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Revision 1.45 by root, Thu Dec 30 07:19:31 2010 UTC

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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
14 aio_read $fh, 30000, 1024, $buffer, 0, sub { 15 aio_read $fh, 30000, 1024, $buffer, 0, sub {
15 $_[0] > 0 or die "read error: $!"; 16 $_[0] > 0 or die "read error: $!";
16 }; 17 };
17 18
18 # AnyEvent 19 # version 2+ has request and group objects
19 open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!"; 20 use IO::AIO 2;
20 my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
21 21
22 # Event 22 aioreq_pri 4; # give next request a very high priority
23 Event->io (fd => IO::AIO::poll_fileno, 23 my $req = aio_unlink "/tmp/file", sub { };
24 poll => 'r', 24 $req->cancel; # cancel request if still in queue
25 cb => \&IO::AIO::poll_cb);
26 25
27 # Glib/Gtk2 26 my $grp = aio_group sub { print "all stats done\n" };
28 add_watch Glib::IO IO::AIO::poll_fileno, 27 add $grp aio_stat "..." for ...;
29 in => sub { IO::AIO::poll_cb; 1 };
30
31 # Tk
32 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
33 readable => \&IO::AIO::poll_cb);
34
35 # Danga::Socket
36 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
37 \&IO::AIO::poll_cb);
38 28
39DESCRIPTION 29DESCRIPTION
40 This module implements asynchronous I/O using whatever means your 30 This module implements asynchronous I/O using whatever means your
41 operating system supports. 31 operating system supports. It is implemented as an interface to "libeio"
32 (<http://software.schmorp.de/pkg/libeio.html>).
42 33
34 Asynchronous means that operations that can normally block your program
35 (e.g. reading from disk) will be done asynchronously: the operation will
36 still block, but you can do something else in the meantime. This is
37 extremely useful for programs that need to stay interactive even when
38 doing heavy I/O (GUI programs, high performance network servers etc.),
39 but can also be used to easily do operations in parallel that are
40 normally done sequentially, e.g. stat'ing many files, which is much
41 faster on a RAID volume or over NFS when you do a number of stat
42 operations concurrently.
43
44 While most of this works on all types of file descriptors (for example
45 sockets), using these functions on file descriptors that support
46 nonblocking operation (again, sockets, pipes etc.) is very inefficient.
47 Use an event loop for that (such as the EV module): IO::AIO will
48 naturally fit into such an event loop itself.
49
43 Currently, a number of threads are started that execute your read/writes 50 In this version, a number of threads are started that execute your
44 and signal their completion. You don't need thread support in your libc 51 requests and signal their completion. You don't need thread support in
45 or 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
46 the pthreads library. In the future, this module might make use of the 53 perl. In the future, this module might make use of the native aio
47 native aio functions available on many operating systems. However, they 54 functions available on many operating systems. However, they are often
48 are often not well-supported (Linux doesn't allow them on normal files 55 not well-supported or restricted (GNU/Linux doesn't allow them on normal
49 currently, for example), and they would only support aio_read and 56 files currently, for example), and they would only support aio_read and
50 aio_write, so the remaining functionality would have to be implemented 57 aio_write, so the remaining functionality would have to be implemented
51 using threads anyway. 58 using threads anyway.
52 59
53 Although the module will work with in the presence of other threads, it 60 Although the module will work in the presence of other (Perl-) threads,
54 is currently not reentrant, so use appropriate locking yourself, always 61 it is currently not reentrant in any way, so use appropriate locking
55 call "poll_cb" from within the same thread, or never call "poll_cb" (or 62 yourself, always call "poll_cb" from within the same thread, or never
56 other "aio_" functions) recursively. 63 call "poll_cb" (or other "aio_" functions) recursively.
64
65 EXAMPLE
66 This is a simple example that uses the EV module and loads /etc/passwd
67 asynchronously:
68
69 use Fcntl;
70 use EV;
71 use IO::AIO;
72
73 # register the IO::AIO callback with EV
74 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
75
76 # queue the request to open /etc/passwd
77 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
78 my $fh = shift
79 or die "error while opening: $!";
80
81 # stat'ing filehandles is generally non-blocking
82 my $size = -s $fh;
83
84 # queue a request to read the file
85 my $contents;
86 aio_read $fh, 0, $size, $contents, 0, sub {
87 $_[0] == $size
88 or die "short read: $!";
89
90 close $fh;
91
92 # file contents now in $contents
93 print $contents;
94
95 # exit event loop and program
96 EV::unloop;
97 };
98 };
99
100 # possibly queue up other requests, or open GUI windows,
101 # check for sockets etc. etc.
102
103 # process events as long as there are some:
104 EV::loop;
105
106REQUEST ANATOMY AND LIFETIME
107 Every "aio_*" function creates a request. which is a C data structure
108 not directly visible to Perl.
109
110 If called in non-void context, every request function returns a Perl
111 object representing the request. In void context, nothing is returned,
112 which saves a bit of memory.
113
114 The perl object is a fairly standard ref-to-hash object. The hash
115 contents are not used by IO::AIO so you are free to store anything you
116 like in it.
117
118 During their existance, aio requests travel through the following
119 states, in order:
120
121 ready
122 Immediately after a request is created it is put into the ready
123 state, waiting for a thread to execute it.
124
125 execute
126 A thread has accepted the request for processing and is currently
127 executing it (e.g. blocking in read).
128
129 pending
130 The request has been executed and is waiting for result processing.
131
132 While request submission and execution is fully asynchronous, result
133 processing is not and relies on the perl interpreter calling
134 "poll_cb" (or another function with the same effect).
135
136 result
137 The request results are processed synchronously by "poll_cb".
138
139 The "poll_cb" function will process all outstanding aio requests by
140 calling their callbacks, freeing memory associated with them and
141 managing any groups they are contained in.
142
143 done
144 Request has reached the end of its lifetime and holds no resources
145 anymore (except possibly for the Perl object, but its connection to
146 the actual aio request is severed and calling its methods will
147 either do nothing or result in a runtime error).
57 148
58FUNCTIONS 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_open $pathname, $flags, $mode, $callback->($fh)
156 aio_close $fh, $callback->($status)
157 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
158 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
159 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
160 aio_readahead $fh,$offset,$length, $callback->($retval)
161 aio_stat $fh_or_path, $callback->($status)
162 aio_lstat $fh, $callback->($status)
163 aio_statvfs $fh_or_path, $callback->($statvfs)
164 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
165 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
166 aio_truncate $fh_or_path, $offset, $callback->($status)
167 aio_chmod $fh_or_path, $mode, $callback->($status)
168 aio_unlink $pathname, $callback->($status)
169 aio_mknod $path, $mode, $dev, $callback->($status)
170 aio_link $srcpath, $dstpath, $callback->($status)
171 aio_symlink $srcpath, $dstpath, $callback->($status)
172 aio_readlink $path, $callback->($link)
173 aio_rename $srcpath, $dstpath, $callback->($status)
174 aio_mkdir $pathname, $mode, $callback->($status)
175 aio_rmdir $pathname, $callback->($status)
176 aio_readdir $pathname, $callback->($entries)
177 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
178 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
179 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
180 aio_load $path, $data, $callback->($status)
181 aio_copy $srcpath, $dstpath, $callback->($status)
182 aio_move $srcpath, $dstpath, $callback->($status)
183 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
184 aio_rmtree $path, $callback->($status)
185 aio_sync $callback->($status)
186 aio_fsync $fh, $callback->($status)
187 aio_fdatasync $fh, $callback->($status)
188 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
189 aio_pathsync $path, $callback->($status)
190 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
191 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
192 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
193 aio_mlockall $flags, $callback->($status)
194 aio_group $callback->(...)
