ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/IO-AIO/README
(Generate patch)

Comparing IO-AIO/README (file contents):
Revision 1.19 by root, Sun Oct 29 01:03:13 2006 UTC vs.
Revision 1.50 by root, Sun Oct 9 08:24:49 2011 UTC

… …
2 IO::AIO - Asynchronous Input/Output 2 IO::AIO - Asynchronous Input/Output
3 3
4SYNOPSIS 4SYNOPSIS
5 use IO::AIO; 5 use IO::AIO;
6 6
7 aio_open "/etc/passwd", O_RDONLY, 0, sub { 7 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
8 my ($fh) = @_; 8 my $fh = shift
9 or die "/etc/passwd: $!";
9 ... 10 ...
10 }; 11 };
11 12
12 aio_unlink "/tmp/file", sub { }; 13 aio_unlink "/tmp/file", sub { };
13 14
… …
23 $req->cancel; # cancel request if still in queue 24 $req->cancel; # cancel request if still in queue
24 25
25 my $grp = aio_group sub { print "all stats done\n" }; 26 my $grp = aio_group sub { print "all stats done\n" };
26 add $grp aio_stat "..." for ...; 27 add $grp aio_stat "..." for ...;
27 28
28 # AnyEvent integration
29 open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
30 my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
31
32 # Event integration
33 Event->io (fd => IO::AIO::poll_fileno,
34 poll => 'r',
35 cb => \&IO::AIO::poll_cb);
36
37 # Glib/Gtk2 integration
38 add_watch Glib::IO IO::AIO::poll_fileno,
39 in => sub { IO::AIO::poll_cb; 1 };
40
41 # Tk integration
42 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
43 readable => \&IO::AIO::poll_cb);
44
45 # Danga::Socket integration
46 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
47 \&IO::AIO::poll_cb);
48
49DESCRIPTION 29DESCRIPTION
50 This module implements asynchronous I/O using whatever means your 30 This module implements asynchronous I/O using whatever means your
51 operating system supports. 31 operating system supports. It is implemented as an interface to "libeio"
32 (<http://software.schmorp.de/pkg/libeio.html>).
52 33
53 Asynchronous means that operations that can normally block your program 34 Asynchronous means that operations that can normally block your program
54 (e.g. reading from disk) will be done asynchronously: the operation will 35 (e.g. reading from disk) will be done asynchronously: the operation will
55 still block, but you can do something else in the meantime. This is 36 still block, but you can do something else in the meantime. This is
56 extremely useful for programs that need to stay interactive even when 37 extremely useful for programs that need to stay interactive even when
… …
58 but can also be used to easily do operations in parallel that are 39 but can also be used to easily do operations in parallel that are
59 normally done sequentially, e.g. stat'ing many files, which is much 40 normally done sequentially, e.g. stat'ing many files, which is much
60 faster on a RAID volume or over NFS when you do a number of stat 41 faster on a RAID volume or over NFS when you do a number of stat
61 operations concurrently. 42 operations concurrently.
62 43
63 While this works on all types of file descriptors (for example sockets), 44 While most of this works on all types of file descriptors (for example
64 using these functions on file descriptors that support nonblocking 45 sockets), using these functions on file descriptors that support
65 operation (again, sockets, pipes etc.) is very inefficient. Use an event 46 nonblocking operation (again, sockets, pipes etc.) is very inefficient.
66 loop for that (such as the Event module): IO::AIO will naturally fit 47 Use an event loop for that (such as the EV module): IO::AIO will
67 into such an event loop itself. 48 naturally fit into such an event loop itself.
68 49
69 In this version, a number of threads are started that execute your 50 In this version, a number of threads are started that execute your
70 requests and signal their completion. You don't need thread support in 51 requests and signal their completion. You don't need thread support in
71 perl, and the threads created by this module will not be visible to 52 perl, and the threads created by this module will not be visible to
72 perl. In the future, this module might make use of the native aio 53 perl. In the future, this module might make use of the native aio
… …
74 not well-supported or restricted (GNU/Linux doesn't allow them on normal 55 not well-supported or restricted (GNU/Linux doesn't allow them on normal
75 files currently, for example), and they would only support aio_read and 56 files currently, for example), and they would only support aio_read and
76 aio_write, so the remaining functionality would have to be implemented 57 aio_write, so the remaining functionality would have to be implemented
77 using threads anyway. 58 using threads anyway.
78 59
79 Although the module will work with in the presence of other (Perl-) 60 Although the module will work in the presence of other (Perl-) threads,
80 threads, it is currently not reentrant in any way, so use appropriate 61 it is currently not reentrant in any way, so use appropriate locking
81 locking yourself, always call "poll_cb" from within the same thread, or 62 yourself, always call "poll_cb" from within the same thread, or never
82 never call "poll_cb" (or other "aio_" functions) recursively. 63 call "poll_cb" (or other "aio_" functions) recursively.
83 64
84 EXAMPLE 65 EXAMPLE
85 This is a simple example that uses the Event module and loads 66 This is a simple example that uses the EV module and loads /etc/passwd
86 /etc/passwd asynchronously: 67 asynchronously:
87 68
88 use Fcntl; 69 use Fcntl;
89 use Event; 70 use EV;
90 use IO::AIO; 71 use IO::AIO;
91 72
92 # register the IO::AIO callback with Event 73 # register the IO::AIO callback with EV
93 Event->io (fd => IO::AIO::poll_fileno, 74 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
94 poll => 'r',
95 cb => \&IO::AIO::poll_cb);
96 75
97 # queue the request to open /etc/passwd 76 # queue the request to open /etc/passwd
98 aio_open "/etc/passwd", O_RDONLY, 0, sub { 77 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
99 my $fh = $_[0] 78 my $fh = shift
100 or die "error while opening: $!"; 79 or die "error while opening: $!";
101 80
102 # stat'ing filehandles is generally non-blocking 81 # stat'ing filehandles is generally non-blocking
103 my $size = -s $fh; 82 my $size = -s $fh;
104 83
… …
112 91
113 # file contents now in $contents 92 # file contents now in $contents
114 print $contents; 93 print $contents;
115 94
116 # exit event loop and program 95 # exit event loop and program
117 Event::unloop; 96 EV::unloop;
118 }; 97 };
119 }; 98 };
120 99
121 # possibly queue up other requests, or open GUI windows, 100 # possibly queue up other requests, or open GUI windows,
122 # check for sockets etc. etc. 101 # check for sockets etc. etc.
123 102
124 # process events as long as there are some: 103 # process events as long as there are some:
125 Event::loop; 104 EV::loop;
126 105
127REQUEST ANATOMY AND LIFETIME 106REQUEST ANATOMY AND LIFETIME
128 Every "aio_*" function creates a request. which is a C data structure 107 Every "aio_*" function creates a request. which is a C data structure
129 not directly visible to Perl. 108 not directly visible to Perl.
130 109
… …
166 anymore (except possibly for the Perl object, but its connection to 145 anymore (except possibly for the Perl object, but its connection to
167 the actual aio request is severed and calling its methods will 146 the actual aio request is severed and calling its methods will
168 either do nothing or result in a runtime error). 147 either do nothing or result in a runtime error).
169 148
170FUNCTIONS 149FUNCTIONS
150 QUICK OVERVIEW
151 This section simply lists the prototypes of the most important functions
152 for quick reference. See the following sections for function-by-function
153 documentation.
154
155 aio_wd $pathname, $callback->($wd)
156 aio_open $pathname, $flags, $mode, $callback->($fh)
157 aio_close $fh, $callback->($status)
158 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
159 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
160 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
161 aio_readahead $fh,$offset,$length, $callback->($retval)
162 aio_stat $fh_or_path, $callback->($status)
163 aio_lstat $fh, $callback->($status)
164 aio_statvfs $fh_or_path, $callback->($statvfs)
165 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
166 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
167 aio_truncate $fh_or_path, $offset, $callback->($status)
168 aio_chmod $fh_or_path, $mode, $callback->($status)
169 aio_unlink $pathname, $callback->($status)
170 aio_mknod $pathname, $mode, $dev, $callback->($status)
171 aio_link $srcpath, $dstpath, $callback->($status)
172 aio_symlink $srcpath, $dstpath, $callback->($status)
173 aio_readlink $pathname, $callback->($link)
174 aio_realpath $pathname, $callback->($link)
175 aio_rename $srcpath, $dstpath, $callback->($status)
176 aio_mkdir $pathname, $mode, $callback->($status)
177 aio_rmdir $pathname, $callback->($status)
178 aio_readdir $pathname, $callback->($entries)
179 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
180 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
181 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
182 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
183 aio_load $pathname, $data, $callback->($status)
184 aio_copy $srcpath, $dstpath, $callback->($status)
185 aio_move $srcpath, $dstpath, $callback->($status)
186 aio_rmtree $pathname, $callback->($status)
187 aio_sync $callback->($status)
188 aio_syncfs $fh, $callback->($status)
189 aio_fsync $fh, $callback->($status)
190 aio_fdatasync $fh, $callback->($status)
191 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
192 aio_pathsync $pathname, $callback->($status)
193 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
194 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
195 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
196 aio_mlockall $flags, $callback->($status)
197 aio_group $callback->(...)
198 aio_nop $callback->()
199
200 $prev_pri = aioreq_pri [$pri]
201 aioreq_nice $pri_adjust
202
203 IO::AIO::poll_wait
204 IO::AIO::poll_cb
205 IO::AIO::poll
206 IO::AIO::flush
207 IO::AIO::max_poll_reqs $nreqs
208 IO::AIO::max_poll_time $seconds
209 IO::AIO::min_parallel $nthreads
210 IO::AIO::max_parallel $nthreads
211 IO::AIO::max_idle $nthreads
212 IO::AIO::idle_timeout $seconds
213 IO::AIO::max_outstanding $maxreqs
214 IO::AIO::nreqs
215 IO::AIO::nready
216 IO::AIO::npending
217
218 IO::AIO::sendfile $ofh, $ifh, $offset, $count
219 IO::AIO::fadvise $fh, $offset, $len, $advice
220 IO::AIO::madvise $scalar, $offset, $length, $advice
221 IO::AIO::mprotect $scalar, $offset, $length, $protect
222 IO::AIO::munlock $scalar, $offset = 0, $length = undef
223 IO::AIO::munlockall
224
171 AIO REQUEST FUNCTIONS 225 AIO REQUEST FUNCTIONS
172 All the "aio_*" calls are more or less thin wrappers around the 226 All the "aio_*" calls are more or less thin wrappers around the syscall
173 syscall with the same name (sans "aio_"). The arguments are similar 227 with the same name (sans "aio_"). The arguments are similar or
174 or identical, and they all accept an additional (and optional) 228 identical, and they all accept an additional (and optional) $callback
175 $callback argument which must be a code reference. This code 229 argument which must be a code reference. This code reference will be
176 reference will get called with the syscall return code (e.g. most 230 called after the syscall has been executed in an asynchronous fashion.
