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Revision 1.9 by root, Tue Aug 16 23:33:38 2005 UTC

1NAME 1NAME
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
7 aio_open "/etc/passwd", O_RDONLY, 0, sub {
8 my ($fh) = @_;
9 ...
10 };
11
12 aio_unlink "/tmp/file", sub { };
13
14 aio_read $fh, 30000, 1024, $buffer, 0, sub {
15 $_[0] > 0 or die "read error: $!";
16 };
17
18 # Event
19 Event->io (fd => IO::AIO::poll_fileno,
20 poll => 'r',
21 cb => \&IO::AIO::poll_cb);
22
23 # Glib/Gtk2
24 add_watch Glib::IO IO::AIO::poll_fileno,
25 in => sub { IO::AIO::poll_cb; 1 };
26
27 # Tk
28 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
29 readable => \&IO::AIO::poll_cb);
30
31 # Danga::Socket
32 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
33 \&IO::AIO::poll_cb);
6 34
7DESCRIPTION 35DESCRIPTION
8 This module implements asynchronous I/O using whatever means your 36 This module implements asynchronous I/O using whatever means your
9 operating system supports. 37 operating system supports.
10 38
… …
17 currently, for example), and they would only support aio_read and 45 currently, for example), and they would only support aio_read and
18 aio_write, so the remaining functionality would have to be implemented 46 aio_write, so the remaining functionality would have to be implemented
19 using threads anyway. 47 using threads anyway.
20 48
21 Although the module will work with in the presence of other threads, it 49 Although the module will work with in the presence of other threads, it
22 is currently not reentrant, so use appropriate locking yourself. 50 is currently not reentrant, so use appropriate locking yourself, always
51 call "poll_cb" from within the same thread, or never call "poll_cb" (or
52 other "aio_" functions) recursively.
23 53
24FUNCTIONS 54FUNCTIONS
25 AIO FUNCTIONS 55 AIO FUNCTIONS
26 All the "aio_*" calls are more or less thin wrappers around the syscall 56 All the "aio_*" calls are more or less thin wrappers around the syscall
27 with the same name (sans "aio_"). The arguments are similar or 57 with the same name (sans "aio_"). The arguments are similar or
28 identical, and they all accept an additional $callback argument which 58 identical, and they all accept an additional (and optional) $callback
29 must be a code reference. This code reference will get called with the 59 argument which must be a code reference. This code reference will get
30 syscall return code (e.g. most syscalls return -1 on error, unlike perl, 60 called with the syscall return code (e.g. most syscalls return -1 on
31 which usually delivers "false") as it's sole argument when the given 61 error, unlike perl, which usually delivers "false") as it's sole
32 syscall has been executed asynchronously. 62 argument when the given syscall has been executed asynchronously.
33 63
34 All functions that expect a filehandle will also accept a file 64 All functions expecting a filehandle keep a copy of the filehandle
35 descriptor. 65 internally until the request has finished.
36 66
37 The filenames you pass to these routines *must* be absolute. The reason 67 The pathnames you pass to these routines *must* be absolute and encoded
38 is that at the time the request is being executed, the current working 68 in byte form. The reason for the former is that at the time the request
39 directory could have changed. Alternatively, you can make sure that you 69 is being executed, the current working directory could have changed.
40 never change the current working directory. 70 Alternatively, you can make sure that you never change the current
71 working directory.
72
73 To encode pathnames to byte form, either make sure you either: a) always
74 pass in filenames you got from outside (command line, readdir etc.), b)
75 are ASCII or ISO 8859-1, c) use the Encode module and encode your
76 pathnames to the locale (or other) encoding in effect in the user
77 environment, d) use Glib::filename_from_unicode on unicode filenames or
78 e) use something else.
41 79
42 aio_open $pathname, $flags, $mode, $callback 80 aio_open $pathname, $flags, $mode, $callback
43 Asynchronously open or create a file and call the callback with a 81 Asynchronously open or create a file and call the callback with a
44 newly created filehandle for the file. 82 newly created filehandle for the file.
45 83
46 The pathname passed to "aio_open" must be absolute. See API NOTES, 84 The pathname passed to "aio_open" must be absolute. See API NOTES,
47 above, for an explanation. 85 above, for an explanation.
48 86
49 The $mode argument is a bitmask. See the "Fcntl" module for a list. 87 The $flags argument is a bitmask. See the "Fcntl" module for a list.
50 They are the same as used in "sysopen". 88 They are the same as used by "sysopen".
89
90 Likewise, $mode specifies the mode of the newly created file, if it
91 didn't exist and "O_CREAT" has been given, just like perl's
92 "sysopen", except that it is mandatory (i.e. use 0 if you don't
93 create new files, and 0666 or 0777 if you do).
