Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts 350Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
247reading at byte offset C<$in_offset>, and starts writing at the current 351reading at byte offset C<$in_offset>, and starts writing at the current
261C<$in_fh> than are written, and there is no way to find out how many 365C<$in_fh> than are written, and there is no way to find out how many
262bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only 366bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
263provides the number of bytes written to C<$out_fh>. Only if the result 367provides the number of bytes written to C<$out_fh>. Only if the result
264value equals C<$length> one can assume that C<$length> bytes have been 368value equals C<$length> one can assume that C<$length> bytes have been
265read. 369read.
370
266 371
267=item aio_readahead $fh,$offset,$length, $callback->($retval) 372=item aio_readahead $fh,$offset,$length, $callback->($retval)
268 373
269C<aio_readahead> populates the page cache with data from a file so that 374C<aio_readahead> populates the page cache with data from a file so that
270subsequent reads from that file will not block on disk I/O. The C<$offset> 375subsequent reads from that file will not block on disk I/O. The C<$offset>
276file. The current file offset of the file is left unchanged. 381file. The current file offset of the file is left unchanged.
277 382
278If that syscall doesn't exist (likely if your OS isn't Linux) it will be 383If that syscall doesn't exist (likely if your OS isn't Linux) it will be
279emulated by simply reading the data, which would have a similar effect. 384emulated by simply reading the data, which would have a similar effect.
280 385
386
281=item aio_stat $fh_or_path, $callback->($status) 387=item aio_stat $fh_or_path, $callback->($status)
282 388
283=item aio_lstat $fh, $callback->($status) 389=item aio_lstat $fh, $callback->($status)
284 390
285Works like perl's C<stat> or C<lstat> in void context. The callback will 391Works like perl's C<stat> or C<lstat> in void context. The callback will
298 aio_stat "/etc/passwd", sub { 404 aio_stat "/etc/passwd", sub {
299 $_[0] and die "stat failed: $!"; 405 $_[0] and die "stat failed: $!";
300 print "size is ", -s _, "\n"; 406 print "size is ", -s _, "\n";
301 }; 407 };
302 408
409
410=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
411
412Works like perl's C<utime> function (including the special case of $atime
413and $mtime being undef). Fractional times are supported if the underlying
414syscalls support them.
415
416When called with a pathname, uses utimes(2) if available, otherwise
417utime(2). If called on a file descriptor, uses futimes(2) if available,
418otherwise returns ENOSYS, so this is not portable.
419
420Examples:
421
422 # set atime and mtime to current time (basically touch(1)):
423 aio_utime "path", undef, undef;
424 # set atime to current time and mtime to beginning of the epoch:
425 aio_utime "path", time, undef; # undef==0
426
427
428=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
429
430Works like perl's C<chown> function, except that C<undef> for either $uid
431or $gid is being interpreted as "do not change" (but -1 can also be used).
432
433Examples:
434
435 # same as "chown root path" in the shell:
436 aio_chown "path", 0, -1;
437 # same as above:
438 aio_chown "path", 0, undef;
439
440
441=item aio_chmod $fh_or_path, $mode, $callback->($status)
442
443Works like perl's C<chmod> function.
444
445
303=item aio_unlink $pathname, $callback->($status) 446=item aio_unlink $pathname, $callback->($status)
304 447
305Asynchronously unlink (delete) a file and call the callback with the 448Asynchronously unlink (delete) a file and call the callback with the
306result code. 449result code.
307 450
451
452=item aio_mknod $path, $mode, $dev, $callback->($status)
453
454[EXPERIMENTAL]
455
456Asynchronously create a device node (or fifo). See mknod(2).
457
458The only (POSIX-) portable way of calling this function is:
459
460 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
461
462
308=item aio_link $srcpath, $dstpath, $callback->($status) 463=item aio_link $srcpath, $dstpath, $callback->($status)
309 464
310Asynchronously create a new link to the existing object at C<$srcpath> at 465Asynchronously create a new link to the existing object at C<$srcpath> at
311the path C<$dstpath> and call the callback with the result code. 466the path C<$dstpath> and call the callback with the result code.
312 467
468
313=item aio_symlink $srcpath, $dstpath, $callback->($status) 469=item aio_symlink $srcpath, $dstpath, $callback->($status)
314 470
315Asynchronously create a new symbolic link to the existing object at C<$srcpath> at 471Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
316the path C<$dstpath> and call the callback with the result code. 472the path C<$dstpath> and call the callback with the result code.