231 The results of the request will be passed as arguments to the callback
232 (and, if an error occured, in $!) - for most requests the syscall return
177 syscalls return -1 on error, unlike perl, which usually delivers 233 code (e.g. most syscalls return -1 on error, unlike perl, which usually
178 "false") as it's sole argument when the given syscall has been 234 delivers "false").
179 executed asynchronously.
180 235
236 Some requests (such as "aio_readdir") pass the actual results and
237 communicate failures by passing "undef".
238
181 All functions expecting a filehandle keep a copy of the filehandle 239 All functions expecting a filehandle keep a copy of the filehandle
182 internally until the request has finished. 240 internally until the request has finished.
183 241
184 All functions return request objects of type IO::AIO::REQ that allow 242 All functions return request objects of type IO::AIO::REQ that allow
185 further manipulation of those requests while they are in-flight. 243 further manipulation of those requests while they are in-flight.
186 244
187 The pathnames you pass to these routines *must* be absolute and 245 The pathnames you pass to these routines *should* be absolute. The
188 encoded as octets. The reason for the former is that at the time the 246 reason for this is that at the time the request is being executed, the
189 request is being executed, the current working directory could have 247 current working directory could have changed. Alternatively, you can
190 changed. Alternatively, you can make sure that you never change the 248 make sure that you never change the current working directory anywhere
191 current working directory anywhere in the program and then use 249 in the program and then use relative paths. You can also take advantage
192 relative paths. 250 of IO::AIOs working directory abstraction, that lets you specify paths
251 relative to some previously-opened "working directory object" - see the
252 description of the "IO::AIO::WD" class later in this document.
193 253
194 To encode pathnames as octets, either make sure you either: a) 254 To encode pathnames as octets, either make sure you either: a) always
195 always pass in filenames you got from outside (command line, readdir 255 pass in filenames you got from outside (command line, readdir etc.)
196 etc.) without tinkering, b) are ASCII or ISO 8859-1, c) use the 256 without tinkering, b) are in your native filesystem encoding, c) use the
197 Encode module and encode your pathnames to the locale (or other) 257 Encode module and encode your pathnames to the locale (or other)
198 encoding in effect in the user environment, d) use 258 encoding in effect in the user environment, d) use
199 Glib::filename_from_unicode on unicode filenames or e) use something 259 Glib::filename_from_unicode on unicode filenames or e) use something
200 else to ensure your scalar has the correct contents. 260 else to ensure your scalar has the correct contents.
201 261
202 This works, btw. independent of the internal UTF-8 bit, which 262 This works, btw. independent of the internal UTF-8 bit, which IO::AIO
203 IO::AIO handles correctly wether it is set or not. 263 handles correctly whether it is set or not.
204 264
205 $prev_pri = aioreq_pri [$pri] 265 $prev_pri = aioreq_pri [$pri]
206 Returns the priority value that would be used for the next 266 Returns the priority value that would be used for the next request
207 request and, if $pri is given, sets the priority for the next 267 and, if $pri is given, sets the priority for the next aio request.
208 aio request.
209 268
210 The default priority is 0, the minimum and maximum priorities 269 The default priority is 0, the minimum and maximum priorities are -4
211 are -4 and 4, respectively. Requests with higher priority will 270 and 4, respectively. Requests with higher priority will be serviced
212 be serviced first. 271 first.
213 272
214 The priority will be reset to 0 after each call to one of the 273 The priority will be reset to 0 after each call to one of the
215 "aio_*" functions. 274 "aio_*" functions.
216 275
217 Example: open a file with low priority, then read something from 276 Example: open a file with low priority, then read something from it
218 it with higher priority so the read request is serviced before 277 with higher priority so the read request is serviced before other
219 other low priority open requests (potentially spamming the 278 low priority open requests (potentially spamming the cache):
220 cache):
221 279
280 aioreq_pri -3;
281 aio_open ..., sub {
282 return unless $_[0];
283
222 aioreq_pri -3; 284 aioreq_pri -2;
223 aio_open ..., sub {
224 return unless $_[0];
225
226 aioreq_pri -2;
227 aio_read $_[0], ..., sub { 285 aio_read $_[0], ..., sub {
228 ...
229 };
230 };
231
232 aioreq_nice $pri_adjust
233 Similar to "aioreq_pri", but subtracts the given value from the
234 current priority, so the effect is cumulative.
235
236 aio_open $pathname, $flags, $mode, $callback->($fh)
237 Asynchronously open or create a file and call the callback with
238 a newly created filehandle for the file.
239
240 The pathname passed to "aio_open" must be absolute. See API
241 NOTES, above, for an explanation.
242
243 The $flags argument is a bitmask. See the "Fcntl" module for a
244 list. They are the same as used by "sysopen".
245
246 Likewise, $mode specifies the mode of the newly created file, if
247 it didn't exist and "O_CREAT" has been given, just like perl's
248 "sysopen", except that it is mandatory (i.e. use 0 if you don't
249 create new files, and 0666 or 0777 if you do).
250
251 Example:
252
253 aio_open "/etc/passwd", O_RDONLY, 0, sub {
254 if ($_[0]) {
255 print "open successful, fh is $_[0]\n";
256 ...
257 } else {
258 die "open failed: $!\n";
259 }
260 };
261
262 aio_close $fh, $callback->($status)
263 Asynchronously close a file and call the callback with the
264 result code. *WARNING:* although accepted, you should not pass
265 in a perl filehandle here, as perl will likely close the file
266 descriptor another time when the filehandle is destroyed.
267 Normally, you can safely call perls "close" or just let
268 filehandles go out of scope.
269
270 This is supposed to be a bug in the API, so that might change.
271 It's therefore best to avoid this function.
272
273 aio_read $fh,$offset,$length, $data,$dataoffset,
274 $callback->($retval)
275 aio_write $fh,$offset,$length, $data,$dataoffset,
276 $callback->($retval)
277 Reads or writes "length" bytes from the specified "fh" and
278 "offset" into the scalar given by "data" and offset "dataoffset"
279 and calls the callback without the actual number of bytes read
280 (or -1 on error, just like the syscall).
281
282 The $data scalar *MUST NOT* be modified in any way while the
283 request is outstanding. Modifying it can result in segfaults or
284 WW3 (if the necessary/optional hardware is installed).
285
286 Example: Read 15 bytes at offset 7 into scalar $buffer, starting
287 at offset 0 within the scalar:
288
289 aio_read $fh, 7, 15, $buffer, 0, sub {
290 $_[0] > 0 or die "read error: $!";
291 print "read $_[0] bytes: <$buffer>\n";
292 };
293
294 aio_sendfile $out_fh, $in_fh, $in_offset, $length,
295 $callback->($retval)
296 Tries to copy $length bytes from $in_fh to $out_fh. It starts
297 reading at byte offset $in_offset, and starts writing at the
298 current file offset of $out_fh. Because of that, it is not safe
299 to issue more than one "aio_sendfile" per $out_fh, as they will
300 interfere with each other.
301
302 This call tries to make use of a native "sendfile" syscall to
303 provide zero-copy operation. For this to work, $out_fh should
304 refer to a socket, and $in_fh should refer to mmap'able file.
305
306 If the native sendfile call fails or is not implemented, it will
307 be emulated, so you can call "aio_sendfile" on any type of
308 filehandle regardless of the limitations of the operating
309 system.
310
311 Please note, however, that "aio_sendfile" can read more bytes
312 from $in_fh than are written, and there is no way to find out
313 how many bytes have been read from "aio_sendfile" alone, as
314 "aio_sendfile" only provides the number of bytes written to
315 $out_fh. Only if the result value equals $length one can assume
316 that $length bytes have been read.
317
318 aio_readahead $fh,$offset,$length, $callback->($retval)
319 "aio_readahead" populates the page cache with data from a file
320 so that subsequent reads from that file will not block on disk
321 I/O. The $offset argument specifies the starting point from
322 which data is to be read and $length specifies the number of
323 bytes to be read. I/O is performed in whole pages, so that
324 offset is effectively rounded down to a page boundary and bytes
325 are read up to the next page boundary greater than or equal to
326 (off-set+length). "aio_readahead" does not read beyond the end
327 of the file. The current file offset of the file is left
328 unchanged.
329
330 If that syscall doesn't exist (likely if your OS isn't Linux) it
331 will be emulated by simply reading the data, which would have a
332 similar effect.
333
334 aio_stat $fh_or_path, $callback->($status)
335 aio_lstat $fh, $callback->($status)
336 Works like perl's "stat" or "lstat" in void context. The
337 callback will be called after the stat and the results will be
338 available using "stat _" or "-s _" etc...
339
340 The pathname passed to "aio_stat" must be absolute. See API
341 NOTES, above, for an explanation.
342
343 Currently, the stats are always 64-bit-stats, i.e. instead of
344 returning an error when stat'ing a large file, the results will
345 be silently truncated unless perl itself is compiled with large
346 file support.
347
348 Example: Print the length of /etc/passwd:
349
350 aio_stat "/etc/passwd", sub {
351 $_[0] and die "stat failed: $!";
352 print "size is ", -s _, "\n";
353 };
354
355 aio_unlink $pathname, $callback->($status)
356 Asynchronously unlink (delete) a file and call the callback with
357 the result code.
358
359 aio_mknod $path, $mode, $dev, $callback->($status)
360 [EXPERIMENTAL]
361
362 Asynchronously create a device node (or fifo). See mknod(2).
363
364 The only (POSIX-) portable way of calling this function is:
365
366 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
367
368 aio_link $srcpath, $dstpath, $callback->($status)
369 Asynchronously create a new link to the existing object at
370 $srcpath at the path $dstpath and call the callback with the
371 result code.
372
373 aio_symlink $srcpath, $dstpath, $callback->($status)
374 Asynchronously create a new symbolic link to the existing object
375 at $srcpath at the path $dstpath and call the callback with the
376 result code.
377
378 aio_rename $srcpath, $dstpath, $callback->($status)
379 Asynchronously rename the object at $srcpath to $dstpath, just
380 as rename(2) and call the callback with the result code.
381
382 aio_rmdir $pathname, $callback->($status)
383 Asynchronously rmdir (delete) a directory and call the callback
384 with the result code.
385
386 aio_readdir $pathname, $callback->($entries)
387 Unlike the POSIX call of the same name, "aio_readdir" reads an
388 entire directory (i.e. opendir + readdir + closedir). The
389 entries will not be sorted, and will NOT include the "." and
390 ".." entries.
391
392 The callback a single argument which is either "undef" or an
393 array-ref with the filenames.