51 94
52 Example: 95 Example:
53 96
54 aio_open "/etc/passwd", O_RDONLY, 0, sub { 97 aio_open "/etc/passwd", O_RDONLY, 0, sub {
55 if ($_[0]) { 98 if ($_[0]) {
… …
62 105
63 aio_close $fh, $callback 106 aio_close $fh, $callback
64 Asynchronously close a file and call the callback with the result 107 Asynchronously close a file and call the callback with the result
65 code. *WARNING:* although accepted, you should not pass in a perl 108 code. *WARNING:* although accepted, you should not pass in a perl
66 filehandle here, as perl will likely close the file descriptor 109 filehandle here, as perl will likely close the file descriptor
67 itself when the filehandle is destroyed. Normally, you can safely 110 another time when the filehandle is destroyed. Normally, you can
68 call perls "close" or just let filehandles go out of scope. 111 safely call perls "close" or just let filehandles go out of scope.
112
113 This is supposed to be a bug in the API, so that might change. It's
114 therefore best to avoid this function.
69 115
70 aio_read $fh,$offset,$length, $data,$dataoffset,$callback 116 aio_read $fh,$offset,$length, $data,$dataoffset,$callback
71 aio_write $fh,$offset,$length, $data,$dataoffset,$callback 117 aio_write $fh,$offset,$length, $data,$dataoffset,$callback
72 Reads or writes "length" bytes from the specified "fh" and "offset" 118 Reads or writes "length" bytes from the specified "fh" and "offset"
73 into the scalar given by "data" and offset "dataoffset" and calls 119 into the scalar given by "data" and offset "dataoffset" and calls
74 the callback without the actual number of bytes read (or -1 on 120 the callback without the actual number of bytes read (or -1 on
75 error, just like the syscall). 121 error, just like the syscall).
76 122
77 Example: Read 15 bytes at offset 7 into scalar $buffer, strating at 123 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
78 offset 0 within the scalar: 124 offset 0 within the scalar:
79 125
80 aio_read $fh, 7, 15, $buffer, 0, sub { 126 aio_read $fh, 7, 15, $buffer, 0, sub {
81 $_[0] >= 0 or die "read error: $!"; 127 $_[0] > 0 or die "read error: $!";
82 print "read <$buffer>\n"; 128 print "read $_[0] bytes: <$buffer>\n";
83 }; 129 };
84 130
85 aio_readahead $fh,$offset,$length, $callback 131 aio_readahead $fh,$offset,$length, $callback
86 Asynchronously reads the specified byte range into the page cache,
87 using the "readahead" syscall. If that syscall doesn't exist the
88 status will be -1 and $! is set to ENOSYS.
89
90 readahead() populates the page cache with data from a file so that 132 "aio_readahead" populates the page cache with data from a file so
91 subsequent reads from that file will not block on disk I/O. The 133 that subsequent reads from that file will not block on disk I/O. The
92 $offset argument specifies the starting point from which data is to 134 $offset argument specifies the starting point from which data is to
93 be read and $length specifies the number of bytes to be read. I/O is 135 be read and $length specifies the number of bytes to be read. I/O is
94 performed in whole pages, so that offset is effectively rounded down 136 performed in whole pages, so that offset is effectively rounded down
95 to a page boundary and bytes are read up to the next page boundary 137 to a page boundary and bytes are read up to the next page boundary
96 greater than or equal to (off-set+length). aio_readahead() does not 138 greater than or equal to (off-set+length). "aio_readahead" does not
97 read beyond the end of the file. The current file offset of the file 139 read beyond the end of the file. The current file offset of the file
98 is left unchanged. 140 is left unchanged.
141
142 If that syscall doesn't exist (likely if your OS isn't Linux) it
143 will be emulated by simply reading the data, which would have a
144 similar effect.
99 145
100 aio_stat $fh_or_path, $callback 146 aio_stat $fh_or_path, $callback
101 aio_lstat $fh, $callback 147 aio_lstat $fh, $callback
102 Works like perl's "stat" or "lstat" in void context. The callback 148 Works like perl's "stat" or "lstat" in void context. The callback
103 will be called after the stat and the results will be available 149 will be called after the stat and the results will be available
… …
120 166
121 aio_unlink $pathname, $callback 167 aio_unlink $pathname, $callback
122 Asynchronously unlink (delete) a file and call the callback with the 168 Asynchronously unlink (delete) a file and call the callback with the
123 result code. 169 result code.
124 170
171 aio_rmdir $pathname, $callback
172 Asynchronously rmdir (delete) a directory and call the callback with
173 the result code.
174
125 aio_fsync $fh, $callback 175 aio_fsync $fh, $callback
126 Asynchronously call fsync on the given filehandle and call the 176 Asynchronously call fsync on the given filehandle and call the
127 callback with the fsync result code. 177 callback with the fsync result code.