317 473
474
475=item aio_readlink $path, $callback->($link)
476
477Asynchronously read the symlink specified by C<$path> and pass it to
478the callback. If an error occurs, nothing or undef gets passed to the
479callback.
480
481
318=item aio_rename $srcpath, $dstpath, $callback->($status) 482=item aio_rename $srcpath, $dstpath, $callback->($status)
319 483
320Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as 484Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
321rename(2) and call the callback with the result code. 485rename(2) and call the callback with the result code.
322 486
487
488=item aio_mkdir $pathname, $mode, $callback->($status)
489
490Asynchronously mkdir (create) a directory and call the callback with
491the result code. C<$mode> will be modified by the umask at the time the
492request is executed, so do not change your umask.
493
494
323=item aio_rmdir $pathname, $callback->($status) 495=item aio_rmdir $pathname, $callback->($status)
324 496
325Asynchronously rmdir (delete) a directory and call the callback with the 497Asynchronously rmdir (delete) a directory and call the callback with the
326result code. 498result code.
499
327 500
328=item aio_readdir $pathname, $callback->($entries) 501=item aio_readdir $pathname, $callback->($entries)
329 502
330Unlike the POSIX call of the same name, C<aio_readdir> reads an entire 503Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
331directory (i.e. opendir + readdir + closedir). The entries will not be 504directory (i.e. opendir + readdir + closedir). The entries will not be
332sorted, and will B<NOT> include the C<.> and C<..> entries. 505sorted, and will B<NOT> include the C<.> and C<..> entries.
333 506
334The callback a single argument which is either C<undef> or an array-ref 507The callback a single argument which is either C<undef> or an array-ref
335with the filenames. 508with the filenames.
336 509
510
511=item aio_load $path, $data, $callback->($status)
512
513This is a composite request that tries to fully load the given file into
514memory. Status is the same as with aio_read.
515
516=cut
517
518sub aio_load($$;$) {
519 aio_block {
520 my ($path, undef, $cb) = @_;
521 my $data = \$_[1];
522
523 my $pri = aioreq_pri;
524 my $grp = aio_group $cb;
525
526 aioreq_pri $pri;
527 add $grp aio_open $path, O_RDONLY, 0, sub {
528 my $fh = shift
529 or return $grp->result (-1);
530
531 aioreq_pri $pri;
532 add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
533 $grp->result ($_[0]);
534 };
535 };
536
537 $grp
538 }
539}
540
541=item aio_copy $srcpath, $dstpath, $callback->($status)
542
543Try to copy the I<file> (directories not supported as either source or
544destination) from C<$srcpath> to C<$dstpath> and call the callback with
545the C<0> (error) or C<-1> ok.
546
547This is a composite request that it creates the destination file with
548mode 0200 and copies the contents of the source file into it using
549C<aio_sendfile>, followed by restoring atime, mtime, access mode and
550uid/gid, in that order.
551
552If an error occurs, the partial destination file will be unlinked, if
553possible, except when setting atime, mtime, access mode and uid/gid, where
554errors are being ignored.
555
556=cut
557
558sub aio_copy($$;$) {
559 aio_block {
560 my ($src, $dst, $cb) = @_;
561
562 my $pri = aioreq_pri;
563 my $grp = aio_group $cb;
564
565 aioreq_pri $pri;
566 add $grp aio_open $src, O_RDONLY, 0, sub {
567 if (my $src_fh = $_[0]) {
568 my @stat = stat $src_fh;
569
570 aioreq_pri $pri;
571 add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
572 if (my $dst_fh = $_[0]) {
573 aioreq_pri $pri;
574 add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
575 if ($_[0] == $stat[7]) {
576 $grp->result (0);
577 close $src_fh;
578
579 # those should not normally block. should. should.
580 utime $stat[8], $stat[9], $dst;
581 chmod $stat[2] & 07777, $dst_fh;
582 chown $stat[4], $stat[5], $dst_fh;
583 close $dst_fh;
584 } else {
585 $grp->result (-1);
586 close $src_fh;
587 close $dst_fh;
588
589 aioreq $pri;
590 add $grp aio_unlink $dst;
591 }
592 };
593 } else {
594 $grp->result (-1);
595 }
596 },
597
598 } else {
599 $grp->result (-1);
600 }
601 };
602
603 $grp
604 }
605}
606
607=item aio_move $srcpath, $dstpath, $callback->($status)
608
609Try to move the I<file> (directories not supported as either source or
610destination) from C<$srcpath> to C<$dstpath> and call the callback with
611the C<0> (error) or C<-1> ok.