394
395 aio_copy $srcpath, $dstpath, $callback->($status)
396 Try to copy the *file* (directories not supported as either
397 source or destination) from $srcpath to $dstpath and call the
398 callback with the 0 (error) or -1 ok.
399
400 This is a composite request that it creates the destination file
401 with mode 0200 and copies the contents of the source file into
402 it using "aio_sendfile", followed by restoring atime, mtime,
403 access mode and uid/gid, in that order.
404
405 If an error occurs, the partial destination file will be
406 unlinked, if possible, except when setting atime, mtime, access
407 mode and uid/gid, where errors are being ignored.
408
409 aio_move $srcpath, $dstpath, $callback->($status)
410 Try to move the *file* (directories not supported as either
411 source or destination) from $srcpath to $dstpath and call the
412 callback with the 0 (error) or -1 ok.
413
414 This is a composite request that tries to rename(2) the file
415 first. If rename files with "EXDEV", it copies the file with
416 "aio_copy" and, if that is successful, unlinking the $srcpath.
417
418 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
419 Scans a directory (similar to "aio_readdir") but additionally
420 tries to efficiently separate the entries of directory $path
421 into two sets of names, directories you can recurse into
422 (directories), and ones you cannot recurse into (everything
423 else, including symlinks to directories).
424
425 "aio_scandir" is a composite request that creates of many sub
426 requests_ $maxreq specifies the maximum number of outstanding
427 aio requests that this function generates. If it is "<= 0", then
428 a suitable default will be chosen (currently 4).
429
430 On error, the callback is called without arguments, otherwise it
431 receives two array-refs with path-relative entry names.
432
433 Example:
434
435 aio_scandir $dir, 0, sub {
436 my ($dirs, $nondirs) = @_;
437 print "real directories: @$dirs\n";
438 print "everything else: @$nondirs\n";
439 };
440
441 Implementation notes.
442
443 The "aio_readdir" cannot be avoided, but "stat()"'ing every
444 entry can.
445
446 After reading the directory, the modification time, size etc. of
447 the directory before and after the readdir is checked, and if
448 they match (and isn't the current time), the link count will be
449 used to decide how many entries are directories (if >= 2).
450 Otherwise, no knowledge of the number of subdirectories will be
451 assumed.
452
453 Then entries will be sorted into likely directories (everything
454 without a non-initial dot currently) and likely non-directories
455 (everything else). Then every entry plus an appended "/." will
456 be "stat"'ed, likely directories first. If that succeeds, it
457 assumes that the entry is a directory or a symlink to directory
458 (which will be checked seperately). This is often faster than
459 stat'ing the entry itself because filesystems might detect the
460 type of the entry without reading the inode data (e.g. ext2fs
461 filetype feature).
462
463 If the known number of directories (link count - 2) has been
464 reached, the rest of the entries is assumed to be
465 non-directories.
466
467 This only works with certainty on POSIX (= UNIX) filesystems,
468 which fortunately are the vast majority of filesystems around.
469
470 It will also likely work on non-POSIX filesystems with reduced
471 efficiency as those tend to return 0 or 1 as link counts, which
472 disables the directory counting heuristic.
473
474 aio_fsync $fh, $callback->($status)
475 Asynchronously call fsync on the given filehandle and call the
476 callback with the fsync result code.
477
478 aio_fdatasync $fh, $callback->($status)
479 Asynchronously call fdatasync on the given filehandle and call
480 the callback with the fdatasync result code.
481
482 If this call isn't available because your OS lacks it or it
483 couldn't be detected, it will be emulated by calling "fsync"
484 instead.
485
486 aio_group $callback->(...)
487 This is a very special aio request: Instead of doing something,
488 it is a container for other aio requests, which is useful if you
489 want to bundle many requests into a single, composite, request
490 with a definite callback and the ability to cancel the whole
491 request with its subrequests.
492
493 Returns an object of class IO::AIO::GRP. See its documentation
494 below for more info.
495
496 Example:
497
498 my $grp = aio_group sub {
499 print "all stats done\n";
500 };
501
502 add $grp
503 (aio_stat ...),
504 (aio_stat ...),
505 ...; 286 ...
506
507 aio_nop $callback->()
508 This is a special request - it does nothing in itself and is
509 only used for side effects, such as when you want to add a dummy
510 request to a group so that finishing the requests in the group
511 depends on executing the given code.
512
513 While this request does nothing, it still goes through the
514 execution phase and still requires a worker thread. Thus, the
515 callback will not be executed immediately but only after other
516 requests in the queue have entered their execution phase. This
517 can be used to measure request latency.
518
519 IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
520 Mainly used for debugging and benchmarking, this aio request
521 puts one of the request workers to sleep for the given time.
522
523 While it is theoretically handy to have simple I/O scheduling
524 requests like sleep and file handle readable/writable, the
525 overhead this creates is immense (it blocks a thread for a long
526 time) so do not use this function except to put your application
527 under artificial I/O pressure.
528
529 IO::AIO::REQ CLASS
530 All non-aggregate "aio_*" functions return an object of this class
531 when called in non-void context.
532
533 cancel $req
534 Cancels the request, if possible. Has the effect of skipping
535 execution when entering the execute state and skipping calling
536 the callback when entering the the result state, but will leave
537 the request otherwise untouched. That means that requests that
538 currently execute will not be stopped and resources held by the
539 request will not be freed prematurely.
540
541 cb $req $callback->(...)
542 Replace (or simply set) the callback registered to the request.
543
544 IO::AIO::GRP CLASS
545 This class is a subclass of IO::AIO::REQ, so all its methods apply
546 to objects of this class, too.
547
548 A IO::AIO::GRP object is a special request that can contain multiple
549 other aio requests.
550
551 You create one by calling the "aio_group" constructing function with
552 a callback that will be called when all contained requests have
553 entered the "done" state:
554
555 my $grp = aio_group sub {
556 print "all requests are done\n";
557 };
558
559 You add requests by calling the "add" method with one or more
560 "IO::AIO::REQ" objects:
561
562 $grp->add (aio_unlink "...");
563
564 add $grp aio_stat "...", sub {
565 $_[0] or return $grp->result ("error");
566
567 # add another request dynamically, if first succeeded
568 add $grp aio_open "...", sub {
569 $grp->result ("ok");
570 }; 287 };
571 }; 288 };
572 289
290 aioreq_nice $pri_adjust
291 Similar to "aioreq_pri", but subtracts the given value from the
292 current priority, so the effect is cumulative.
293
294 aio_open $pathname, $flags, $mode, $callback->($fh)
295 Asynchronously open or create a file and call the callback with a
296 newly created filehandle for the file.
297
298 The pathname passed to "aio_open" must be absolute. See API NOTES,
299 above, for an explanation.
300
301 The $flags argument is a bitmask. See the "Fcntl" module for a list.
302 They are the same as used by "sysopen".
303
304 Likewise, $mode specifies the mode of the newly created file, if it
305 didn't exist and "O_CREAT" has been given, just like perl's
306 "sysopen", except that it is mandatory (i.e. use 0 if you don't
307 create new files, and 0666 or 0777 if you do). Note that the $mode
308 will be modified by the umask in effect then the request is being
309 executed, so better never change the umask.
310
311 Example:
312
313 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
314 if ($_[0]) {
315 print "open successful, fh is $_[0]\n";
316 ...
317 } else {
318 die "open failed: $!\n";
319 }
320 };
321
322 In addition to all the common open modes/flags ("O_RDONLY",
323 "O_WRONLY", "O_RDWR", "O_CREAT", "O_TRUNC", "O_EXCL" and
324 "O_APPEND"), the following POSIX and non-POSIX constants are
325 available (missing ones on your system are, as usual, 0):
326
327 "O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",
328 "O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",
329 "O_DSYNC", "O_RSYNC", "O_SYNC" and "O_TTY_INIT".
330
331 aio_close $fh, $callback->($status)
332 Asynchronously close a file and call the callback with the result
333 code.
334
335 Unfortunately, you can't do this to perl. Perl *insists* very
336 strongly on closing the file descriptor associated with the
337 filehandle itself.
338
339 Therefore, "aio_close" will not close the filehandle - instead it
340 will use dup2 to overwrite the file descriptor with the write-end of
341 a pipe (the pipe fd will be created on demand and will be cached).
342
343 Or in other words: the file descriptor will be closed, but it will
344 not be free for reuse until the perl filehandle is closed.
345
346 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
347 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
348 Reads or writes $length bytes from or to the specified $fh and
349 $offset into the scalar given by $data and offset $dataoffset and
350 calls the callback without the actual number of bytes read (or -1 on
351 error, just like the syscall).
352
353 "aio_read" will, like "sysread", shrink or grow the $data scalar to
354 offset plus the actual number of bytes read.
355
356 If $offset is undefined, then the current file descriptor offset
357 will be used (and updated), otherwise the file descriptor offset
358 will not be changed by these calls.
359
360 If $length is undefined in "aio_write", use the remaining length of
361 $data.
362
363 If $dataoffset is less than zero, it will be counted from the end of
364 $data.
365
366 The $data scalar *MUST NOT* be modified in any way while the request
367 is outstanding. Modifying it can result in segfaults or World War
368 III (if the necessary/optional hardware is installed).
369
370 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
371 offset 0 within the scalar:
372
373 aio_read $fh, 7, 15, $buffer, 0, sub {
374 $_[0] > 0 or die "read error: $!";
375 print "read $_[0] bytes: <$buffer>\n";
376 };
377
378 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
379 Tries to copy $length bytes from $in_fh to $out_fh. It starts
380 reading at byte offset $in_offset, and starts writing at the current
381 file offset of $out_fh. Because of that, it is not safe to issue
382 more than one "aio_sendfile" per $out_fh, as they will interfere
383 with each other. The same $in_fh works fine though, as this function
384 does not move or use the file offset of $in_fh.
385
386 Please note that "aio_sendfile" can read more bytes from $in_fh than
387 are written, and there is no way to find out how many more bytes
388 have been read from "aio_sendfile" alone, as "aio_sendfile" only
389 provides the number of bytes written to $out_fh. Only if the result
390 value equals $length one can assume that $length bytes have been
391 read.
392
393 Unlike with other "aio_" functions, it makes a lot of sense to use
394 "aio_sendfile" on non-blocking sockets, as long as one end
395 (typically the $in_fh) is a file - the file I/O will then be
396 asynchronous, while the socket I/O will be non-blocking. Note,
397 however, that you can run into a trap where "aio_sendfile" reads
398 some data with readahead, then fails to write all data, and when the
399 socket is ready the next time, the data in the cache is already
400 lost, forcing "aio_sendfile" to again hit the disk. Explicit
401 "aio_read" + "aio_write" let's you better control resource usage.
402
403 This call tries to make use of a native "sendfile"-like syscall to
404 provide zero-copy operation. For this to work, $out_fh should refer
405 to a socket, and $in_fh should refer to an mmap'able file.