128 178
129 aio_fdatasync $fh, $callback 179 aio_fdatasync $fh, $callback
130 Asynchronously call fdatasync on the given filehandle and call the 180 Asynchronously call fdatasync on the given filehandle and call the
131 callback with the fdatasync result code. 181 callback with the fdatasync result code.
132 182
183 If this call isn't available because your OS lacks it or it couldn't
184 be detected, it will be emulated by calling "fsync" instead.
185
133 SUPPORT FUNCTIONS 186 SUPPORT FUNCTIONS
134 $fileno = IO::AIO::poll_fileno 187 $fileno = IO::AIO::poll_fileno
135 Return the *request result pipe filehandle*. This filehandle must be 188 Return the *request result pipe file descriptor*. This filehandle
136 polled for reading by some mechanism outside this module (e.g. Event 189 must be polled for reading by some mechanism outside this module
137 or select, see below). If the pipe becomes readable you have to call 190 (e.g. Event or select, see below or the SYNOPSIS). If the pipe
138 "poll_cb" to check the results. 191 becomes readable you have to call "poll_cb" to check the results.
139 192
140 See "poll_cb" for an example. 193 See "poll_cb" for an example.
141 194
142 IO::AIO::poll_cb 195 IO::AIO::poll_cb
143 Process all outstanding events on the result pipe. You have to call 196 Process all outstanding events on the result pipe. You have to call
144 this regularly. Returns the number of events processed. Returns 197 this regularly. Returns the number of events processed. Returns
145 immediately when no events are outstanding. 198 immediately when no events are outstanding.
146 199
147 You can use Event to multiplex, e.g.: 200 Example: Install an Event watcher that automatically calls
201 IO::AIO::poll_cb with high priority:
148 202
149 Event->io (fd => IO::AIO::poll_fileno, 203 Event->io (fd => IO::AIO::poll_fileno,
150 poll => 'r', async => 1, 204 poll => 'r', async => 1,
151 cb => \&IO::AIO::poll_cb); 205 cb => \&IO::AIO::poll_cb);
152 206
153 IO::AIO::poll_wait 207 IO::AIO::poll_wait
154 Wait till the result filehandle becomes ready for reading (simply 208 Wait till the result filehandle becomes ready for reading (simply
155 does a select on the filehandle. This is useful if you want to 209 does a "select" on the filehandle. This is useful if you want to
156 synchronously wait for some requests to finish). 210 synchronously wait for some requests to finish).
157 211
158 See "nreqs" for an example. 212 See "nreqs" for an example.
159 213
160 IO::AIO::nreqs 214 IO::AIO::nreqs
161 Returns the number of requests currently outstanding. 215 Returns the number of requests currently outstanding (i.e. for which
216 their callback has not been invoked yet).
162 217
163 Example: wait till there are no outstanding requests anymore: 218 Example: wait till there are no outstanding requests anymore:
164 219
165 IO::AIO::poll_wait, IO::AIO::poll_cb 220 IO::AIO::poll_wait, IO::AIO::poll_cb
166 while IO::AIO::nreqs; 221 while IO::AIO::nreqs;
222
223 IO::AIO::flush
224 Wait till all outstanding AIO requests have been handled.
225
226 Strictly equivalent to:
227
228 IO::AIO::poll_wait, IO::AIO::poll_cb
229 while IO::AIO::nreqs;
230
231 IO::AIO::poll
232 Waits until some requests have been handled.
233
234 Strictly equivalent to:
235
236 IO::AIO::poll_wait, IO::AIO::poll_cb
237 if IO::AIO::nreqs;
167 238
168 IO::AIO::min_parallel $nthreads 239 IO::AIO::min_parallel $nthreads
169 Set the minimum number of AIO threads to $nthreads. The default is 240 Set the minimum number of AIO threads to $nthreads. The default is
170 1, which means a single asynchronous operation can be done at one 241 1, which means a single asynchronous operation can be done at one
171 time (the number of outstanding operations, however, is unlimited). 242 time (the number of outstanding operations, however, is unlimited).
… …
199 If you queue up many requests in a loop it it often improves speed 270 If you queue up many requests in a loop it it often improves speed
200 if you set this to a relatively low number, such as 100. 271 if you set this to a relatively low number, such as 100.
201 272
202 Under normal circumstances you don't need to call this function. 273 Under normal circumstances you don't need to call this function.
203 274
275 FORK BEHAVIOUR
276 IO::AIO handles all outstanding AIO requests before the fork, destroys
277 all AIO threads, and recreates them in both the parent and the child
278 after the fork.
279
204SEE ALSO 280SEE ALSO
205 Coro, Linux::AIO. 281 Coro, Linux::AIO.
206 282
207AUTHOR 283AUTHOR
208 Marc Lehmann <schmorp@schmorp.de> 284 Marc Lehmann <schmorp@schmorp.de>

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