612
613This is a composite request that tries to rename(2) the file first. If
614rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
615that is successful, unlinking the C<$srcpath>.
616
617=cut
618
619sub aio_move($$;$) {
620 aio_block {
621 my ($src, $dst, $cb) = @_;
622
623 my $pri = aioreq_pri;
624 my $grp = aio_group $cb;
625
626 aioreq_pri $pri;
627 add $grp aio_rename $src, $dst, sub {
628 if ($_[0] && $! == EXDEV) {
629 aioreq_pri $pri;
630 add $grp aio_copy $src, $dst, sub {
631 $grp->result ($_[0]);
632
633 if (!$_[0]) {
634 aioreq_pri $pri;
635 add $grp aio_unlink $src;
636 }
637 };
638 } else {
639 $grp->result ($_[0]);
640 }
641 };
642
643 $grp
644 }
645}
646
337=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 647=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
338 648
339Scans a directory (similar to C<aio_readdir>) but additionally tries to 649Scans a directory (similar to C<aio_readdir>) but additionally tries to
340separate the entries of directory C<$path> into two sets of names, ones 650efficiently separate the entries of directory C<$path> into two sets of
341you can recurse into (directories or links to them), and ones you cannot 651names, directories you can recurse into (directories), and ones you cannot
342recurse into (everything else). 652recurse into (everything else, including symlinks to directories).
343 653
344C<aio_scandir> is a composite request that consists of many sub 654C<aio_scandir> is a composite request that creates of many sub requests_
345requests. C<$maxreq> specifies the maximum number of outstanding aio 655C<$maxreq> specifies the maximum number of outstanding aio requests that
346requests that this function generates. If it is C<< <= 0 >>, then a 656this function generates. If it is C<< <= 0 >>, then a suitable default
347suitable default will be chosen (currently 8). 657will be chosen (currently 4).
348 658
349On error, the callback is called without arguments, otherwise it receives 659On error, the callback is called without arguments, otherwise it receives
350two array-refs with path-relative entry names. 660two array-refs with path-relative entry names.
351 661
352Example: 662Example:
386as those tend to return 0 or 1 as link counts, which disables the 696as those tend to return 0 or 1 as link counts, which disables the
387directory counting heuristic. 697directory counting heuristic.
388 698
389=cut 699=cut
390 700
391sub aio_scandir($$$) { 701sub aio_scandir($$;$) {
702 aio_block {
392 my ($path, $maxreq, $cb) = @_; 703 my ($path, $maxreq, $cb) = @_;
393 704
705 my $pri = aioreq_pri;
706
707 my $grp = aio_group $cb;
708
394 $maxreq = 8 if $maxreq <= 0; 709 $maxreq = 4 if $maxreq <= 0;
395 710
396 # stat once 711 # stat once
712 aioreq_pri $pri;
397 aio_stat $path, sub { 713 add $grp aio_stat $path, sub {
398 return $cb->() if $_[0]; 714 return $grp->result () if $_[0];
399 my $now = time; 715 my $now = time;
400 my $hash1 = join ":", (stat _)[0,1,3,7,9]; 716 my $hash1 = join ":", (stat _)[0,1,3,7,9];
401 717
402 # read the directory entries 718 # read the directory entries
719 aioreq_pri $pri;
403 aio_readdir $path, sub { 720 add $grp aio_readdir $path, sub {
404 my $entries = shift 721 my $entries = shift
405 or return $cb->(); 722 or return $grp->result ();
406 723
407 # stat the dir another time 724 # stat the dir another time
725 aioreq_pri $pri;
408 aio_stat $path, sub { 726 add $grp aio_stat $path, sub {
409 my $hash2 = join ":", (stat _)[0,1,3,7,9]; 727 my $hash2 = join ":", (stat _)[0,1,3,7,9];
410 728
411 my $ndirs; 729 my $ndirs;
412 730
413 # take the slow route if anything looks fishy 731 # take the slow route if anything looks fishy
414 if ($hash1 ne $hash2 or (stat _)[9] == $now) { 732 if ($hash1 ne $hash2 or (stat _)[9] == $now) {
415 $ndirs = -1; 733 $ndirs = -1;
416 } else { 734 } else {
417 # if nlink == 2, we are finished 735 # if nlink == 2, we are finished
418 # on non-posix-fs's, we rely on nlink < 2 736 # on non-posix-fs's, we rely on nlink < 2
419 $ndirs = (stat _)[3] - 2 737 $ndirs = (stat _)[3] - 2
420 or return $cb->([], $entries); 738 or return $grp->result ([], $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 } 739 }