406
407 If a native sendfile cannot be found or it fails with "ENOSYS",
408 "EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
409 "ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on
410 any type of filehandle regardless of the limitations of the
411 operating system.
412
413 As native sendfile syscalls (as practically any non-POSIX interface
414 hacked together in a hurry to improve benchmark numbers) tend to be
415 rather buggy on many systems, this implementation tries to work
416 around some known bugs in Linux and FreeBSD kernels (probably
417 others, too), but that might fail, so you really really should check
418 the return value of "aio_sendfile" - fewre bytes than expected might
419 have been transferred.
420
421 aio_readahead $fh,$offset,$length, $callback->($retval)
422 "aio_readahead" populates the page cache with data from a file so
423 that subsequent reads from that file will not block on disk I/O. The
424 $offset argument specifies the starting point from which data is to
425 be read and $length specifies the number of bytes to be read. I/O is
426 performed in whole pages, so that offset is effectively rounded down
427 to a page boundary and bytes are read up to the next page boundary
428 greater than or equal to (off-set+length). "aio_readahead" does not
429 read beyond the end of the file. The current file offset of the file
430 is left unchanged.
431
432 If that syscall doesn't exist (likely if your OS isn't Linux) it
433 will be emulated by simply reading the data, which would have a
434 similar effect.
435
436 aio_stat $fh_or_path, $callback->($status)
437 aio_lstat $fh, $callback->($status)
438 Works like perl's "stat" or "lstat" in void context. The callback
439 will be called after the stat and the results will be available
440 using "stat _" or "-s _" etc...
441
442 The pathname passed to "aio_stat" must be absolute. See API NOTES,
443 above, for an explanation.
444
445 Currently, the stats are always 64-bit-stats, i.e. instead of
446 returning an error when stat'ing a large file, the results will be
447 silently truncated unless perl itself is compiled with large file
448 support.
449
450 To help interpret the mode and dev/rdev stat values, IO::AIO offers
451 the following constants and functions (if not implemented, the
452 constants will be 0 and the functions will either "croak" or fall
453 back on traditional behaviour).
454
455 "S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
456 "S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
457 "IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
458
459 Example: Print the length of /etc/passwd:
460
461 aio_stat "/etc/passwd", sub {
462 $_[0] and die "stat failed: $!";
463 print "size is ", -s _, "\n";
464 };
465
466 aio_statvfs $fh_or_path, $callback->($statvfs)
467 Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
468 whether a file handle or path was passed.
469
470 On success, the callback is passed a hash reference with the
471 following members: "bsize", "frsize", "blocks", "bfree", "bavail",
472 "files", "ffree", "favail", "fsid", "flag" and "namemax". On
473 failure, "undef" is passed.
474
475 The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
476 and "ST_NOSUID".
477
478 The following non-POSIX IO::AIO::ST_* flag masks are defined to
479 their correct value when available, or to 0 on systems that do not
480 support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
481 "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
482 "ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
483
484 Example: stat "/wd" and dump out the data if successful.
485
486 aio_statvfs "/wd", sub {
487 my $f = $_[0]
488 or die "statvfs: $!";
489
490 use Data::Dumper;
491 say Dumper $f;
492 };
493
494 # result:
495 {
496 bsize => 1024,
497 bfree => 4333064312,
498 blocks => 10253828096,
499 files => 2050765568,
500 flag => 4096,
501 favail => 2042092649,
502 bavail => 4333064312,
503 ffree => 2042092649,
504 namemax => 255,
505 frsize => 1024,
506 fsid => 1810
507 }
508
509 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
510 Works like perl's "utime" function (including the special case of
511 $atime and $mtime being undef). Fractional times are supported if
512 the underlying syscalls support them.
513
514 When called with a pathname, uses utimes(2) if available, otherwise
515 utime(2). If called on a file descriptor, uses futimes(2) if
516 available, otherwise returns ENOSYS, so this is not portable.
517
518 Examples:
519
520 # set atime and mtime to current time (basically touch(1)):
521 aio_utime "path", undef, undef;
522 # set atime to current time and mtime to beginning of the epoch:
523 aio_utime "path", time, undef; # undef==0
524
525 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
526 Works like perl's "chown" function, except that "undef" for either
527 $uid or $gid is being interpreted as "do not change" (but -1 can
528 also be used).
529
530 Examples:
531
532 # same as "chown root path" in the shell:
533 aio_chown "path", 0, -1;
534 # same as above:
535 aio_chown "path", 0, undef;
536
537 aio_truncate $fh_or_path, $offset, $callback->($status)
538 Works like truncate(2) or ftruncate(2).
539
540 aio_chmod $fh_or_path, $mode, $callback->($status)
541 Works like perl's "chmod" function.
542
543 aio_unlink $pathname, $callback->($status)
544 Asynchronously unlink (delete) a file and call the callback with the
545 result code.
546
547 aio_mknod $pathname, $mode, $dev, $callback->($status)
548 [EXPERIMENTAL]
549
550 Asynchronously create a device node (or fifo). See mknod(2).
551
552 The only (POSIX-) portable way of calling this function is:
553
554 aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
555
556 See "aio_stat" for info about some potentially helpful extra
557 constants and functions.
558
559 aio_link $srcpath, $dstpath, $callback->($status)
560 Asynchronously create a new link to the existing object at $srcpath
561 at the path $dstpath and call the callback with the result code.
562
563 aio_symlink $srcpath, $dstpath, $callback->($status)
564 Asynchronously create a new symbolic link to the existing object at
565 $srcpath at the path $dstpath and call the callback with the result
566 code.
567
568 aio_readlink $pathname, $callback->($link)
569 Asynchronously read the symlink specified by $path and pass it to
570 the callback. If an error occurs, nothing or undef gets passed to
571 the callback.
572
573 aio_realpath $pathname, $callback->($path)
574 Asynchronously make the path absolute and resolve any symlinks in
575 $path. The resulting path only consists of directories (Same as
576 Cwd::realpath).
577
578 This request can be used to get the absolute path of the current
579 working directory by passing it a path of . (a single dot).
580
581 aio_rename $srcpath, $dstpath, $callback->($status)
582 Asynchronously rename the object at $srcpath to $dstpath, just as
583 rename(2) and call the callback with the result code.
584
585 aio_mkdir $pathname, $mode, $callback->($status)
586 Asynchronously mkdir (create) a directory and call the callback with
587 the result code. $mode will be modified by the umask at the time the
588 request is executed, so do not change your umask.
589
590 aio_rmdir $pathname, $callback->($status)
591 Asynchronously rmdir (delete) a directory and call the callback with
592 the result code.
593
594 aio_readdir $pathname, $callback->($entries)
595 Unlike the POSIX call of the same name, "aio_readdir" reads an
596 entire directory (i.e. opendir + readdir + closedir). The entries
597 will not be sorted, and will NOT include the "." and ".." entries.
598
599 The callback is passed a single argument which is either "undef" or
600 an array-ref with the filenames.
601
602 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
603 Quite similar to "aio_readdir", but the $flags argument allows one
604 to tune behaviour and output format. In case of an error, $entries
605 will be "undef".
606
607 The flags are a combination of the following constants, ORed
608 together (the flags will also be passed to the callback, possibly
609 modified):
610
611 IO::AIO::READDIR_DENTS
612 When this flag is off, then the callback gets an arrayref
613 consisting of names only (as with "aio_readdir"), otherwise it
614 gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
615 describing a single directory entry in more detail.
616
617 $name is the name of the entry.
618
619 $type is one of the "IO::AIO::DT_xxx" constants:
620
621 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
622 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
623 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
624
625 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
626 you need to know, you have to run stat yourself. Also, for speed
627 reasons, the $type scalars are read-only: you can not modify
628 them.
629
630 $inode is the inode number (which might not be exact on systems
631 with 64 bit inode numbers and 32 bit perls). This field has
632 unspecified content on systems that do not deliver the inode
633 information.
634
635 IO::AIO::READDIR_DIRS_FIRST
636 When this flag is set, then the names will be returned in an
637 order where likely directories come first, in optimal stat
638 order. This is useful when you need to quickly find directories,
639 or you want to find all directories while avoiding to stat()
640 each entry.
641
642 If the system returns type information in readdir, then this is
643 used to find directories directly. Otherwise, likely directories
644 are names beginning with ".", or otherwise names with no dots,
645 of which names with short names are tried first.
646
647 IO::AIO::READDIR_STAT_ORDER
648 When this flag is set, then the names will be returned in an
649 order suitable for stat()'ing each one. That is, when you plan
650 to stat() all files in the given directory, then the returned
651 order will likely be fastest.
652
653 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
654 specified, then the likely dirs come first, resulting in a less
655 optimal stat order.
656
657 IO::AIO::READDIR_FOUND_UNKNOWN
658 This flag should not be set when calling "aio_readdirx".
659 Instead, it is being set by "aio_readdirx", when any of the
660 $type's found were "IO::AIO::DT_UNKNOWN". The absence of this
661 flag therefore indicates that all $type's are known, which can
662 be used to speed up some algorithms.
663
664 aio_load $pathname, $data, $callback->($status)
665 This is a composite request that tries to fully load the given file
666 into memory. Status is the same as with aio_read.
667
668 aio_copy $srcpath, $dstpath, $callback->($status)
669 Try to copy the *file* (directories not supported as either source
670 or destination) from $srcpath to $dstpath and call the callback with
671 a status of 0 (ok) or -1 (error, see $!).
672
673 This is a composite request that creates the destination file with
674 mode 0200 and copies the contents of the source file into it using
675 "aio_sendfile", followed by restoring atime, mtime, access mode and
676 uid/gid, in that order.
677
678 If an error occurs, the partial destination file will be unlinked,
679 if possible, except when setting atime, mtime, access mode and
680 uid/gid, where errors are being ignored.
681
682 aio_move $srcpath, $dstpath, $callback->($status)
683 Try to move the *file* (directories not supported as either source
684 or destination) from $srcpath to $dstpath and call the callback with
685 a status of 0 (ok) or -1 (error, see $!).
686
687 This is a composite request that tries to rename(2) the file first;
688 if rename fails with "EXDEV", it copies the file with "aio_copy"
689 and, if that is successful, unlinks the $srcpath.
690
691 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
692 Scans a directory (similar to "aio_readdir") but additionally tries
693 to efficiently separate the entries of directory $path into two sets
694 of names, directories you can recurse into (directories), and ones
695 you cannot recurse into (everything else, including symlinks to
696 directories).
697
698 "aio_scandir" is a composite request that creates of many sub
699 requests_ $maxreq specifies the maximum number of outstanding aio
700 requests that this function generates. If it is "<= 0", then a
701 suitable default will be chosen (currently 4).
702
703 On error, the callback is called without arguments, otherwise it
704 receives two array-refs with path-relative entry names.