195 aio_nop $callback->()
196
197 $prev_pri = aioreq_pri [$pri]
198 aioreq_nice $pri_adjust
199
200 IO::AIO::poll_wait
201 IO::AIO::poll_cb
202 IO::AIO::poll
203 IO::AIO::flush
204 IO::AIO::max_poll_reqs $nreqs
205 IO::AIO::max_poll_time $seconds
206 IO::AIO::min_parallel $nthreads
207 IO::AIO::max_parallel $nthreads
208 IO::AIO::max_idle $nthreads
209 IO::AIO::max_outstanding $maxreqs
210 IO::AIO::nreqs
211 IO::AIO::nready
212 IO::AIO::npending
213
214 IO::AIO::sendfile $ofh, $ifh, $offset, $count
215 IO::AIO::fadvise $fh, $offset, $len, $advice
216 IO::AIO::madvise $scalar, $offset, $length, $advice
217 IO::AIO::mprotect $scalar, $offset, $length, $protect
218 IO::AIO::munlock $scalar, $offset = 0, $length = undef
219 IO::AIO::munlockall
220
59 AIO FUNCTIONS 221 AIO REQUEST FUNCTIONS
60 All the "aio_*" calls are more or less thin wrappers around the syscall 222 All the "aio_*" calls are more or less thin wrappers around the syscall
61 with the same name (sans "aio_"). The arguments are similar or 223 with the same name (sans "aio_"). The arguments are similar or
62 identical, and they all accept an additional (and optional) $callback 224 identical, and they all accept an additional (and optional) $callback
63 argument which must be a code reference. This code reference will get 225 argument which must be a code reference. This code reference will get
64 called with the syscall return code (e.g. most syscalls return -1 on 226 called with the syscall return code (e.g. most syscalls return -1 on
65 error, unlike perl, which usually delivers "false") as it's sole 227 error, unlike perl, which usually delivers "false") as its sole argument
66 argument when the given syscall has been executed asynchronously. 228 after the given syscall has been executed asynchronously.
67 229
68 All functions expecting a filehandle keep a copy of the filehandle 230 All functions expecting a filehandle keep a copy of the filehandle
69 internally until the request has finished. 231 internally until the request has finished.
70 232
233 All functions return request objects of type IO::AIO::REQ that allow
234 further manipulation of those requests while they are in-flight.
235
71 The pathnames you pass to these routines *must* be absolute and encoded 236 The pathnames you pass to these routines *must* be absolute and encoded
72 in byte form. The reason for the former is that at the time the request 237 as octets. The reason for the former is that at the time the request is
73 is being executed, the current working directory could have changed. 238 being executed, the current working directory could have changed.
74 Alternatively, you can make sure that you never change the current 239 Alternatively, you can make sure that you never change the current
75 working directory. 240 working directory anywhere in the program and then use relative paths.
76 241
77 To encode pathnames to byte form, either make sure you either: a) always 242 To encode pathnames as octets, either make sure you either: a) always
78 pass in filenames you got from outside (command line, readdir etc.), b) 243 pass in filenames you got from outside (command line, readdir etc.)
79 are ASCII or ISO 8859-1, c) use the Encode module and encode your 244 without tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module
80 pathnames to the locale (or other) encoding in effect in the user 245 and encode your pathnames to the locale (or other) encoding in effect in
81 environment, d) use Glib::filename_from_unicode on unicode filenames or 246 the user environment, d) use Glib::filename_from_unicode on unicode
82 e) use something else. 247 filenames or e) use something else to ensure your scalar has the correct
248 contents.
249
250 This works, btw. independent of the internal UTF-8 bit, which IO::AIO
251 handles correctly whether it is set or not.
252
253 $prev_pri = aioreq_pri [$pri]
254 Returns the priority value that would be used for the next request
255 and, if $pri is given, sets the priority for the next aio request.
256
257 The default priority is 0, the minimum and maximum priorities are -4
258 and 4, respectively. Requests with higher priority will be serviced
259 first.
260
261 The priority will be reset to 0 after each call to one of the
262 "aio_*" functions.
263
264 Example: open a file with low priority, then read something from it
265 with higher priority so the read request is serviced before other
266 low priority open requests (potentially spamming the cache):
267
268 aioreq_pri -3;
269 aio_open ..., sub {
270 return unless $_[0];
271
272 aioreq_pri -2;
273 aio_read $_[0], ..., sub {
274 ...
275 };
276 };
277
278 aioreq_nice $pri_adjust
279 Similar to "aioreq_pri", but subtracts the given value from the
280 current priority, so the effect is cumulative.
83 281
84 aio_open $pathname, $flags, $mode, $callback->($fh) 282 aio_open $pathname, $flags, $mode, $callback->($fh)
85 Asynchronously open or create a file and call the callback with a 283 Asynchronously open or create a file and call the callback with a
86 newly created filehandle for the file. 284 newly created filehandle for the file.
87 285
… …
92 They are the same as used by "sysopen". 290 They are the same as used by "sysopen".
93 291
94 Likewise, $mode specifies the mode of the newly created file, if it 292 Likewise, $mode specifies the mode of the newly created file, if it
95 didn't exist and "O_CREAT" has been given, just like perl's 293 didn't exist and "O_CREAT" has been given, just like perl's
96 "sysopen", except that it is mandatory (i.e. use 0 if you don't 294 "sysopen", except that it is mandatory (i.e. use 0 if you don't
97 create new files, and 0666 or 0777 if you do). 295 create new files, and 0666 or 0777 if you do). Note that the $mode
296 will be modified by the umask in effect then the request is being
297 executed, so better never change the umask.
98 298
99 Example: 299 Example:
100 300
101 aio_open "/etc/passwd", O_RDONLY, 0, sub { 301 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
102 if ($_[0]) { 302 if ($_[0]) {
103 print "open successful, fh is $_[0]\n"; 303 print "open successful, fh is $_[0]\n";
104 ... 304 ...
105 } else { 305 } else {
106 die "open failed: $!\n"; 306 die "open failed: $!\n";
107 } 307 }
108 }; 308 };
109 309
110 aio_close $fh, $callback->($status) 310 aio_close $fh, $callback->($status)
111 Asynchronously close a file and call the callback with the result 311 Asynchronously close a file and call the callback with the result
112 code. *WARNING:* although accepted, you should not pass in a perl 312 code.
113 filehandle here, as perl will likely close the file descriptor
114 another time when the filehandle is destroyed. Normally, you can
115 safely call perls "close" or just let filehandles go out of scope.
116 313
117 This is supposed to be a bug in the API, so that might change. It's 314 Unfortunately, you can't do this to perl. Perl *insists* very
118 therefore best to avoid this function. 315 strongly on closing the file descriptor associated with the
316 filehandle itself.
317
318 Therefore, "aio_close" will not close the filehandle - instead it
319 will use dup2 to overwrite the file descriptor with the write-end of
320 a pipe (the pipe fd will be created on demand and will be cached).