740
741 # sort into likely dirs and likely nondirs
742 # dirs == files without ".", short entries first
743 $entries = [map $_->[0],
744 sort { $b->[1] cmp $a->[1] }
745 map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
746 @$entries];
747
748 my (@dirs, @nondirs);
749
750 my $statgrp = add $grp aio_group sub {
751 $grp->result (\@dirs, \@nondirs);
752 };
753
754 limit $statgrp $maxreq;
755 feed $statgrp sub {
756 return unless @$entries;
757 my $entry = pop @$entries;
758
759 aioreq_pri $pri;
760 add $statgrp aio_stat "$path/$entry/.", sub {
761 if ($_[0] < 0) {
762 push @nondirs, $entry;
763 } else {
764 # need to check for real directory
765 aioreq_pri $pri;
766 add $statgrp aio_lstat "$path/$entry", sub {
767 if (-d _) {
768 push @dirs, $entry;
769
770 unless (--$ndirs) {
771 push @nondirs, @$entries;
772 feed $statgrp;
773 }
774 } else {
775 push @nondirs, $entry;
776 }
777 }
778 }
779 };
780 };
449 }; 781 };
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 }; 782 };
480 }; 783 };
784
785 $grp
481 }; 786 }
787}
788
789=item aio_rmtree $path, $callback->($status)
790
791Delete a directory tree starting (and including) C<$path>, return the
792status of the final C<rmdir> only. This is a composite request that
793uses C<aio_scandir> to recurse into and rmdir directories, and unlink
794everything else.
795
796=cut
797
798sub aio_rmtree;
799sub aio_rmtree($;$) {
800 aio_block {
801 my ($path, $cb) = @_;
802
803 my $pri = aioreq_pri;
804 my $grp = aio_group $cb;
805
806 aioreq_pri $pri;
807 add $grp aio_scandir $path, 0, sub {
808 my ($dirs, $nondirs) = @_;
809
810 my $dirgrp = aio_group sub {
811 add $grp aio_rmdir $path, sub {
812 $grp->result ($_[0]);
813 };
814 };
815
816 (aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
817 (aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
818
819 add $grp $dirgrp;
820 };
821
822 $grp
823 }
482} 824}
483 825
484=item aio_fsync $fh, $callback->($status) 826=item aio_fsync $fh, $callback->($status)
485 827
486Asynchronously call fsync on the given filehandle and call the callback 828Asynchronously call fsync on the given filehandle and call the callback
492callback with the fdatasync result code. 834callback with the fdatasync result code.
493 835
494If this call isn't available because your OS lacks it or it couldn't be 836If this call isn't available because your OS lacks it or it couldn't be
495detected, it will be emulated by calling C<fsync> instead. 837detected, it will be emulated by calling C<fsync> instead.
496 838
839=item aio_group $callback->(...)
840
841This is a very special aio request: Instead of doing something, it is a
842container for other aio requests, which is useful if you want to bundle
843many requests into a single, composite, request with a definite callback
844and the ability to cancel the whole request with its subrequests.
845
846Returns an object of class L<IO::AIO::GRP>. See its documentation below
847for more info.
848
849Example:
850
851 my $grp = aio_group sub {
852 print "all stats done\n";
853 };
854
855 add $grp
856 (aio_stat ...),
857 (aio_stat ...),
858 ...;
859
860=item aio_nop $callback->()
861
862This is a special request - it does nothing in itself and is only used for
863side effects, such as when you want to add a dummy request to a group so
864that finishing the requests in the group depends on executing the given
865code.
866
867While this request does nothing, it still goes through the execution
868phase and still requires a worker thread. Thus, the callback will not
869be executed immediately but only after other requests in the queue have
870entered their execution phase. This can be used to measure request
871latency.
872
873=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
874
875Mainly used for debugging and benchmarking, this aio request puts one of
876the request workers to sleep for the given time.
877
878While it is theoretically handy to have simple I/O scheduling requests
879like sleep and file handle readable/writable, the overhead this creates is
880immense (it blocks a thread for a long time) so do not use this function
881except to put your application under artificial I/O pressure.