705
706 Example:
707
708 aio_scandir $dir, 0, sub {
709 my ($dirs, $nondirs) = @_;
710 print "real directories: @$dirs\n";
711 print "everything else: @$nondirs\n";
712 };
713
714 Implementation notes.
715
716 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
717 can.
718
719 If readdir returns file type information, then this is used directly
720 to find directories.
721
722 Otherwise, after reading the directory, the modification time, size
723 etc. of the directory before and after the readdir is checked, and
724 if they match (and isn't the current time), the link count will be
725 used to decide how many entries are directories (if >= 2).
726 Otherwise, no knowledge of the number of subdirectories will be
727 assumed.
728
729 Then entries will be sorted into likely directories a non-initial
730 dot currently) and likely non-directories (see "aio_readdirx"). Then
731 every entry plus an appended "/." will be "stat"'ed, likely
732 directories first, in order of their inode numbers. If that
733 succeeds, it assumes that the entry is a directory or a symlink to
734 directory (which will be checked separately). This is often faster
735 than stat'ing the entry itself because filesystems might detect the
736 type of the entry without reading the inode data (e.g. ext2fs
737 filetype feature), even on systems that cannot return the filetype
738 information on readdir.
739
740 If the known number of directories (link count - 2) has been
741 reached, the rest of the entries is assumed to be non-directories.
742
743 This only works with certainty on POSIX (= UNIX) filesystems, which
744 fortunately are the vast majority of filesystems around.
745
746 It will also likely work on non-POSIX filesystems with reduced
747 efficiency as those tend to return 0 or 1 as link counts, which
748 disables the directory counting heuristic.
749
750 aio_rmtree $pathname, $callback->($status)
751 Delete a directory tree starting (and including) $path, return the
752 status of the final "rmdir" only. This is a composite request that
753 uses "aio_scandir" to recurse into and rmdir directories, and unlink
754 everything else.
755
756 aio_sync $callback->($status)
757 Asynchronously call sync and call the callback when finished.
758
759 aio_fsync $fh, $callback->($status)
760 Asynchronously call fsync on the given filehandle and call the
761 callback with the fsync result code.
762
763 aio_fdatasync $fh, $callback->($status)
764 Asynchronously call fdatasync on the given filehandle and call the
765 callback with the fdatasync result code.
766
767 If this call isn't available because your OS lacks it or it couldn't
768 be detected, it will be emulated by calling "fsync" instead.
769
770 aio_syncfs $fh, $callback->($status)
771 Asynchronously call the syncfs syscall to sync the filesystem
772 associated to the given filehandle and call the callback with the
773 syncfs result code. If syncfs is not available, calls sync(), but
774 returns -1 and sets errno to "ENOSYS" nevertheless.
775
776 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
777 Sync the data portion of the file specified by $offset and $length
778 to disk (but NOT the metadata), by calling the Linux-specific
779 sync_file_range call. If sync_file_range is not available or it
780 returns ENOSYS, then fdatasync or fsync is being substituted.
781
782 $flags can be a combination of
783 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
784 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
785 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
786 manpage for details.
787
788 aio_pathsync $pathname, $callback->($status)
789 This request tries to open, fsync and close the given path. This is
790 a composite request intended to sync directories after directory
791 operations (E.g. rename). This might not work on all operating
792 systems or have any specific effect, but usually it makes sure that
793 directory changes get written to disc. It works for anything that
794 can be opened for read-only, not just directories.
795
796 Future versions of this function might fall back to other methods
797 when "fsync" on the directory fails (such as calling "sync").
798
799 Passes 0 when everything went ok, and -1 on error.
800
801 aio_msync $scalar, $offset = 0, $length = undef, flags = 0,
802 $callback->($status)
803 This is a rather advanced IO::AIO call, which only works on
804 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
805 also works on data scalars managed by the Sys::Mmap or Mmap modules,
806 note that the scalar must only be modified in-place while an aio
807 operation is pending on it).
808
809 It calls the "msync" function of your OS, if available, with the
810 memory area starting at $offset in the string and ending $length
811 bytes later. If $length is negative, counts from the end, and if
812 $length is "undef", then it goes till the end of the string. The
813 flags can be a combination of "IO::AIO::MS_ASYNC",
814 "IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC".
815
816 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
817 $callback->($status)
818 This is a rather advanced IO::AIO call, which works best on
819 mmap(2)ed scalars.
820
821 It touches (reads or writes) all memory pages in the specified range
822 inside the scalar. All caveats and parameters are the same as for
823 "aio_msync", above, except for flags, which must be either 0 (which
824 reads all pages and ensures they are instantiated) or
825 "IO::AIO::MT_MODIFY", which modifies the memory page s(by reading
826 and writing an octet from it, which dirties the page).
827
828 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
829 This is a rather advanced IO::AIO call, which works best on
830 mmap(2)ed scalars.
831
832 It reads in all the pages of the underlying storage into memory (if
833 any) and locks them, so they are not getting swapped/paged out or
834 removed.
835
836 If $length is undefined, then the scalar will be locked till the
837 end.
838
839 On systems that do not implement "mlock", this function returns -1
840 and sets errno to "ENOSYS".
841
842 Note that the corresponding "munlock" is synchronous and is
843 documented under "MISCELLANEOUS FUNCTIONS".
844
845 Example: open a file, mmap and mlock it - both will be undone when
846 $data gets destroyed.
847
848 open my $fh, "<", $path or die "$path: $!";
849 my $data;
850 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
851 aio_mlock $data; # mlock in background
852
853 aio_mlockall $flags, $callback->($status)
854 Calls the "mlockall" function with the given $flags (a combination
855 of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
856
857 On systems that do not implement "mlockall", this function returns
858 -1 and sets errno to "ENOSYS".
859
860 Note that the corresponding "munlockall" is synchronous and is
861 documented under "MISCELLANEOUS FUNCTIONS".
862
863 Example: asynchronously lock all current and future pages into
864 memory.
865
866 aio_mlockall IO::AIO::MCL_FUTURE;
867
868 aio_group $callback->(...)
869 This is a very special aio request: Instead of doing something, it
870 is a container for other aio requests, which is useful if you want
871 to bundle many requests into a single, composite, request with a
872 definite callback and the ability to cancel the whole request with
873 its subrequests.
874
875 Returns an object of class IO::AIO::GRP. See its documentation below
876 for more info.
877
878 Example:
879
880 my $grp = aio_group sub {
881 print "all stats done\n";
882 };
883
884 add $grp
885 (aio_stat ...),
886 (aio_stat ...),
887 ...;
888
889 aio_nop $callback->()
890 This is a special request - it does nothing in itself and is only
891 used for side effects, such as when you want to add a dummy request
892 to a group so that finishing the requests in the group depends on
893 executing the given code.
894
895 While this request does nothing, it still goes through the execution
896 phase and still requires a worker thread. Thus, the callback will
897 not be executed immediately but only after other requests in the
898 queue have entered their execution phase. This can be used to
899 measure request latency.
900
901 IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
902 Mainly used for debugging and benchmarking, this aio request puts
903 one of the request workers to sleep for the given time.
904
905 While it is theoretically handy to have simple I/O scheduling
906 requests like sleep and file handle readable/writable, the overhead
907 this creates is immense (it blocks a thread for a long time) so do
908 not use this function except to put your application under
909 artificial I/O pressure.
910
911 IO::AIO::WD - multiple working directories
912 Your process only has one current working directory, which is used by
913 all threads. This makes it hard to use relative paths (some other
914 component could call "chdir" at any time, and it is hard to control when
915 the path will be used by IO::AIO).
916
917 One solution for this is to always use absolute paths. This usually
918 works, but can be quite slow (the kernel has to walk the whole path on
919 every access), and can also be a hassle to implement.
920
921 Newer POSIX systems have a number of functions (openat, fdopendir,
922 futimensat and so on) that make it possible to specify working
923 directories per operation.
924
925 For portability, and because the clowns who "designed", or shall I
926 write, perpetrated this new interface were obviously half-drunk, this
927 abstraction cannot be perfect, though.
928
929 IO::AIO allows you to convert directory paths into a so-called
930 IO::AIO::WD object. This object stores the canonicalised, absolute
931 version of the path, and on systems that allow it, also a directory file
932 descriptor.
933
934 Everywhere where a pathname is accepted by IO::AIO (e.g. in "aio_stat"
935 or "aio_unlink"), one can specify an array reference with an IO::AIO::WD
936 object and a pathname instead (or the IO::AIO::WD object alone, which
937 gets interpreted as "[$wd, "."]"). If the pathname is absolute, the
938 IO::AIO::WD object is ignored, otherwise the pathname is resolved
939 relative to that IO::AIO::WD object.
940
941 For example, to get a wd object for /etc and then stat passwd inside,
942 you would write:
943
944 aio_wd "/etc", sub {
945 my $etcdir = shift;
946
947 # although $etcdir can be undef on error, there is generally no reason
948 # to check for errors here, as aio_stat will fail with ENOENT
949 # when $etcdir is undef.
950
951 aio_stat [$etcdir, "passwd"], sub {
952 # yay
953 };
954 };
955
956 That "aio_wd" is a request and not a normal function shows that creating
957 an IO::AIO::WD object is itself a potentially blocking operation, which
958 is why it is done asynchronously.
959
960 To stat the directory obtained with "aio_wd" above, one could write
961 either of the following three request calls:
962
963 aio_lstat "/etc" , sub { ... # pathname as normal string
964 aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
965 aio_lstat $wd , sub { ... # shorthand for the previous
966
967 As with normal pathnames, IO::AIO keeps a copy of the working directory
968 object and the pathname string, so you could write the following without
969 causing any issues due to $path getting reused:
970
971 my $path = [$wd, undef];
972
973 for my $name (qw(abc def ghi)) {
974 $path->[1] = $name;
975 aio_stat $path, sub {
976 # ...
977 };
978 }
979
980 There are some caveats: when directories get renamed (or deleted), the
981 pathname string doesn't change, so will point to the new directory (or
982 nowhere at all), while the directory fd, if available on the system,
983 will still point to the original directory. Most functions accepting a
984 pathname will use the directory fd on newer systems, and the string on
985 older systems. Some functions (such as realpath) will always rely on the
986 string form of the pathname.
987
988 So this fucntionality is mainly useful to get some protection against
989 "chdir", to easily get an absolute path out of a relative path for
990 future reference, and to speed up doing many operations in the same
991 directory (e.g. when stat'ing all files in a directory).
992
993 The following functions implement this working directory abstraction:
994
995 aio_wd $pathname, $callback->($wd)
996 Asynchonously canonicalise the given pathname and convert it to an
997 IO::AIO::WD object representing it. If possible and supported on the
998 system, also open a directory fd to speed up pathname resolution
999 relative to this working directory.