321
322 Or in other words: the file descriptor will be closed, but it will
323 not be free for reuse until the perl filehandle is closed.
119 324
120 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 325 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
121 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 326 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
122 Reads or writes "length" bytes from the specified "fh" and "offset" 327 Reads or writes $length bytes from or to the specified $fh and
123 into the scalar given by "data" and offset "dataoffset" and calls 328 $offset into the scalar given by $data and offset $dataoffset and
124 the callback without the actual number of bytes read (or -1 on 329 calls the callback without the actual number of bytes read (or -1 on
125 error, just like the syscall). 330 error, just like the syscall).
126 331
332 "aio_read" will, like "sysread", shrink or grow the $data scalar to
333 offset plus the actual number of bytes read.
334
335 If $offset is undefined, then the current file descriptor offset
336 will be used (and updated), otherwise the file descriptor offset
337 will not be changed by these calls.
338
339 If $length is undefined in "aio_write", use the remaining length of
340 $data.
341
342 If $dataoffset is less than zero, it will be counted from the end of
343 $data.
344
127 The $data scalar *MUST NOT* be modified in any way while the request 345 The $data scalar *MUST NOT* be modified in any way while the request
128 is outstanding. Modifying it can result in segfaults or WW3 (if the 346 is outstanding. Modifying it can result in segfaults or World War
129 necessary/optional hardware is installed). 347 III (if the necessary/optional hardware is installed).
130 348
131 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at 349 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
132 offset 0 within the scalar: 350 offset 0 within the scalar:
133 351
134 aio_read $fh, 7, 15, $buffer, 0, sub { 352 aio_read $fh, 7, 15, $buffer, 0, sub {
… …
141 reading at byte offset $in_offset, and starts writing at the current 359 reading at byte offset $in_offset, and starts writing at the current
142 file offset of $out_fh. Because of that, it is not safe to issue 360 file offset of $out_fh. Because of that, it is not safe to issue
143 more than one "aio_sendfile" per $out_fh, as they will interfere 361 more than one "aio_sendfile" per $out_fh, as they will interfere
144 with each other. 362 with each other.
145 363
364 Please note that "aio_sendfile" can read more bytes from $in_fh than
365 are written, and there is no way to find out how many bytes have
366 been read from "aio_sendfile" alone, as "aio_sendfile" only provides
367 the number of bytes written to $out_fh. Only if the result value
368 equals $length one can assume that $length bytes have been read.
369
370 Unlike with other "aio_" functions, it makes a lot of sense to use
371 "aio_sendfile" on non-blocking sockets, as long as one end
372 (typically the $in_fh) is a file - the file I/O will then be
373 asynchronous, while the socket I/O will be non-blocking. Note,
374 however, that you can run into a trap where "aio_sendfile" reads
375 some data with readahead, then fails to write all data, and when the
376 socket is ready the next time, the data in the cache is already
377 lost, forcing "aio_sendfile" to again hit the disk. Explicit
378 "aio_read" + "aio_write" let's you control resource usage much
379 better.
380
146 This call tries to make use of a native "sendfile" syscall to 381 This call tries to make use of a native "sendfile" syscall to
147 provide zero-copy operation. For this to work, $out_fh should refer 382 provide zero-copy operation. For this to work, $out_fh should refer
148 to a socket, and $in_fh should refer to mmap'able file. 383 to a socket, and $in_fh should refer to an mmap'able file.
149 384
150 If the native sendfile call fails or is not implemented, it will be 385 If a native sendfile cannot be found or it fails with "ENOSYS",
386 "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or "ENOTSOCK",
151 emulated, so you can call "aio_sendfile" on any type of filehandle 387 it will be emulated, so you can call "aio_sendfile" on any type of
152 regardless of the limitations of the operating system. 388 filehandle regardless of the limitations of the operating system.
153
154 Please note, however, that "aio_sendfile" can read more bytes from
155 $in_fh than are written, and there is no way to find out how many
156 bytes have been read from "aio_sendfile" alone, as "aio_sendfile"
157 only provides the number of bytes written to $out_fh. Only if the
158 result value equals $length one can assume that $length bytes have
159 been read.
160 389
161 aio_readahead $fh,$offset,$length, $callback->($retval) 390 aio_readahead $fh,$offset,$length, $callback->($retval)
162 "aio_readahead" populates the page cache with data from a file so 391 "aio_readahead" populates the page cache with data from a file so
163 that subsequent reads from that file will not block on disk I/O. The 392 that subsequent reads from that file will not block on disk I/O. The
164 $offset argument specifies the starting point from which data is to 393 $offset argument specifies the starting point from which data is to
… …
192 aio_stat "/etc/passwd", sub { 421 aio_stat "/etc/passwd", sub {
193 $_[0] and die "stat failed: $!"; 422 $_[0] and die "stat failed: $!";
194 print "size is ", -s _, "\n"; 423 print "size is ", -s _, "\n";
195 }; 424 };
196 425
426 aio_statvfs $fh_or_path, $callback->($statvfs)
427 Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
428 whether a file handle or path was passed.
429
430 On success, the callback is passed a hash reference with the
431 following members: "bsize", "frsize", "blocks", "bfree", "bavail",
432 "files", "ffree", "favail", "fsid", "flag" and "namemax". On
433 failure, "undef" is passed.
434
435 The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
436 and "ST_NOSUID".
437
438 The following non-POSIX IO::AIO::ST_* flag masks are defined to
439 their correct value when available, or to 0 on systems that do not
440 support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
441 "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
442 "ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
443
444 Example: stat "/wd" and dump out the data if successful.
445
446 aio_statvfs "/wd", sub {
447 my $f = $_[0]
448 or die "statvfs: $!";
449
450 use Data::Dumper;
451 say Dumper $f;
452 };
453
454 # result:
455 {
456 bsize => 1024,
457 bfree => 4333064312,
458 blocks => 10253828096,
459 files => 2050765568,
460 flag => 4096,
461 favail => 2042092649,
462 bavail => 4333064312,
463 ffree => 2042092649,
464 namemax => 255,
465 frsize => 1024,
466 fsid => 1810
467 }
468
469 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
470 Works like perl's "utime" function (including the special case of
471 $atime and $mtime being undef). Fractional times are supported if
472 the underlying syscalls support them.
473
474 When called with a pathname, uses utimes(2) if available, otherwise
475 utime(2). If called on a file descriptor, uses futimes(2) if
476 available, otherwise returns ENOSYS, so this is not portable.
477
478 Examples:
479
480 # set atime and mtime to current time (basically touch(1)):
481 aio_utime "path", undef, undef;
482 # set atime to current time and mtime to beginning of the epoch:
483 aio_utime "path", time, undef; # undef==0
484
485 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
486 Works like perl's "chown" function, except that "undef" for either
487 $uid or $gid is being interpreted as "do not change" (but -1 can
488 also be used).
489
490 Examples:
491
492 # same as "chown root path" in the shell:
493 aio_chown "path", 0, -1;
494 # same as above:
495 aio_chown "path", 0, undef;
496
497 aio_truncate $fh_or_path, $offset, $callback->($status)
498 Works like truncate(2) or ftruncate(2).
499
500 aio_chmod $fh_or_path, $mode, $callback->($status)
501 Works like perl's "chmod" function.
502
197 aio_unlink $pathname, $callback->($status) 503 aio_unlink $pathname, $callback->($status)
198 Asynchronously unlink (delete) a file and call the callback with the 504 Asynchronously unlink (delete) a file and call the callback with the
199 result code. 505 result code.