882
497=back 883=back
498 884
499=head2 IO::AIO::REQ CLASS 885=head2 IO::AIO::REQ CLASS
500 886
501All non-aggregate C<aio_*> functions return an object of this class when 887All non-aggregate C<aio_*> functions return an object of this class when
502called in non-void context. 888called in non-void context.
503 889
504A request always moves through the following five states in its lifetime,
505in order: B<ready> (request has been created, but has not been executed
506yet), B<execute> (request is currently being executed), B<pending>
507(request has been executed but callback has not been called yet),
508B<result> (results are being processed synchronously, includes calling the
509callback) and B<done> (request has reached the end of its lifetime and
510holds no resources anymore).
511
512=over 4 890=over 4
513 891
514=item $req->cancel 892=item cancel $req
515 893
516Cancels the request, if possible. Has the effect of skipping execution 894Cancels the request, if possible. Has the effect of skipping execution
517when entering the B<execute> state and skipping calling the callback when 895when entering the B<execute> state and skipping calling the callback when
518entering the the B<result> state, but will leave the request otherwise 896entering the the B<result> state, but will leave the request otherwise
519untouched. That means that requests that currently execute will not be 897untouched. That means that requests that currently execute will not be
520stopped and resources held by the request will not be freed prematurely. 898stopped and resources held by the request will not be freed prematurely.
521 899
900=item cb $req $callback->(...)
901
902Replace (or simply set) the callback registered to the request.
903
522=back 904=back
523 905
906=head2 IO::AIO::GRP CLASS
907
908This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
909objects of this class, too.
910
911A IO::AIO::GRP object is a special request that can contain multiple other
912aio requests.
913
914You create one by calling the C<aio_group> constructing function with a
915callback that will be called when all contained requests have entered the
916C<done> state:
917
918 my $grp = aio_group sub {
919 print "all requests are done\n";
920 };
921
922You add requests by calling the C<add> method with one or more
923C<IO::AIO::REQ> objects:
924
925 $grp->add (aio_unlink "...");
926
927 add $grp aio_stat "...", sub {
928 $_[0] or return $grp->result ("error");
929
930 # add another request dynamically, if first succeeded
931 add $grp aio_open "...", sub {
932 $grp->result ("ok");
933 };
934 };
935
936This makes it very easy to create composite requests (see the source of
937C<aio_move> for an application) that work and feel like simple requests.
938
939=over 4
940
941=item * The IO::AIO::GRP objects will be cleaned up during calls to
942C<IO::AIO::poll_cb>, just like any other request.
943
944=item * They can be canceled like any other request. Canceling will cancel not
945only the request itself, but also all requests it contains.
946
947=item * They can also can also be added to other IO::AIO::GRP objects.
948
949=item * You must not add requests to a group from within the group callback (or
950any later time).
951
952=back
953
954Their lifetime, simplified, looks like this: when they are empty, they
955will finish very quickly. If they contain only requests that are in the
956C<done> state, they will also finish. Otherwise they will continue to
957exist.
958
959That means after creating a group you have some time to add requests. And
960in the callbacks of those requests, you can add further requests to the
961group. And only when all those requests have finished will the the group
962itself finish.
963
964=over 4
965
966=item add $grp ...
967
968=item $grp->add (...)
969
970Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
971be added, including other groups, as long as you do not create circular
972dependencies.
973
974Returns all its arguments.
975
976=item $grp->cancel_subs
977
978Cancel all subrequests and clears any feeder, but not the group request
979itself. Useful when you queued a lot of events but got a result early.
980
981=item $grp->result (...)
982
983Set the result value(s) that will be passed to the group callback when all
984subrequests have finished and set thre groups errno to the current value
985of errno (just like calling C<errno> without an error number). By default,
986no argument will be passed and errno is zero.
987
988=item $grp->errno ([$errno])
989
990Sets the group errno value to C<$errno>, or the current value of errno
991when the argument is missing.
992
993Every aio request has an associated errno value that is restored when
994the callback is invoked. This method lets you change this value from its
995default (0).
996
997Calling C<result> will also set errno, so make sure you either set C<$!>
998before the call to C<result>, or call c<errno> after it.
999
1000=item feed $grp $callback->($grp)
1001
1002Sets a feeder/generator on this group: every group can have an attached
1003generator that generates requests if idle. The idea behind this is that,
1004although you could just queue as many requests as you want in a group,
1005this might starve other requests for a potentially long time. For
1006example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
1007requests, delaying any later requests for a long time.