1000
1001 If something goes wrong, then "undef" is passwd to the callback
1002 instead of a working directory object and $! is set appropriately.
1003 Since passing "undef" as working directory component of a pathname
1004 fails the request with "ENOENT", there is often no need for error
1005 checking in the "aio_wd" callback, as future requests using the
1006 value will fail in the expected way.
1007
1008 If this call isn't available because your OS lacks it or it couldn't
1009 be detected, it will be emulated by calling "fsync" instead.
1010
1011 IO::AIO::CWD
1012 This is a compiletime constant (object) that represents the process
1013 current working directory.
1014
1015 Specifying this object as working directory object for a pathname is
1016 as if the pathname would be specified directly, without a directory
1017 object, e.g., these calls are functionally identical:
1018
1019 aio_stat "somefile", sub { ... };
1020 aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
1021
1022 IO::AIO::REQ CLASS
1023 All non-aggregate "aio_*" functions return an object of this class when
1024 called in non-void context.
1025
1026 cancel $req
1027 Cancels the request, if possible. Has the effect of skipping
1028 execution when entering the execute state and skipping calling the
1029 callback when entering the the result state, but will leave the
1030 request otherwise untouched (with the exception of readdir). That
1031 means that requests that currently execute will not be stopped and
1032 resources held by the request will not be freed prematurely.
1033
1034 cb $req $callback->(...)
1035 Replace (or simply set) the callback registered to the request.
1036
1037 IO::AIO::GRP CLASS
1038 This class is a subclass of IO::AIO::REQ, so all its methods apply to
1039 objects of this class, too.
1040
1041 A IO::AIO::GRP object is a special request that can contain multiple
1042 other aio requests.
1043
1044 You create one by calling the "aio_group" constructing function with a
1045 callback that will be called when all contained requests have entered
1046 the "done" state:
1047
1048 my $grp = aio_group sub {
1049 print "all requests are done\n";
1050 };
1051
1052 You add requests by calling the "add" method with one or more
1053 "IO::AIO::REQ" objects:
1054
1055 $grp->add (aio_unlink "...");
1056
1057 add $grp aio_stat "...", sub {
1058 $_[0] or return $grp->result ("error");
1059
1060 # add another request dynamically, if first succeeded
1061 add $grp aio_open "...", sub {
1062 $grp->result ("ok");
1063 };
1064 };
1065
573 This makes it very easy to create composite requests (see the source 1066 This makes it very easy to create composite requests (see the source of
574 of "aio_move" for an application) that work and feel like simple 1067 "aio_move" for an application) that work and feel like simple requests.
575 requests.
576 1068
577 * The IO::AIO::GRP objects will be cleaned up during calls to 1069 * The IO::AIO::GRP objects will be cleaned up during calls to
578 "IO::AIO::poll_cb", just like any other request. 1070 "IO::AIO::poll_cb", just like any other request.
1071
579 * They can be canceled like any other request. Canceling will cancel 1072 * They can be canceled like any other request. Canceling will cancel
580 not only the request itself, but also all requests it contains. 1073 not only the request itself, but also all requests it contains.
1074
581 * They can also can also be added to other IO::AIO::GRP objects. 1075 * They can also can also be added to other IO::AIO::GRP objects.
1076
582 * You must not add requests to a group from within the group 1077 * You must not add requests to a group from within the group callback
583 callback (or any later time). 1078 (or any later time).
584 1079
585 Their lifetime, simplified, looks like this: when they are empty, 1080 Their lifetime, simplified, looks like this: when they are empty, they
586 they will finish very quickly. If they contain only requests that 1081 will finish very quickly. If they contain only requests that are in the
587 are in the "done" state, they will also finish. Otherwise they will 1082 "done" state, they will also finish. Otherwise they will continue to
588 continue to exist. 1083 exist.
589 1084
590 That means after creating a group you have some time to add 1085 That means after creating a group you have some time to add requests
1086 (precisely before the callback has been invoked, which is only done
591 requests. And in the callbacks of those requests, you can add 1087 within the "poll_cb"). And in the callbacks of those requests, you can
592 further requests to the group. And only when all those requests have 1088 add further requests to the group. And only when all those requests have
593 finished will the the group itself finish. 1089 finished will the the group itself finish.
594 1090
595 add $grp ... 1091 add $grp ...
596 $grp->add (...) 1092 $grp->add (...)
597 Add one or more requests to the group. Any type of IO::AIO::REQ 1093 Add one or more requests to the group. Any type of IO::AIO::REQ can
598 can be added, including other groups, as long as you do not 1094 be added, including other groups, as long as you do not create
599 create circular dependencies. 1095 circular dependencies.
600 1096
601 Returns all its arguments. 1097 Returns all its arguments.
602 1098
603 $grp->cancel_subs 1099 $grp->cancel_subs
604 Cancel all subrequests and clears any feeder, but not the group 1100 Cancel all subrequests and clears any feeder, but not the group
605 request itself. Useful when you queued a lot of events but got a 1101 request itself. Useful when you queued a lot of events but got a
606 result early. 1102 result early.
607 1103
1104 The group request will finish normally (you cannot add requests to
1105 the group).
1106
608 $grp->result (...) 1107 $grp->result (...)
609 Set the result value(s) that will be passed to the group 1108 Set the result value(s) that will be passed to the group callback
610 callback when all subrequests have finished and set thre groups 1109 when all subrequests have finished and set the groups errno to the
611 errno to the current value of errno (just like calling "errno" 1110 current value of errno (just like calling "errno" without an error
612 without an error number). By default, no argument will be passed 1111 number). By default, no argument will be passed and errno is zero.
613 and errno is zero.
614 1112
615 $grp->errno ([$errno]) 1113 $grp->errno ([$errno])
616 Sets the group errno value to $errno, or the current value of 1114 Sets the group errno value to $errno, or the current value of errno
617 errno when the argument is missing. 1115 when the argument is missing.
618 1116
619 Every aio request has an associated errno value that is restored 1117 Every aio request has an associated errno value that is restored
620 when the callback is invoked. This method lets you change this 1118 when the callback is invoked. This method lets you change this value
621 value from its default (0). 1119 from its default (0).
622 1120
623 Calling "result" will also set errno, so make sure you either 1121 Calling "result" will also set errno, so make sure you either set $!
624 set $! before the call to "result", or call c<errno> after it. 1122 before the call to "result", or call c<errno> after it.
625 1123
626 feed $grp $callback->($grp) 1124 feed $grp $callback->($grp)
627 Sets a feeder/generator on this group: every group can have an 1125 Sets a feeder/generator on this group: every group can have an
628 attached generator that generates requests if idle. The idea 1126 attached generator that generates requests if idle. The idea behind
629 behind this is that, although you could just queue as many 1127 this is that, although you could just queue as many requests as you
630 requests as you want in a group, this might starve other 1128 want in a group, this might starve other requests for a potentially
631 requests for a potentially long time. For example, "aio_scandir" 1129 long time. For example, "aio_scandir" might generate hundreds of
632 might generate hundreds of thousands "aio_stat" requests, 1130 thousands of "aio_stat" requests, delaying any later requests for a
633 delaying any later requests for a long time. 1131 long time.
634 1132
635 To avoid this, and allow incremental generation of requests, you 1133 To avoid this, and allow incremental generation of requests, you can
636 can instead a group and set a feeder on it that generates those 1134 instead a group and set a feeder on it that generates those
637 requests. The feed callback will be called whenever there are 1135 requests. The feed callback will be called whenever there are few
638 few enough (see "limit", below) requests active in the group 1136 enough (see "limit", below) requests active in the group itself and
639 itself and is expected to queue more requests. 1137 is expected to queue more requests.
640 1138
641 The feed callback can queue as many requests as it likes (i.e. 1139 The feed callback can queue as many requests as it likes (i.e. "add"
642 "add" does not impose any limits). 1140 does not impose any limits).
643 1141
644 If the feed does not queue more requests when called, it will be 1142 If the feed does not queue more requests when called, it will be
645 automatically removed from the group. 1143 automatically removed from the group.
646 1144
647 If the feed limit is 0, it will be set to 2 automatically. 1145 If the feed limit is 0 when this method is called, it will be set to
1146 2 automatically.
648 1147
649 Example: 1148 Example:
650 1149
651 # stat all files in @files, but only ever use four aio requests concurrently: 1150 # stat all files in @files, but only ever use four aio requests concurrently:
652 1151
653 my $grp = aio_group sub { print "finished\n" }; 1152 my $grp = aio_group sub { print "finished\n" };
654 limit $grp 4; 1153 limit $grp 4;
655 feed $grp sub { 1154 feed $grp sub {
656 my $file = pop @files 1155 my $file = pop @files
657 or return; 1156 or return;
658 1157
659 add $grp aio_stat $file, sub { ... }; 1158 add $grp aio_stat $file, sub { ... };
660 }; 1159 };
661 1160
662 limit $grp $num 1161 limit $grp $num
663 Sets the feeder limit for the group: The feeder will be called 1162 Sets the feeder limit for the group: The feeder will be called
664 whenever the group contains less than this many requests. 1163 whenever the group contains less than this many requests.
665 1164
666 Setting the limit to 0 will pause the feeding process. 1165 Setting the limit to 0 will pause the feeding process.
1166
1167 The default value for the limit is 0, but note that setting a feeder
1168 automatically bumps it up to 2.
667 1169
668 SUPPORT FUNCTIONS 1170 SUPPORT FUNCTIONS
669 EVENT PROCESSING AND EVENT LOOP INTEGRATION 1171 EVENT PROCESSING AND EVENT LOOP INTEGRATION
670 $fileno = IO::AIO::poll_fileno 1172 $fileno = IO::AIO::poll_fileno
671 Return the *request result pipe file descriptor*. This 1173 Return the *request result pipe file descriptor*. This filehandle
672 filehandle must be polled for reading by some mechanism outside 1174 must be polled for reading by some mechanism outside this module
673 this module (e.g. Event or select, see below or the SYNOPSIS). 1175 (e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
674 If the pipe becomes readable you have to call "poll_cb" to check 1176 pipe becomes readable you have to call "poll_cb" to check the
675 the results. 1177 results.
676 1178
677 See "poll_cb" for an example. 1179 See "poll_cb" for an example.
678 1180
679 IO::AIO::poll_cb 1181 IO::AIO::poll_cb
680 Process some outstanding events on the result pipe. You have to 1182 Process some outstanding events on the result pipe. You have to call
681 call this regularly. Returns the number of events processed. 1183 this regularly. Returns 0 if all events could be processed (or there
1184 were no events to process), or -1 if it returned earlier for
682 Returns immediately when no events are outstanding. The amount 1185 whatever reason. Returns immediately when no events are outstanding.
683 of events processed depends on the settings of 1186 The amount of events processed depends on the settings of
684 "IO::AIO::max_poll_req" and "IO::AIO::max_poll_time". 1187 "IO::AIO::max_poll_req" and "IO::AIO::max_poll_time".