506
507 aio_mknod $path, $mode, $dev, $callback->($status)
508 [EXPERIMENTAL]
509
510 Asynchronously create a device node (or fifo). See mknod(2).
511
512 The only (POSIX-) portable way of calling this function is:
513
514 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
515
516 aio_link $srcpath, $dstpath, $callback->($status)
517 Asynchronously create a new link to the existing object at $srcpath
518 at the path $dstpath and call the callback with the result code.
519
520 aio_symlink $srcpath, $dstpath, $callback->($status)
521 Asynchronously create a new symbolic link to the existing object at
522 $srcpath at the path $dstpath and call the callback with the result
523 code.
524
525 aio_readlink $path, $callback->($link)
526 Asynchronously read the symlink specified by $path and pass it to
527 the callback. If an error occurs, nothing or undef gets passed to
528 the callback.
529
530 aio_rename $srcpath, $dstpath, $callback->($status)
531 Asynchronously rename the object at $srcpath to $dstpath, just as
532 rename(2) and call the callback with the result code.
533
534 aio_mkdir $pathname, $mode, $callback->($status)
535 Asynchronously mkdir (create) a directory and call the callback with
536 the result code. $mode will be modified by the umask at the time the
537 request is executed, so do not change your umask.
200 538
201 aio_rmdir $pathname, $callback->($status) 539 aio_rmdir $pathname, $callback->($status)
202 Asynchronously rmdir (delete) a directory and call the callback with 540 Asynchronously rmdir (delete) a directory and call the callback with
203 the result code. 541 the result code.
204 542
205 aio_readdir $pathname, $callback->($entries) 543 aio_readdir $pathname, $callback->($entries)
206 Unlike the POSIX call of the same name, "aio_readdir" reads an 544 Unlike the POSIX call of the same name, "aio_readdir" reads an
207 entire directory (i.e. opendir + readdir + closedir). The entries 545 entire directory (i.e. opendir + readdir + closedir). The entries
208 will not be sorted, and will NOT include the "." and ".." entries. 546 will not be sorted, and will NOT include the "." and ".." entries.
209 547
210 The callback a single argument which is either "undef" or an 548 The callback is passed a single argument which is either "undef" or
211 array-ref with the filenames. 549 an array-ref with the filenames.
550
551 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
552 Quite similar to "aio_readdir", but the $flags argument allows to
553 tune behaviour and output format. In case of an error, $entries will
554 be "undef".
555
556 The flags are a combination of the following constants, ORed
557 together (the flags will also be passed to the callback, possibly
558 modified):
559
560 IO::AIO::READDIR_DENTS
561 When this flag is off, then the callback gets an arrayref with
562 of names only (as with "aio_readdir"), otherwise it gets an
563 arrayref with "[$name, $type, $inode]" arrayrefs, each
564 describing a single directory entry in more detail.
565
566 $name is the name of the entry.
567
568 $type is one of the "IO::AIO::DT_xxx" constants:
569
570 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
571 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
572 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
573
574 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
575 you need to know, you have to run stat yourself. Also, for speed
576 reasons, the $type scalars are read-only: you can not modify
577 them.
578
579 $inode is the inode number (which might not be exact on systems
580 with 64 bit inode numbers and 32 bit perls). This field has
581 unspecified content on systems that do not deliver the inode
582 information.
583
584 IO::AIO::READDIR_DIRS_FIRST
585 When this flag is set, then the names will be returned in an
586 order where likely directories come first. This is useful when
587 you need to quickly find directories, or you want to find all
588 directories while avoiding to stat() each entry.
589
590 If the system returns type information in readdir, then this is
591 used to find directories directly. Otherwise, likely directories
592 are files beginning with ".", or otherwise files with no dots,
593 of which files with short names are tried first.
594
595 IO::AIO::READDIR_STAT_ORDER
596 When this flag is set, then the names will be returned in an
597 order suitable for stat()'ing each one. That is, when you plan
598 to stat() all files in the given directory, then the returned
599 order will likely be fastest.
600
601 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
602 specified, then the likely dirs come first, resulting in a less
603 optimal stat order.
604
605 IO::AIO::READDIR_FOUND_UNKNOWN
606 This flag should not be set when calling "aio_readdirx".
607 Instead, it is being set by "aio_readdirx", when any of the
608 $type's found were "IO::AIO::DT_UNKNOWN". The absense of this
609 flag therefore indicates that all $type's are known, which can
610 be used to speed up some algorithms.
611
612 aio_load $path, $data, $callback->($status)
613 This is a composite request that tries to fully load the given file
614 into memory. Status is the same as with aio_read.
615
616 aio_copy $srcpath, $dstpath, $callback->($status)
617 Try to copy the *file* (directories not supported as either source
618 or destination) from $srcpath to $dstpath and call the callback with
619 a status of 0 (ok) or -1 (error, see $!).
620
621 This is a composite request that creates the destination file with
622 mode 0200 and copies the contents of the source file into it using
623 "aio_sendfile", followed by restoring atime, mtime, access mode and
624 uid/gid, in that order.
625
626 If an error occurs, the partial destination file will be unlinked,
627 if possible, except when setting atime, mtime, access mode and
628 uid/gid, where errors are being ignored.
629
630 aio_move $srcpath, $dstpath, $callback->($status)
631 Try to move the *file* (directories not supported as either source
632 or destination) from $srcpath to $dstpath and call the callback with
633 a status of 0 (ok) or -1 (error, see $!).
634
635 This is a composite request that tries to rename(2) the file first;
636 if rename fails with "EXDEV", it copies the file with "aio_copy"
637 and, if that is successful, unlinks the $srcpath.
212 638
213 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 639 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
214 Scans a directory (similar to "aio_readdir") and tries to separate 640 Scans a directory (similar to "aio_readdir") but additionally tries
215 the entries of directory $path into two sets of names, ones you can 641 to efficiently separate the entries of directory $path into two sets
216 recurse into (directories), and ones you cannot recurse into 642 of names, directories you can recurse into (directories), and ones
217 (everything else). 643 you cannot recurse into (everything else, including symlinks to
644 directories).
218 645
219 "aio_scandir" is a composite request that consists of many 646 "aio_scandir" is a composite request that creates of many sub
220 aio-primitives. $maxreq specifies the maximum number of outstanding 647 requests_ $maxreq specifies the maximum number of outstanding aio
221 aio requests that this function generates. If it is "<= 0", then a 648 requests that this function generates. If it is "<= 0", then a
222 suitable default will be chosen (currently 8). 649 suitable default will be chosen (currently 4).
223 650
224 On error, the callback is called without arguments, otherwise it 651 On error, the callback is called without arguments, otherwise it
225 receives two array-refs with path-relative entry names. 652 receives two array-refs with path-relative entry names.
226 653
227 Example: 654 Example:
… …
235 Implementation notes. 662 Implementation notes.
236 663
237 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry 664 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
238 can. 665 can.
239 666
667 If readdir returns file type information, then this is used directly
668 to find directories.