1008
1009To avoid this, and allow incremental generation of requests, you can
1010instead a group and set a feeder on it that generates those requests. The
1011feed callback will be called whenever there are few enough (see C<limit>,
1012below) requests active in the group itself and is expected to queue more
1013requests.
1014
1015The feed callback can queue as many requests as it likes (i.e. C<add> does
1016not impose any limits).
1017
1018If the feed does not queue more requests when called, it will be
1019automatically removed from the group.
1020
1021If the feed limit is C<0>, it will be set to C<2> automatically.
1022
1023Example:
1024
1025 # stat all files in @files, but only ever use four aio requests concurrently:
1026
1027 my $grp = aio_group sub { print "finished\n" };
1028 limit $grp 4;
1029 feed $grp sub {
1030 my $file = pop @files
1031 or return;
1032
1033 add $grp aio_stat $file, sub { ... };
1034 };
1035
1036=item limit $grp $num
1037
1038Sets the feeder limit for the group: The feeder will be called whenever
1039the group contains less than this many requests.
1040
1041Setting the limit to C<0> will pause the feeding process.
1042
1043=back
1044
524=head2 SUPPORT FUNCTIONS 1045=head2 SUPPORT FUNCTIONS
1046
1047=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
525 1048
526=over 4 1049=over 4
527 1050
528=item $fileno = IO::AIO::poll_fileno 1051=item $fileno = IO::AIO::poll_fileno
529 1052
534 1057
535See C<poll_cb> for an example. 1058See C<poll_cb> for an example.
536 1059
537=item IO::AIO::poll_cb 1060=item IO::AIO::poll_cb
538 1061
539Process all outstanding events on the result pipe. You have to call this 1062Process some outstanding events on the result pipe. You have to call this
540regularly. Returns the number of events processed. Returns immediately 1063regularly. Returns the number of events processed. Returns immediately
541when no events are outstanding. 1064when no events are outstanding. The amount of events processed depends on
1065the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
1066
1067If not all requests were processed for whatever reason, the filehandle
1068will still be ready when C<poll_cb> returns.
542 1069
543Example: Install an Event watcher that automatically calls 1070Example: Install an Event watcher that automatically calls
544IO::AIO::poll_cb with high priority: 1071IO::AIO::poll_cb with high priority:
545 1072
546 Event->io (fd => IO::AIO::poll_fileno, 1073 Event->io (fd => IO::AIO::poll_fileno,
547 poll => 'r', async => 1, 1074 poll => 'r', async => 1,
548 cb => \&IO::AIO::poll_cb); 1075 cb => \&IO::AIO::poll_cb);
549 1076
1077=item IO::AIO::max_poll_reqs $nreqs
1078
1079=item IO::AIO::max_poll_time $seconds
1080
1081These set the maximum number of requests (default C<0>, meaning infinity)
1082that are being processed by C<IO::AIO::poll_cb> in one call, respectively
1083the maximum amount of time (default C<0>, meaning infinity) spent in
1084C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
1085of time C<poll_cb> is allowed to use).
1086
1087Setting C<max_poll_time> to a non-zero value creates an overhead of one
1088syscall per request processed, which is not normally a problem unless your
1089callbacks are really really fast or your OS is really really slow (I am
1090not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
1091
1092Setting these is useful if you want to ensure some level of
1093interactiveness when perl is not fast enough to process all requests in
1094time.
1095
1096For interactive programs, values such as C<0.01> to C<0.1> should be fine.
1097
1098Example: Install an Event watcher that automatically calls
1099IO::AIO::poll_cb with low priority, to ensure that other parts of the
1100program get the CPU sometimes even under high AIO load.
1101
1102 # try not to spend much more than 0.1s in poll_cb
1103 IO::AIO::max_poll_time 0.1;
1104
1105 # use a low priority so other tasks have priority
1106 Event->io (fd => IO::AIO::poll_fileno,
1107 poll => 'r', nice => 1,
1108 cb => &IO::AIO::poll_cb);
1109
550=item IO::AIO::poll_wait 1110=item IO::AIO::poll_wait
551 1111
1112If there are any outstanding requests and none of them in the result
552Wait till the result filehandle becomes ready for reading (simply does a 1113phase, wait till the result filehandle becomes ready for reading (simply
553C<select> on the filehandle. This is useful if you want to synchronously wait 1114does a C<select> on the filehandle. This is useful if you want to
554for some requests to finish). 1115synchronously wait for some requests to finish).