685 1188
686 If not all requests were processed for whatever reason, the 1189 If not all requests were processed for whatever reason, the
687 filehandle will still be ready when "poll_cb" returns. 1190 filehandle will still be ready when "poll_cb" returns, so normally
1191 you don't have to do anything special to have it called later.
688 1192
1193 Apart from calling "IO::AIO::poll_cb" when the event filehandle
1194 becomes ready, it can be beneficial to call this function from loops
1195 which submit a lot of requests, to make sure the results get
1196 processed when they become available and not just when the loop is
1197 finished and the event loop takes over again. This function returns
1198 very fast when there are no outstanding requests.
1199
689 Example: Install an Event watcher that automatically calls 1200 Example: Install an Event watcher that automatically calls
690 IO::AIO::poll_cb with high priority: 1201 IO::AIO::poll_cb with high priority (more examples can be found in
1202 the SYNOPSIS section, at the top of this document):
691 1203
692 Event->io (fd => IO::AIO::poll_fileno, 1204 Event->io (fd => IO::AIO::poll_fileno,
693 poll => 'r', async => 1, 1205 poll => 'r', async => 1,
694 cb => \&IO::AIO::poll_cb); 1206 cb => \&IO::AIO::poll_cb);
695 1207
696 IO::AIO::max_poll_reqs $nreqs
697 IO::AIO::max_poll_time $seconds
698 These set the maximum number of requests (default 0, meaning
699 infinity) that are being processed by "IO::AIO::poll_cb" in one
700 call, respectively the maximum amount of time (default 0,
701 meaning infinity) spent in "IO::AIO::poll_cb" to process
702 requests (more correctly the mininum amount of time "poll_cb" is
703 allowed to use).
704
705 Setting these is useful if you want to ensure some level of
706 interactiveness when perl is not fast enough to process all
707 requests in time.
708
709 For interactive programs, values such as 0.01 to 0.1 should be
710 fine.
711
712 Example: Install an Event watcher that automatically calls
713 IO::AIO::poll_some with low priority, to ensure that other parts
714 of the program get the CPU sometimes even under high AIO load.
715
716 # try not to spend much more than 0.1s in poll_cb
717 IO::AIO::max_poll_time 0.1;
718
719 # use a low priority so other tasks have priority
720 Event->io (fd => IO::AIO::poll_fileno,
721 poll => 'r', nice => 1,
722 cb => &IO::AIO::poll_cb);
723
724 IO::AIO::poll_wait 1208 IO::AIO::poll_wait
1209 If there are any outstanding requests and none of them in the result
725 Wait till the result filehandle becomes ready for reading 1210 phase, wait till the result filehandle becomes ready for reading
726 (simply does a "select" on the filehandle. This is useful if you 1211 (simply does a "select" on the filehandle. This is useful if you
727 want to synchronously wait for some requests to finish). 1212 want to synchronously wait for some requests to finish).
728 1213
729 See "nreqs" for an example. 1214 See "nreqs" for an example.
730 1215
731 IO::AIO::poll 1216 IO::AIO::poll
732 Waits until some requests have been handled. 1217 Waits until some requests have been handled.
733 1218
1219 Returns the number of requests processed, but is otherwise strictly
734 Strictly equivalent to: 1220 equivalent to:
735 1221
736 IO::AIO::poll_wait, IO::AIO::poll_cb 1222 IO::AIO::poll_wait, IO::AIO::poll_cb
737 if IO::AIO::nreqs;
738 1223
739 IO::AIO::flush 1224 IO::AIO::flush
740 Wait till all outstanding AIO requests have been handled. 1225 Wait till all outstanding AIO requests have been handled.
741 1226
742 Strictly equivalent to: 1227 Strictly equivalent to:
743 1228
744 IO::AIO::poll_wait, IO::AIO::poll_cb 1229 IO::AIO::poll_wait, IO::AIO::poll_cb
745 while IO::AIO::nreqs; 1230 while IO::AIO::nreqs;
1231
1232 IO::AIO::max_poll_reqs $nreqs
1233 IO::AIO::max_poll_time $seconds
1234 These set the maximum number of requests (default 0, meaning
1235 infinity) that are being processed by "IO::AIO::poll_cb" in one
1236 call, respectively the maximum amount of time (default 0, meaning
1237 infinity) spent in "IO::AIO::poll_cb" to process requests (more
1238 correctly the mininum amount of time "poll_cb" is allowed to use).
1239
1240 Setting "max_poll_time" to a non-zero value creates an overhead of
1241 one syscall per request processed, which is not normally a problem
1242 unless your callbacks are really really fast or your OS is really
1243 really slow (I am not mentioning Solaris here). Using
1244 "max_poll_reqs" incurs no overhead.
1245
1246 Setting these is useful if you want to ensure some level of
1247 interactiveness when perl is not fast enough to process all requests
1248 in time.
1249
1250 For interactive programs, values such as 0.01 to 0.1 should be fine.
1251
1252 Example: Install an Event watcher that automatically calls
1253 IO::AIO::poll_cb with low priority, to ensure that other parts of
1254 the program get the CPU sometimes even under high AIO load.
1255
1256 # try not to spend much more than 0.1s in poll_cb
1257 IO::AIO::max_poll_time 0.1;
1258
1259 # use a low priority so other tasks have priority
1260 Event->io (fd => IO::AIO::poll_fileno,
1261 poll => 'r', nice => 1,
1262 cb => &IO::AIO::poll_cb);
746 1263
747 CONTROLLING THE NUMBER OF THREADS 1264 CONTROLLING THE NUMBER OF THREADS
748 IO::AIO::min_parallel $nthreads 1265 IO::AIO::min_parallel $nthreads
749 Set the minimum number of AIO threads to $nthreads. The current 1266 Set the minimum number of AIO threads to $nthreads. The current
750 default is 8, which means eight asynchronous operations can 1267 default is 8, which means eight asynchronous operations can execute
751 execute concurrently at any one time (the number of outstanding 1268 concurrently at any one time (the number of outstanding requests,
752 requests, however, is unlimited). 1269 however, is unlimited).
753 1270
754 IO::AIO starts threads only on demand, when an AIO request is 1271 IO::AIO starts threads only on demand, when an AIO request is queued
755 queued and no free thread exists. Please note that queueing up a 1272 and no free thread exists. Please note that queueing up a hundred
756 hundred requests can create demand for a hundred threads, even 1273 requests can create demand for a hundred threads, even if it turns
757 if it turns out that everything is in the cache and could have 1274 out that everything is in the cache and could have been processed
758 been processed faster by a single thread. 1275 faster by a single thread.
759 1276
760 It is recommended to keep the number of threads relatively low, 1277 It is recommended to keep the number of threads relatively low, as
761 as some Linux kernel versions will scale negatively with the 1278 some Linux kernel versions will scale negatively with the number of
762 number of threads (higher parallelity => MUCH higher latency). 1279 threads (higher parallelity => MUCH higher latency). With current
763 With current Linux 2.6 versions, 4-32 threads should be fine. 1280 Linux 2.6 versions, 4-32 threads should be fine.
764 1281
765 Under most circumstances you don't need to call this function, 1282 Under most circumstances you don't need to call this function, as
766 as the module selects a default that is suitable for low to 1283 the module selects a default that is suitable for low to moderate
767 moderate load. 1284 load.
768 1285
769 IO::AIO::max_parallel $nthreads 1286 IO::AIO::max_parallel $nthreads
770 Sets the maximum number of AIO threads to $nthreads. If more 1287 Sets the maximum number of AIO threads to $nthreads. If more than
771 than the specified number of threads are currently running, this 1288 the specified number of threads are currently running, this function
772 function kills them. This function blocks until the limit is 1289 kills them. This function blocks until the limit is reached.
773 reached.
774 1290
775 While $nthreads are zero, aio requests get queued but not 1291 While $nthreads are zero, aio requests get queued but not executed
776 executed until the number of threads has been increased again. 1292 until the number of threads has been increased again.
777 1293
778 This module automatically runs "max_parallel 0" at program end, 1294 This module automatically runs "max_parallel 0" at program end, to
779 to ensure that all threads are killed and that there are no 1295 ensure that all threads are killed and that there are no outstanding
780 outstanding requests. 1296 requests.
781 1297
782 Under normal circumstances you don't need to call this function. 1298 Under normal circumstances you don't need to call this function.
783 1299
784 IO::AIO::max_idle $nthreads 1300 IO::AIO::max_idle $nthreads
785 Limit the number of threads (default: 4) that are allowed to 1301 Limit the number of threads (default: 4) that are allowed to idle
786 idle (i.e., threads that did not get a request to process within 1302 (i.e., threads that did not get a request to process within the idle
787 10 seconds). That means if a thread becomes idle while $nthreads 1303 timeout (default: 10 seconds). That means if a thread becomes idle
788 other threads are also idle, it will free its resources and 1304 while $nthreads other threads are also idle, it will free its
789 exit. 1305 resources and exit.
790 1306
791 This is useful when you allow a large number of threads (e.g. 1307 This is useful when you allow a large number of threads (e.g. 100 or
792 100 or 1000) to allow for extremely high load situations, but 1308 1000) to allow for extremely high load situations, but want to free
793 want to free resources under normal circumstances (1000 threads 1309 resources under normal circumstances (1000 threads can easily
794 can easily consume 30MB of RAM). 1310 consume 30MB of RAM).
795 1311
796 The default is probably ok in most situations, especially if 1312 The default is probably ok in most situations, especially if thread
797 thread creation is fast. If thread creation is very slow on your 1313 creation is fast. If thread creation is very slow on your system you
798 system you might want to use larger values. 1314 might want to use larger values.
799 1315
1316 IO::AIO::idle_timeout $seconds
1317 Sets the minimum idle timeout (default 10) after which worker
1318 threads are allowed to exit. SEe "IO::AIO::max_idle".
1319
800 $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1320 IO::AIO::max_outstanding $maxreqs
801 This is a very bad function to use in interactive programs
802 because it blocks, and a bad way to reduce concurrency because
803 it is inexact: Better use an "aio_group" together with a feed
804 callback.
805
806 Sets the maximum number of outstanding requests to $nreqs. If 1321 Sets the maximum number of outstanding requests to $nreqs. If you do
807 you to queue up more than this number of requests, the next call 1322 queue up more than this number of requests, the next call to
808 to the "poll_cb" (and "poll_some" and other functions calling 1323 "IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
809 "poll_cb") function will block until the limit is no longer 1324 "IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
810 exceeded. 1325 no longer exceeded.
811 1326
812 The default value is very large, so there is no practical limit 1327 In other words, this setting does not enforce a queue limit, but can
1328 be used to make poll functions block if the limit is exceeded.