669
240 After reading the directory, the modification time, size etc. of the 670 Otherwise, after reading the directory, the modification time, size
241 directory before and after the readdir is checked, and if they 671 etc. of the directory before and after the readdir is checked, and
242 match, the link count will be used to decide how many entries are 672 if they match (and isn't the current time), the link count will be
243 directories (if >= 2). Otherwise, no knowledge of the number of 673 used to decide how many entries are directories (if >= 2).
244 subdirectories will be assumed. 674 Otherwise, no knowledge of the number of subdirectories will be
675 assumed.
245 676
246 Then entires will be sorted into likely directories (everything 677 Then entries will be sorted into likely directories a non-initial
247 without a non-initial dot) and likely non-directories (everything 678 dot currently) and likely non-directories (see "aio_readdirx"). Then
248 else). Then every entry + "/." will be "stat"'ed, likely directories 679 every entry plus an appended "/." will be "stat"'ed, likely
249 first. This is often faster because filesystems might detect the 680 directories first, in order of their inode numbers. If that
681 succeeds, it assumes that the entry is a directory or a symlink to
682 directory (which will be checked seperately). This is often faster
683 than stat'ing the entry itself because filesystems might detect the
250 type of the entry without reading the inode data (e.g. ext2s 684 type of the entry without reading the inode data (e.g. ext2fs
251 filetype feature). If that succeeds, it assumes that the entry is a 685 filetype feature), even on systems that cannot return the filetype
252 directory or a symlink to directory (which will be checked 686 information on readdir.
253 seperately).
254 687
255 If the known number of directories has been reached, the rest of the 688 If the known number of directories (link count - 2) has been
256 entries is assumed to be non-directories. 689 reached, the rest of the entries is assumed to be non-directories.
690
691 This only works with certainty on POSIX (= UNIX) filesystems, which
692 fortunately are the vast majority of filesystems around.
693
694 It will also likely work on non-POSIX filesystems with reduced
695 efficiency as those tend to return 0 or 1 as link counts, which
696 disables the directory counting heuristic.
697
698 aio_rmtree $path, $callback->($status)
699 Delete a directory tree starting (and including) $path, return the
700 status of the final "rmdir" only. This is a composite request that
701 uses "aio_scandir" to recurse into and rmdir directories, and unlink
702 everything else.
703
704 aio_sync $callback->($status)
705 Asynchronously call sync and call the callback when finished.
257 706
258 aio_fsync $fh, $callback->($status) 707 aio_fsync $fh, $callback->($status)
259 Asynchronously call fsync on the given filehandle and call the 708 Asynchronously call fsync on the given filehandle and call the
260 callback with the fsync result code. 709 callback with the fsync result code.
261 710
… …
264 callback with the fdatasync result code. 713 callback with the fdatasync result code.
265 714
266 If this call isn't available because your OS lacks it or it couldn't 715 If this call isn't available because your OS lacks it or it couldn't
267 be detected, it will be emulated by calling "fsync" instead. 716 be detected, it will be emulated by calling "fsync" instead.
268 717
718 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
719 Sync the data portion of the file specified by $offset and $length
720 to disk (but NOT the metadata), by calling the Linux-specific
721 sync_file_range call. If sync_file_range is not available or it
722 returns ENOSYS, then fdatasync or fsync is being substituted.
723
724 $flags can be a combination of
725 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
726 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
727 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
728 manpage for details.
729
730 aio_pathsync $path, $callback->($status)
731 This request tries to open, fsync and close the given path. This is
732 a composite request intended to sync directories after directory
733 operations (E.g. rename). This might not work on all operating
734 systems or have any specific effect, but usually it makes sure that
735 directory changes get written to disc. It works for anything that
736 can be opened for read-only, not just directories.
737
738 Future versions of this function might fall back to other methods
739 when "fsync" on the directory fails (such as calling "sync").
740
741 Passes 0 when everything went ok, and -1 on error.
742
743 aio_msync $scalar, $offset = 0, $length = undef, flags = 0,
744 $callback->($status)
745 This is a rather advanced IO::AIO call, which only works on
746 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
747 also works on data scalars managed by the Sys::Mmap or Mmap modules,
748 note that the scalar must only be modified in-place while an aio
749 operation is pending on it).
750
751 It calls the "msync" function of your OS, if available, with the
752 memory area starting at $offset in the string and ending $length
753 bytes later. If $length is negative, counts from the end, and if
754 $length is "undef", then it goes till the end of the string. The
755 flags can be a combination of "IO::AIO::MS_ASYNC",
756 "IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC".
757
758 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
759 $callback->($status)
760 This is a rather advanced IO::AIO call, which works best on
761 mmap(2)ed scalars.
762
763 It touches (reads or writes) all memory pages in the specified range
764 inside the scalar. All caveats and parameters are the same as for
765 "aio_msync", above, except for flags, which must be either 0 (which
766 reads all pages and ensures they are instantiated) or
767 "IO::AIO::MT_MODIFY", which modifies the memory page s(by reading
768 and writing an octet from it, which dirties the page).
769
770 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
771 This is a rather advanced IO::AIO call, which works best on
772 mmap(2)ed scalars.
773
774 It reads in all the pages of the underlying storage into memory (if
775 any) and locks them, so they are not getting swapped/paged out or
776 removed.
777
778 If $length is undefined, then the scalar will be locked till the
779 end.
780
781 On systems that do not implement "mlock", this function returns -1
782 and sets errno to "ENOSYS".
783
784 Note that the corresponding "munlock" is synchronous and is
785 documented under "MISCELLANEOUS FUNCTIONS".
786
787 Example: open a file, mmap and mlock it - both will be undone when
788 $data gets destroyed.
789
790 open my $fh, "<", $path or die "$path: $!";
791 my $data;
792 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
793 aio_mlock $data; # mlock in background
794
795 aio_mlockall $flags, $callback->($status)
796 Calls the "mlockall" function with the given $flags (a combination
797 of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
798
799 On systems that do not implement "mlockall", this function returns
800 -1 and sets errno to "ENOSYS".
801
802 Note that the corresponding "munlockall" is synchronous and is
803 documented under "MISCELLANEOUS FUNCTIONS".
804
805 Example: asynchronously lock all current and future pages into
806 memory.
807
808 aio_mlockall IO::AIO::MCL_FUTURE;
809
810 aio_group $callback->(...)
811 This is a very special aio request: Instead of doing something, it
812 is a container for other aio requests, which is useful if you want
813 to bundle many requests into a single, composite, request with a
814 definite callback and the ability to cancel the whole request with
815 its subrequests.
816
817 Returns an object of class IO::AIO::GRP. See its documentation below
818 for more info.
819
820 Example:
821
822 my $grp = aio_group sub {
823 print "all stats done\n";
824 };
825
826 add $grp
827 (aio_stat ...),
828 (aio_stat ...),
829 ...;
830
831 aio_nop $callback->()
832 This is a special request - it does nothing in itself and is only
833 used for side effects, such as when you want to add a dummy request
834 to a group so that finishing the requests in the group depends on
835 executing the given code.
836
837 While this request does nothing, it still goes through the execution
838 phase and still requires a worker thread. Thus, the callback will
839 not be executed immediately but only after other requests in the
840 queue have entered their execution phase. This can be used to
841 measure request latency.
842
843 IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
844 Mainly used for debugging and benchmarking, this aio request puts
845 one of the request workers to sleep for the given time.