555 1116
556See C<nreqs> for an example. 1117See C<nreqs> for an example.
557 1118
1119=item IO::AIO::poll
1120
1121Waits until some requests have been handled.
1122
1123Returns the number of requests processed, but is otherwise strictly
1124equivalent to:
1125
1126 IO::AIO::poll_wait, IO::AIO::poll_cb
1127
558=item IO::AIO::nreqs 1128=item IO::AIO::flush
559 1129
560Returns the number of requests currently outstanding (i.e. for which their 1130Wait till all outstanding AIO requests have been handled.
561callback has not been invoked yet).
562 1131
563Example: wait till there are no outstanding requests anymore: 1132Strictly equivalent to:
564 1133
565 IO::AIO::poll_wait, IO::AIO::poll_cb 1134 IO::AIO::poll_wait, IO::AIO::poll_cb
566 while IO::AIO::nreqs; 1135 while IO::AIO::nreqs;
567 1136
568=item IO::AIO::flush 1137=back
569 1138
570Wait till all outstanding AIO requests have been handled. 1139=head3 CONTROLLING THE NUMBER OF THREADS
571 1140
572Strictly equivalent to: 1141=over
573
574 IO::AIO::poll_wait, IO::AIO::poll_cb
575 while IO::AIO::nreqs;
576
577=item IO::AIO::poll
578
579Waits until some requests have been handled.
580
581Strictly equivalent to:
582
583 IO::AIO::poll_wait, IO::AIO::poll_cb
584 if IO::AIO::nreqs;
585 1142
586=item IO::AIO::min_parallel $nthreads 1143=item IO::AIO::min_parallel $nthreads
587 1144
588Set the minimum number of AIO threads to C<$nthreads>. The current default 1145Set the minimum number of AIO threads to C<$nthreads>. The current
589is C<4>, which means four asynchronous operations can be done at one time 1146default is C<8>, which means eight asynchronous operations can execute
590(the number of outstanding operations, however, is unlimited). 1147concurrently at any one time (the number of outstanding requests,
1148however, is unlimited).
591 1149
592IO::AIO starts threads only on demand, when an AIO request is queued and 1150IO::AIO starts threads only on demand, when an AIO request is queued and
593no free thread exists. 1151no free thread exists. Please note that queueing up a hundred requests can
1152create demand for a hundred threads, even if it turns out that everything
1153is in the cache and could have been processed faster by a single thread.
594 1154
595It is recommended to keep the number of threads low, as some Linux 1155It is recommended to keep the number of threads relatively low, as some
596kernel versions will scale negatively with the number of threads (higher 1156Linux kernel versions will scale negatively with the number of threads
597parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32 1157(higher parallelity => MUCH higher latency). With current Linux 2.6
598threads should be fine. 1158versions, 4-32 threads should be fine.
599 1159
600Under most circumstances you don't need to call this function, as the 1160Under most circumstances you don't need to call this function, as the
601module selects a default that is suitable for low to moderate load. 1161module selects a default that is suitable for low to moderate load.
602 1162
603=item IO::AIO::max_parallel $nthreads 1163=item IO::AIO::max_parallel $nthreads
612This module automatically runs C<max_parallel 0> at program end, to ensure 1172This module automatically runs C<max_parallel 0> at program end, to ensure
613that all threads are killed and that there are no outstanding requests. 1173that all threads are killed and that there are no outstanding requests.
614 1174
615Under normal circumstances you don't need to call this function. 1175Under normal circumstances you don't need to call this function.
616 1176
1177=item IO::AIO::max_idle $nthreads
1178
1179Limit the number of threads (default: 4) that are allowed to idle (i.e.,
1180threads that did not get a request to process within 10 seconds). That
1181means if a thread becomes idle while C<$nthreads> other threads are also
1182idle, it will free its resources and exit.
1183
1184This is useful when you allow a large number of threads (e.g. 100 or 1000)
1185to allow for extremely high load situations, but want to free resources
1186under normal circumstances (1000 threads can easily consume 30MB of RAM).
1187
1188The default is probably ok in most situations, especially if thread
1189creation is fast. If thread creation is very slow on your system you might
1190want to use larger values.
1191
617=item $oldnreqs = IO::AIO::max_outstanding $nreqs 1192=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
1193
1194This is a very bad function to use in interactive programs because it
1195blocks, and a bad way to reduce concurrency because it is inexact: Better
1196use an C<aio_group> together with a feed callback.