1329
1330 This is a very bad function to use in interactive programs because
1331 it blocks, and a bad way to reduce concurrency because it is
1332 inexact: Better use an "aio_group" together with a feed callback.
1333
1334 It's main use is in scripts without an event loop - when you want to
1335 stat a lot of files, you can write somehting like this:
1336
1337 IO::AIO::max_outstanding 32;
1338
1339 for my $path (...) {
1340 aio_stat $path , ...;
1341 IO::AIO::poll_cb;
1342 }
1343
1344 IO::AIO::flush;
1345
1346 The call to "poll_cb" inside the loop will normally return
1347 instantly, but as soon as more thna 32 reqeusts are in-flight, it
1348 will block until some requests have been handled. This keeps the
1349 loop from pushing a large number of "aio_stat" requests onto the
1350 queue.
1351
1352 The default value for "max_outstanding" is very large, so there is
813 on the number of outstanding requests. 1353 no practical limit on the number of outstanding requests.
814
815 You can still queue as many requests as you want. Therefore,
816 "max_oustsanding" is mainly useful in simple scripts (with low
817 values) or as a stop gap to shield against fatal memory overflow
818 (with large values).
819 1354
820 STATISTICAL INFORMATION 1355 STATISTICAL INFORMATION
821 IO::AIO::nreqs 1356 IO::AIO::nreqs
822 Returns the number of requests currently in the ready, execute 1357 Returns the number of requests currently in the ready, execute or
823 or pending states (i.e. for which their callback has not been 1358 pending states (i.e. for which their callback has not been invoked
824 invoked yet). 1359 yet).
825 1360
826 Example: wait till there are no outstanding requests anymore: 1361 Example: wait till there are no outstanding requests anymore:
827 1362
828 IO::AIO::poll_wait, IO::AIO::poll_cb 1363 IO::AIO::poll_wait, IO::AIO::poll_cb
829 while IO::AIO::nreqs; 1364 while IO::AIO::nreqs;
830 1365
831 IO::AIO::nready 1366 IO::AIO::nready
832 Returns the number of requests currently in the ready state (not 1367 Returns the number of requests currently in the ready state (not yet
833 yet executed). 1368 executed).
834 1369
835 IO::AIO::npending 1370 IO::AIO::npending
836 Returns the number of requests currently in the pending state 1371 Returns the number of requests currently in the pending state
837 (executed, but not yet processed by poll_cb). 1372 (executed, but not yet processed by poll_cb).
1373
1374 MISCELLANEOUS FUNCTIONS
1375 IO::AIO implements some functions that might be useful, but are not
1376 asynchronous.
1377
1378 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1379 Calls the "eio_sendfile_sync" function, which is like
1380 "aio_sendfile", but is blocking (this makes most sense if you know
1381 the input data is likely cached already and the output filehandle is
1382 set to non-blocking operations).
1383
1384 Returns the number of bytes copied, or -1 on error.
1385
1386 IO::AIO::fadvise $fh, $offset, $len, $advice
1387 Simply calls the "posix_fadvise" function (see its manpage for
1388 details). The following advice constants are available:
1389 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1390 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1391 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1392
1393 On systems that do not implement "posix_fadvise", this function
1394 returns ENOSYS, otherwise the return value of "posix_fadvise".
1395
1396 IO::AIO::madvise $scalar, $offset, $len, $advice
1397 Simply calls the "posix_madvise" function (see its manpage for
1398 details). The following advice constants are available:
1399 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1400 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1401 "IO::AIO::MADV_DONTNEED".
1402
1403 On systems that do not implement "posix_madvise", this function
1404 returns ENOSYS, otherwise the return value of "posix_madvise".
1405
1406 IO::AIO::mprotect $scalar, $offset, $len, $protect
1407 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1408 $scalar (see its manpage for details). The following protect
1409 constants are available: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1410 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1411
1412 On systems that do not implement "mprotect", this function returns
1413 ENOSYS, otherwise the return value of "mprotect".
1414
1415 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1416 Memory-maps a file (or anonymous memory range) and attaches it to
1417 the given $scalar, which will act like a string scalar.
1418
1419 The only operations allowed on the scalar are "substr"/"vec" that
1420 don't change the string length, and most read-only operations such
1421 as copying it or searching it with regexes and so on.
1422
1423 Anything else is unsafe and will, at best, result in memory leaks.
1424
1425 The memory map associated with the $scalar is automatically removed
1426 when the $scalar is destroyed, or when the "IO::AIO::mmap" or
1427 "IO::AIO::munmap" functions are called.
1428
1429 This calls the "mmap"(2) function internally. See your system's
1430 manual page for details on the $length, $prot and $flags parameters.
1431
1432 The $length must be larger than zero and smaller than the actual
1433 filesize.
1434
1435 $prot is a combination of "IO::AIO::PROT_NONE",
1436 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1437 "IO::AIO::PROT_WRITE",
1438
1439 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1440 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1441 not available, the are defined as 0): "IO::AIO::MAP_ANONYMOUS"
1442 (which is set to "MAP_ANON" if your system only provides this
1443 constant), "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED",
1444 "IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or
1445 "IO::AIO::MAP_NONBLOCK"
1446
1447 If $fh is "undef", then a file descriptor of -1 is passed.
1448
1449 $offset is the offset from the start of the file - it generally must
1450 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
1451
1452 Example:
1453
1454 use Digest::MD5;
1455 use IO::AIO;
1456
1457 open my $fh, "<verybigfile"
1458 or die "$!";
1459
1460 IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
1461 or die "verybigfile: $!";
1462
1463 my $fast_md5 = md5 $data;
1464
1465 IO::AIO::munmap $scalar
1466 Removes a previous mmap and undefines the $scalar.
1467
1468 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1469 Calls the "munlock" function, undoing the effects of a previous
1470 "aio_mlock" call (see its description for details).
1471
1472 IO::AIO::munlockall
1473 Calls the "munlockall" function.
1474
1475 On systems that do not implement "munlockall", this function returns
1476 ENOSYS, otherwise the return value of "munlockall".
1477
1478EVENT LOOP INTEGRATION
1479 It is recommended to use AnyEvent::AIO to integrate IO::AIO
1480 automatically into many event loops:
1481
1482 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
1483 use AnyEvent::AIO;
1484
1485 You can also integrate IO::AIO manually into many event loops, here are
1486 some examples of how to do this:
1487
1488 # EV integration
1489 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
1490
1491 # Event integration
1492 Event->io (fd => IO::AIO::poll_fileno,
1493 poll => 'r',
1494 cb => \&IO::AIO::poll_cb);
1495
1496 # Glib/Gtk2 integration
1497 add_watch Glib::IO IO::AIO::poll_fileno,
1498 in => sub { IO::AIO::poll_cb; 1 };
1499
1500 # Tk integration
1501 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
1502 readable => \&IO::AIO::poll_cb);
1503
1504 # Danga::Socket integration
1505 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1506 \&IO::AIO::poll_cb);
838 1507
839 FORK BEHAVIOUR 1508 FORK BEHAVIOUR
840 This module should do "the right thing" when the process using it 1509 Usage of pthreads in a program changes the semantics of fork
841 forks: 1510 considerably. Specifically, only async-safe functions can be called
1511 after fork. Perl doesn't know about this, so in general, you cannot call
1512 fork with defined behaviour in perl if pthreads are involved. IO::AIO
1513 uses pthreads, so this applies, but many other extensions and (for
1514 inexplicable reasons) perl itself often is linked against pthreads, so
1515 this limitation applies to quite a lot of perls.
842 1516
843 Before the fork, IO::AIO enters a quiescent state where no requests 1517 This module no longer tries to fight your OS, or POSIX. That means
844 can be added in other threads and no results will be processed. 1518 IO::AIO only works in the process that loaded it. Forking is fully
845 After the fork the parent simply leaves the quiescent state and 1519 supported, but using IO::AIO in the child is not.
846 continues request/result processing, while the child frees the
847 request/result queue (so that the requests started before the fork
848 will only be handled in the parent). Threads will be started on
849 demand until the limit set in the parent process has been reached
850 again.
851 1520
852 In short: the parent will, after a short pause, continue as if fork 1521 You might get around by not *using* IO::AIO before (or after) forking.
853 had not been called, while the child will act as if IO::AIO has not 1522 You could also try to call the IO::AIO::reinit function in the child:
854 been used yet. 1523
1524 IO::AIO::reinit
1525 Abandons all current requests and I/O threads and simply
1526 reinitialises all data structures. This is not an operation
1527 supported by any standards, but happens to work on GNU/Linux and
1528 some newer BSD systems.
1529
1530 The only reasonable use for this function is to call it after
1531 forking, if "IO::AIO" was used in the parent. Calling it while
1532 IO::AIO is active in the process will result in undefined behaviour.
1533 Calling it at any time will also result in any undefined (by POSIX)
1534 behaviour.
855 1535
856 MEMORY USAGE 1536 MEMORY USAGE
857 Per-request usage: 1537 Per-request usage:
858 1538
859 Each aio request uses - depending on your architecture - around 1539 Each aio request uses - depending on your architecture - around 100-200
860 100-200 bytes of memory. In addition, stat requests need a stat 1540 bytes of memory. In addition, stat requests need a stat buffer (possibly
861 buffer (possibly a few hundred bytes), readdir requires a result 1541 a few hundred bytes), readdir requires a result buffer and so on. Perl
862 buffer and so on. Perl scalars and other data passed into aio 1542 scalars and other data passed into aio requests will also be locked and
863 requests will also be locked and will consume memory till the 1543 will consume memory till the request has entered the done state.
864 request has entered the done state.
865 1544
866 This is now awfully much, so queuing lots of requests is not usually 1545 This is not awfully much, so queuing lots of requests is not usually a
867 a problem. 1546 problem.
868 1547
869 Per-thread usage: 1548 Per-thread usage:
870 1549
871 In the execution phase, some aio requests require more memory for 1550 In the execution phase, some aio requests require more memory for
872 temporary buffers, and each thread requires a stack and other data 1551 temporary buffers, and each thread requires a stack and other data
873 structures (usually around 16k-128k, depending on the OS). 1552 structures (usually around 16k-128k, depending on the OS).
874 1553
875KNOWN BUGS 1554KNOWN BUGS
876 Known bugs will be fixed in the next release. 1555 Known bugs will be fixed in the next release.
877 1556
878SEE ALSO 1557SEE ALSO
879 Coro::AIO. 1558 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
1559 more natural syntax.
880 1560
881AUTHOR 1561AUTHOR
882 Marc Lehmann <schmorp@schmorp.de> 1562 Marc Lehmann <schmorp@schmorp.de>
883 http://home.schmorp.de/ 1563 http://home.schmorp.de/
884 1564

Diff Legend

– Removed lines
+ Added lines
< Changed lines
> Changed lines