846
847 While it is theoretically handy to have simple I/O scheduling
848 requests like sleep and file handle readable/writable, the overhead
849 this creates is immense (it blocks a thread for a long time) so do
850 not use this function except to put your application under
851 artificial I/O pressure.
852
853 IO::AIO::REQ CLASS
854 All non-aggregate "aio_*" functions return an object of this class when
855 called in non-void context.
856
857 cancel $req
858 Cancels the request, if possible. Has the effect of skipping
859 execution when entering the execute state and skipping calling the
860 callback when entering the the result state, but will leave the
861 request otherwise untouched (with the exception of readdir). That
862 means that requests that currently execute will not be stopped and
863 resources held by the request will not be freed prematurely.
864
865 cb $req $callback->(...)
866 Replace (or simply set) the callback registered to the request.
867
868 IO::AIO::GRP CLASS
869 This class is a subclass of IO::AIO::REQ, so all its methods apply to
870 objects of this class, too.
871
872 A IO::AIO::GRP object is a special request that can contain multiple
873 other aio requests.
874
875 You create one by calling the "aio_group" constructing function with a
876 callback that will be called when all contained requests have entered
877 the "done" state:
878
879 my $grp = aio_group sub {
880 print "all requests are done\n";
881 };
882
883 You add requests by calling the "add" method with one or more
884 "IO::AIO::REQ" objects:
885
886 $grp->add (aio_unlink "...");
887
888 add $grp aio_stat "...", sub {
889 $_[0] or return $grp->result ("error");
890
891 # add another request dynamically, if first succeeded
892 add $grp aio_open "...", sub {
893 $grp->result ("ok");
894 };
895 };
896
897 This makes it very easy to create composite requests (see the source of
898 "aio_move" for an application) that work and feel like simple requests.
899
900 * The IO::AIO::GRP objects will be cleaned up during calls to
901 "IO::AIO::poll_cb", just like any other request.
902
903 * They can be canceled like any other request. Canceling will cancel
904 not only the request itself, but also all requests it contains.
905
906 * They can also can also be added to other IO::AIO::GRP objects.
907
908 * You must not add requests to a group from within the group callback
909 (or any later time).
910
911 Their lifetime, simplified, looks like this: when they are empty, they
912 will finish very quickly. If they contain only requests that are in the
913 "done" state, they will also finish. Otherwise they will continue to
914 exist.
915
916 That means after creating a group you have some time to add requests
917 (precisely before the callback has been invoked, which is only done
918 within the "poll_cb"). And in the callbacks of those requests, you can
919 add further requests to the group. And only when all those requests have
920 finished will the the group itself finish.
921
922 add $grp ...
923 $grp->add (...)
924 Add one or more requests to the group. Any type of IO::AIO::REQ can
925 be added, including other groups, as long as you do not create
926 circular dependencies.
927
928 Returns all its arguments.
929
930 $grp->cancel_subs
931 Cancel all subrequests and clears any feeder, but not the group
932 request itself. Useful when you queued a lot of events but got a
933 result early.
934
935 The group request will finish normally (you cannot add requests to
936 the group).
937
938 $grp->result (...)
939 Set the result value(s) that will be passed to the group callback
940 when all subrequests have finished and set the groups errno to the
941 current value of errno (just like calling "errno" without an error
942 number). By default, no argument will be passed and errno is zero.
943
944 $grp->errno ([$errno])
945 Sets the group errno value to $errno, or the current value of errno
946 when the argument is missing.
947
948 Every aio request has an associated errno value that is restored
949 when the callback is invoked. This method lets you change this value
950 from its default (0).
951
952 Calling "result" will also set errno, so make sure you either set $!
953 before the call to "result", or call c<errno> after it.
954
955 feed $grp $callback->($grp)
956 Sets a feeder/generator on this group: every group can have an
957 attached generator that generates requests if idle. The idea behind
958 this is that, although you could just queue as many requests as you
959 want in a group, this might starve other requests for a potentially
960 long time. For example, "aio_scandir" might generate hundreds of
961 thousands "aio_stat" requests, delaying any later requests for a
962 long time.
963
964 To avoid this, and allow incremental generation of requests, you can
965 instead a group and set a feeder on it that generates those
966 requests. The feed callback will be called whenever there are few
967 enough (see "limit", below) requests active in the group itself and
968 is expected to queue more requests.
969
970 The feed callback can queue as many requests as it likes (i.e. "add"
971 does not impose any limits).
972
973 If the feed does not queue more requests when called, it will be
974 automatically removed from the group.
975
976 If the feed limit is 0 when this method is called, it will be set to
977 2 automatically.
978
979 Example:
980
981 # stat all files in @files, but only ever use four aio requests concurrently:
982
983 my $grp = aio_group sub { print "finished\n" };
984 limit $grp 4;
985 feed $grp sub {
986 my $file = pop @files
987 or return;
988
989 add $grp aio_stat $file, sub { ... };
990 };
991
992 limit $grp $num
993 Sets the feeder limit for the group: The feeder will be called
994 whenever the group contains less than this many requests.
995
996 Setting the limit to 0 will pause the feeding process.
997
998 The default value for the limit is 0, but note that setting a feeder
999 automatically bumps it up to 2.
1000
269 SUPPORT FUNCTIONS 1001 SUPPORT FUNCTIONS
1002 EVENT PROCESSING AND EVENT LOOP INTEGRATION
270 $fileno = IO::AIO::poll_fileno 1003 $fileno = IO::AIO::poll_fileno
271 Return the *request result pipe file descriptor*. This filehandle 1004 Return the *request result pipe file descriptor*. This filehandle
272 must be polled for reading by some mechanism outside this module 1005 must be polled for reading by some mechanism outside this module
273 (e.g. Event or select, see below or the SYNOPSIS). If the pipe 1006 (e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
274 becomes readable you have to call "poll_cb" to check the results. 1007 pipe becomes readable you have to call "poll_cb" to check the
1008 results.
275 1009
276 See "poll_cb" for an example. 1010 See "poll_cb" for an example.
277 1011
278 IO::AIO::poll_cb 1012 IO::AIO::poll_cb
279 Process all outstanding events on the result pipe. You have to call 1013 Process some outstanding events on the result pipe. You have to call
280 this regularly. Returns the number of events processed. Returns 1014 this regularly. Returns 0 if all events could be processed, or -1 if
281 immediately when no events are outstanding. 1015 it returned earlier for whatever reason. Returns immediately when no
1016 events are outstanding. The amount of events processed depends on
1017 the settings of "IO::AIO::max_poll_req" and
1018 "IO::AIO::max_poll_time".
1019
1020 If not all requests were processed for whatever reason, the
1021 filehandle will still be ready when "poll_cb" returns, so normally
1022 you don't have to do anything special to have it called later.
282 1023
283 Example: Install an Event watcher that automatically calls 1024 Example: Install an Event watcher that automatically calls
284 IO::AIO::poll_cb with high priority: 1025 IO::AIO::poll_cb with high priority (more examples can be found in
1026 the SYNOPSIS section, at the top of this document):
285 1027
286 Event->io (fd => IO::AIO::poll_fileno, 1028 Event->io (fd => IO::AIO::poll_fileno,
287 poll => 'r', async => 1, 1029 poll => 'r', async => 1,
288 cb => \&IO::AIO::poll_cb); 1030 cb => \&IO::AIO::poll_cb);
289 1031
290 IO::AIO::poll_wait 1032 IO::AIO::poll_wait
1033 If there are any outstanding requests and none of them in the result
291 Wait till the result filehandle becomes ready for reading (simply 1034 phase, wait till the result filehandle becomes ready for reading
292 does a "select" on the filehandle. This is useful if you want to 1035 (simply does a "select" on the filehandle. This is useful if you
293 synchronously wait for some requests to finish). 1036 want to synchronously wait for some requests to finish).