618 1197
619Sets the maximum number of outstanding requests to C<$nreqs>. If you 1198Sets the maximum number of outstanding requests to C<$nreqs>. If you
620try to queue up more than this number of requests, the caller will block until 1199to queue up more than this number of requests, the next call to the
621some requests have been handled. 1200C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1201function will block until the limit is no longer exceeded.
622 1202
623The default is very large, so normally there is no practical limit. If you 1203The default value is very large, so there is no practical limit on the
624queue up many requests in a loop it often improves speed if you set 1204number of outstanding requests.
625this to a relatively low number, such as C<100>.
626 1205
627Under normal circumstances you don't need to call this function. 1206You can still queue as many requests as you want. Therefore,
1207C<max_oustsanding> is mainly useful in simple scripts (with low values) or
1208as a stop gap to shield against fatal memory overflow (with large values).
1209
1210=back
1211
1212=head3 STATISTICAL INFORMATION
1213
1214=over
1215
1216=item IO::AIO::nreqs
1217
1218Returns the number of requests currently in the ready, execute or pending
1219states (i.e. for which their callback has not been invoked yet).
1220
1221Example: wait till there are no outstanding requests anymore:
1222
1223 IO::AIO::poll_wait, IO::AIO::poll_cb
1224 while IO::AIO::nreqs;
1225
1226=item IO::AIO::nready
1227
1228Returns the number of requests currently in the ready state (not yet
1229executed).
1230
1231=item IO::AIO::npending
1232
1233Returns the number of requests currently in the pending state (executed,
1234but not yet processed by poll_cb).
628 1235
629=back 1236=back
630 1237
631=cut 1238=cut
632 1239
644 or return undef; 1251 or return undef;
645 1252
646 *$sym 1253 *$sym
647} 1254}
648 1255
649min_parallel 4; 1256min_parallel 8;
650 1257
651END { 1258END { flush }
652 max_parallel 0;
653}
654 1259
6551; 12601;
656 1261
657=head2 FORK BEHAVIOUR 1262=head2 FORK BEHAVIOUR
658 1263
659This module should do "the right thing" when the process using it forks: 1264This module should do "the right thing" when the process using it forks:
660 1265
661Before the fork, IO::AIO enters a quiescent state where no requests 1266Before the fork, IO::AIO enters a quiescent state where no requests
662can be added in other threads and no results will be processed. After 1267can be added in other threads and no results will be processed. After
663the fork the parent simply leaves the quiescent state and continues 1268the fork the parent simply leaves the quiescent state and continues
664request/result processing, while the child clears the request/result 1269request/result processing, while the child frees the request/result queue
665queue (so the requests started before the fork will only be handled in 1270(so that the requests started before the fork will only be handled in the
666the parent). Threads will be started on demand until the limit ste in the 1271parent). Threads will be started on demand until the limit set in the
667parent process has been reached again. 1272parent process has been reached again.
668 1273
669In short: the parent will, after a short pause, continue as if fork had 1274In short: the parent will, after a short pause, continue as if fork had
670not been called, while the child will act as if IO::AIO has not been used 1275not been called, while the child will act as if IO::AIO has not been used
671yet. 1276yet.
672 1277
1278=head2 MEMORY USAGE
1279
1280Per-request usage:
1281
1282Each aio request uses - depending on your architecture - around 100-200
1283bytes of memory. In addition, stat requests need a stat buffer (possibly
1284a few hundred bytes), readdir requires a result buffer and so on. Perl
1285scalars and other data passed into aio requests will also be locked and
1286will consume memory till the request has entered the done state.
1287
1288This is now awfully much, so queuing lots of requests is not usually a
1289problem.
1290
1291Per-thread usage:
1292
1293In the execution phase, some aio requests require more memory for
1294temporary buffers, and each thread requires a stack and other data
1295structures (usually around 16k-128k, depending on the OS).
1296
1297=head1 KNOWN BUGS
1298
1299Known bugs will be fixed in the next release.
1300
673=head1 SEE ALSO 1301=head1 SEE ALSO
674 1302
675L<Coro>, L<Linux::AIO> (obsolete). 1303L<Coro::AIO>.
676 1304
677=head1 AUTHOR 1305=head1 AUTHOR
678 1306
679 Marc Lehmann <schmorp@schmorp.de> 1307 Marc Lehmann <schmorp@schmorp.de>
680 http://home.schmorp.de/ 1308 http://home.schmorp.de/

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