294 1037
295 See "nreqs" for an example. 1038 See "nreqs" for an example.
296 1039
1040 IO::AIO::poll
1041 Waits until some requests have been handled.
1042
1043 Returns the number of requests processed, but is otherwise strictly
1044 equivalent to:
1045
1046 IO::AIO::poll_wait, IO::AIO::poll_cb
1047
297 IO::AIO::nreqs 1048 IO::AIO::flush
298 Returns the number of requests currently outstanding (i.e. for which 1049 Wait till all outstanding AIO requests have been handled.
299 their callback has not been invoked yet).
300 1050
301 Example: wait till there are no outstanding requests anymore: 1051 Strictly equivalent to:
302 1052
303 IO::AIO::poll_wait, IO::AIO::poll_cb 1053 IO::AIO::poll_wait, IO::AIO::poll_cb
304 while IO::AIO::nreqs; 1054 while IO::AIO::nreqs;
305 1055
306 IO::AIO::flush 1056 IO::AIO::max_poll_reqs $nreqs
307 Wait till all outstanding AIO requests have been handled. 1057 IO::AIO::max_poll_time $seconds
1058 These set the maximum number of requests (default 0, meaning
1059 infinity) that are being processed by "IO::AIO::poll_cb" in one
1060 call, respectively the maximum amount of time (default 0, meaning
1061 infinity) spent in "IO::AIO::poll_cb" to process requests (more
1062 correctly the mininum amount of time "poll_cb" is allowed to use).
308 1063
309 Strictly equivalent to: 1064 Setting "max_poll_time" to a non-zero value creates an overhead of
1065 one syscall per request processed, which is not normally a problem
1066 unless your callbacks are really really fast or your OS is really
1067 really slow (I am not mentioning Solaris here). Using
1068 "max_poll_reqs" incurs no overhead.
310 1069
311 IO::AIO::poll_wait, IO::AIO::poll_cb 1070 Setting these is useful if you want to ensure some level of
312 while IO::AIO::nreqs; 1071 interactiveness when perl is not fast enough to process all requests
1072 in time.
313 1073
314 IO::AIO::poll 1074 For interactive programs, values such as 0.01 to 0.1 should be fine.
315 Waits until some requests have been handled.
316 1075
317 Strictly equivalent to: 1076 Example: Install an Event watcher that automatically calls
1077 IO::AIO::poll_cb with low priority, to ensure that other parts of
1078 the program get the CPU sometimes even under high AIO load.
318 1079
319 IO::AIO::poll_wait, IO::AIO::poll_cb 1080 # try not to spend much more than 0.1s in poll_cb
320 if IO::AIO::nreqs; 1081 IO::AIO::max_poll_time 0.1;
321 1082
1083 # use a low priority so other tasks have priority
1084 Event->io (fd => IO::AIO::poll_fileno,
1085 poll => 'r', nice => 1,
1086 cb => &IO::AIO::poll_cb);
1087
1088 CONTROLLING THE NUMBER OF THREADS
322 IO::AIO::min_parallel $nthreads 1089 IO::AIO::min_parallel $nthreads
323 Set the minimum number of AIO threads to $nthreads. The current 1090 Set the minimum number of AIO threads to $nthreads. The current
324 default is 4, which means four asynchronous operations can be done 1091 default is 8, which means eight asynchronous operations can execute
325 at one time (the number of outstanding operations, however, is 1092 concurrently at any one time (the number of outstanding requests,
326 unlimited). 1093 however, is unlimited).
327 1094
328 IO::AIO starts threads only on demand, when an AIO request is queued 1095 IO::AIO starts threads only on demand, when an AIO request is queued
329 and no free thread exists. 1096 and no free thread exists. Please note that queueing up a hundred
1097 requests can create demand for a hundred threads, even if it turns
1098 out that everything is in the cache and could have been processed
1099 faster by a single thread.
330 1100
331 It is recommended to keep the number of threads low, as some Linux 1101 It is recommended to keep the number of threads relatively low, as
332 kernel versions will scale negatively with the number of threads 1102 some Linux kernel versions will scale negatively with the number of
333 (higher parallelity => MUCH higher latency). With current Linux 2.6 1103 threads (higher parallelity => MUCH higher latency). With current
334 versions, 4-32 threads should be fine. 1104 Linux 2.6 versions, 4-32 threads should be fine.
335 1105
336 Under most circumstances you don't need to call this function, as 1106 Under most circumstances you don't need to call this function, as
337 the module selects a default that is suitable for low to moderate 1107 the module selects a default that is suitable for low to moderate
338 load. 1108 load.
339 1109
… …
349 ensure that all threads are killed and that there are no outstanding 1119 ensure that all threads are killed and that there are no outstanding
350 requests. 1120 requests.
351 1121
352 Under normal circumstances you don't need to call this function. 1122 Under normal circumstances you don't need to call this function.
353 1123
1124 IO::AIO::max_idle $nthreads
1125 Limit the number of threads (default: 4) that are allowed to idle
1126 (i.e., threads that did not get a request to process within 10
1127 seconds). That means if a thread becomes idle while $nthreads other
1128 threads are also idle, it will free its resources and exit.
1129
1130 This is useful when you allow a large number of threads (e.g. 100 or
1131 1000) to allow for extremely high load situations, but want to free
1132 resources under normal circumstances (1000 threads can easily
1133 consume 30MB of RAM).
1134
1135 The default is probably ok in most situations, especially if thread
1136 creation is fast. If thread creation is very slow on your system you
1137 might want to use larger values.
1138
354 $oldnreqs = IO::AIO::max_outstanding $nreqs 1139 IO::AIO::max_outstanding $maxreqs
1140 This is a very bad function to use in interactive programs because
1141 it blocks, and a bad way to reduce concurrency because it is
1142 inexact: Better use an "aio_group" together with a feed callback.
1143
355 Sets the maximum number of outstanding requests to $nreqs. If you 1144 Sets the maximum number of outstanding requests to $nreqs. If you do
356 try to queue up more than this number of requests, the caller will 1145 queue up more than this number of requests, the next call to the
357 block until some requests have been handled. 1146 "poll_cb" (and "poll_some" and other functions calling "poll_cb")
1147 function will block until the limit is no longer exceeded.
358 1148
359 The default is very large, so normally there is no practical limit. 1149 The default value is very large, so there is no practical limit on
360 If you queue up many requests in a loop it often improves speed if 1150 the number of outstanding requests.
361 you set this to a relatively low number, such as 100.
362 1151
363 Under normal circumstances you don't need to call this function. 1152 You can still queue as many requests as you want. Therefore,
1153 "max_outstanding" is mainly useful in simple scripts (with low
1154 values) or as a stop gap to shield against fatal memory overflow
1155 (with large values).
1156
1157 STATISTICAL INFORMATION
1158 IO::AIO::nreqs
1159 Returns the number of requests currently in the ready, execute or
1160 pending states (i.e. for which their callback has not been invoked
1161 yet).
1162
1163 Example: wait till there are no outstanding requests anymore:
1164
1165 IO::AIO::poll_wait, IO::AIO::poll_cb
1166 while IO::AIO::nreqs;
1167
1168 IO::AIO::nready
1169 Returns the number of requests currently in the ready state (not yet
1170 executed).
1171
1172 IO::AIO::npending
1173 Returns the number of requests currently in the pending state
1174 (executed, but not yet processed by poll_cb).
1175
1176 MISCELLANEOUS FUNCTIONS
1177 IO::AIO implements some functions that might be useful, but are not
1178 asynchronous.
1179
1180 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1181 Calls the "eio_sendfile_sync" function, which is like
1182 "aio_sendfile", but is blocking (this makes most sense if you know
1183 the input data is likely cached already and the output filehandle is
1184 set to non-blocking operations).
1185
1186 Returns the number of bytes copied, or -1 on error.
1187
1188 IO::AIO::fadvise $fh, $offset, $len, $advice
1189 Simply calls the "posix_fadvise" function (see its manpage for
1190 details). The following advice constants are avaiable:
1191 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1192 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1193 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1194
1195 On systems that do not implement "posix_fadvise", this function
1196 returns ENOSYS, otherwise the return value of "posix_fadvise".
1197
1198 IO::AIO::madvise $scalar, $offset, $len, $advice
1199 Simply calls the "posix_madvise" function (see its manpage for
1200 details). The following advice constants are avaiable:
1201 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1202 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1203 "IO::AIO::MADV_DONTNEED".
1204
1205 On systems that do not implement "posix_madvise", this function
1206 returns ENOSYS, otherwise the return value of "posix_madvise".
1207
1208 IO::AIO::mprotect $scalar, $offset, $len, $protect
1209 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1210 $scalar (see its manpage for details). The following protect
1211 constants are avaiable: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1212 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1213
1214 On systems that do not implement "mprotect", this function returns
1215 ENOSYS, otherwise the return value of "mprotect".
1216
1217 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1218 Memory-maps a file (or anonymous memory range) and attaches it to
1219 the given $scalar, which will act like a string scalar.
1220
1221 The only operations allowed on the scalar are "substr"/"vec" that
1222 don't change the string length, and most read-only operations such
1223 as copying it or searching it with regexes and so on.
1224
1225 Anything else is unsafe and will, at best, result in memory leaks.
1226
1227 The memory map associated with the $scalar is automatically removed
1228 when the $scalar is destroyed, or when the "IO::AIO::mmap" or
1229 "IO::AIO::munmap" functions are called.
1230
1231 This calls the "mmap"(2) function internally. See your system's
1232 manual page for details on the $length, $prot and $flags parameters.
1233
1234 The $length must be larger than zero and smaller than the actual
1235 filesize.
1236
1237 $prot is a combination of "IO::AIO::PROT_NONE",
1238 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1239 "IO::AIO::PROT_WRITE",
1240
1241 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1242 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1243 not available, the are defined as 0): "IO::AIO::MAP_ANONYMOUS"
1244 (which is set to "MAP_ANON" if your system only provides this
1245 constant), "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED",
1246 "IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or
1247 "IO::AIO::MAP_NONBLOCK"
1248
1249 If $fh is "undef", then a file descriptor of -1 is passed.
1250
1251 $offset is the offset from the start of the file - it generally must
1252 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
1253
1254 Example:
1255
1256 use Digest::MD5;
1257 use IO::AIO;
1258
1259 open my $fh, "<verybigfile"
1260 or die "$!";
1261
1262 IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
1263 or die "verybigfile: $!";
1264
1265 my $fast_md5 = md5 $data;
1266
1267 IO::AIO::munmap $scalar
1268 Removes a previous mmap and undefines the $scalar.
1269
1270 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1271 Calls the "munlock" function, undoing the effects of a previous
1272 "aio_mlock" call (see its description for details).
1273
1274 IO::AIO::munlockall
1275 Calls the "munlockall" function.
1276
1277 On systems that do not implement "munlockall", this function returns
1278 ENOSYS, otherwise the return value of "munlockall".
1279
1280EVENT LOOP INTEGRATION
1281 It is recommended to use AnyEvent::AIO to integrate IO::AIO
1282 automatically into many event loops:
1283
1284 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
1285 use AnyEvent::AIO;
1286
1287 You can also integrate IO::AIO manually into many event loops, here are
1288 some examples of how to do this:
1289
1290 # EV integration
1291 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
1292
1293 # Event integration
1294 Event->io (fd => IO::AIO::poll_fileno,
1295 poll => 'r',
1296 cb => \&IO::AIO::poll_cb);
1297
1298 # Glib/Gtk2 integration
1299 add_watch Glib::IO IO::AIO::poll_fileno,
1300 in => sub { IO::AIO::poll_cb; 1 };
1301
1302 # Tk integration
1303 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
1304 readable => \&IO::AIO::poll_cb);
1305
1306 # Danga::Socket integration
1307 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1308 \&IO::AIO::poll_cb);
364 1309
365 FORK BEHAVIOUR 1310 FORK BEHAVIOUR
1311 This module should do "the right thing" when the process using it forks:
1312
366 Before the fork, IO::AIO enters a quiescent state where no requests can 1313 Before the fork, IO::AIO enters a quiescent state where no requests can
367 be added in other threads and no results will be processed. After the 1314 be added in other threads and no results will be processed. After the
368 fork the parent simply leaves the quiescent state and continues 1315 fork the parent simply leaves the quiescent state and continues
369 request/result processing, while the child clears the request/result 1316 request/result processing, while the child frees the request/result
370 queue (so the requests started before the fork will only be handled in 1317 queue (so that the requests started before the fork will only be handled
371 the parent). Threats will be started on demand until the limit ste in 1318 in the parent). Threads will be started on demand until the limit set in
372 the parent process has been reached again. 1319 the parent process has been reached again.
373 1320
1321 In short: the parent will, after a short pause, continue as if fork had
1322 not been called, while the child will act as if IO::AIO has not been
1323 used yet.
1324
1325 MEMORY USAGE
1326 Per-request usage:
1327
1328 Each aio request uses - depending on your architecture - around 100-200
1329 bytes of memory. In addition, stat requests need a stat buffer (possibly
1330 a few hundred bytes), readdir requires a result buffer and so on. Perl
1331 scalars and other data passed into aio requests will also be locked and
1332 will consume memory till the request has entered the done state.
1333
1334 This is not awfully much, so queuing lots of requests is not usually a
1335 problem.
1336
1337 Per-thread usage:
1338
1339 In the execution phase, some aio requests require more memory for
1340 temporary buffers, and each thread requires a stack and other data
1341 structures (usually around 16k-128k, depending on the OS).
1342
1343KNOWN BUGS
1344 Known bugs will be fixed in the next release.
1345
374SEE ALSO 1346SEE ALSO
375 Coro, Linux::AIO. 1347 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
1348 more natural syntax.
376 1349
377AUTHOR 1350AUTHOR
378 Marc Lehmann <schmorp@schmorp.de> 1351 Marc Lehmann <schmorp@schmorp.de>
379 http://home.schmorp.de/ 1352 http://home.schmorp.de/
380 1353

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