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Revision 1.6 by root, Mon Jul 11 03:29:39 2005 UTC vs.
Revision 1.12 by root, Tue Aug 23 00:05:00 2005 UTC

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20 poll => 'r', 20 poll => 'r',
21 cb => \&IO::AIO::poll_cb); 21 cb => \&IO::AIO::poll_cb);
22 22
23 # Glib/Gtk2 23 # Glib/Gtk2
24 add_watch Glib::IO IO::AIO::poll_fileno, 24 add_watch Glib::IO IO::AIO::poll_fileno,
25 in => sub { IO::AIO::poll_cb, 1 }; 25 in => sub { IO::AIO::poll_cb; 1 };
26 26
27 # Tk 27 # Tk
28 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "", 28 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
29 readable => \&IO::AIO::poll_cb); 29 readable => \&IO::AIO::poll_cb);
30 30
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45 currently, for example), and they would only support aio_read and 45 currently, for example), and they would only support aio_read and
46 aio_write, so the remaining functionality would have to be implemented 46 aio_write, so the remaining functionality would have to be implemented
47 using threads anyway. 47 using threads anyway.
48 48
49 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
50 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.
51 53
52FUNCTIONS 54FUNCTIONS
53 AIO FUNCTIONS 55 AIO FUNCTIONS
54 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
55 with the same name (sans "aio_"). The arguments are similar or 57 with the same name (sans "aio_"). The arguments are similar or
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57 argument which must be a code reference. This code reference will get 59 argument which must be a code reference. This code reference will get
58 called with the syscall return code (e.g. most syscalls return -1 on 60 called with the syscall return code (e.g. most syscalls return -1 on
59 error, unlike perl, which usually delivers "false") as it's sole 61 error, unlike perl, which usually delivers "false") as it's sole
60 argument when the given syscall has been executed asynchronously. 62 argument when the given syscall has been executed asynchronously.
61 63
62 All functions that expect a filehandle will also accept a file 64 All functions expecting a filehandle keep a copy of the filehandle
63 descriptor. 65 internally until the request has finished.
64 66
65 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
66 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
67 directory could have changed. Alternatively, you can make sure that you 69 is being executed, the current working directory could have changed.
68 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.
69 79
70 aio_open $pathname, $flags, $mode, $callback 80 aio_open $pathname, $flags, $mode, $callback
71 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
72 newly created filehandle for the file. 82 newly created filehandle for the file.
73 83
74 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,
75 above, for an explanation. 85 above, for an explanation.
76 86
77 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.
78 They are the same as used in "sysopen". 88 They are the same as used by "sysopen".
89
90 Likewise, $mode specifies the mode of the newly created file, if it
91 didn't exist and "O_CREAT" has been given, just like perl's
92 "sysopen", except that it is mandatory (i.e. use 0 if you don't
93 create new files, and 0666 or 0777 if you do).
79 94
80 Example: 95 Example:
81 96
82 aio_open "/etc/passwd", O_RDONLY, 0, sub { 97 aio_open "/etc/passwd", O_RDONLY, 0, sub {
83 if ($_[0]) { 98 if ($_[0]) {
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90 105
91 aio_close $fh, $callback 106 aio_close $fh, $callback
92 Asynchronously close a file and call the callback with the result 107 Asynchronously close a file and call the callback with the result
93 code. *WARNING:* although accepted, you should not pass in a perl 108 code. *WARNING:* although accepted, you should not pass in a perl
94 filehandle here, as perl will likely close the file descriptor 109 filehandle here, as perl will likely close the file descriptor
95 itself when the filehandle is destroyed. Normally, you can safely 110 another time when the filehandle is destroyed. Normally, you can
96 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.
97 115
98 aio_read $fh,$offset,$length, $data,$dataoffset,$callback 116 aio_read $fh,$offset,$length, $data,$dataoffset,$callback
99 aio_write $fh,$offset,$length, $data,$dataoffset,$callback 117 aio_write $fh,$offset,$length, $data,$dataoffset,$callback
100 Reads or writes "length" bytes from the specified "fh" and "offset" 118 Reads or writes "length" bytes from the specified "fh" and "offset"
101 into the scalar given by "data" and offset "dataoffset" and calls 119 into the scalar given by "data" and offset "dataoffset" and calls
102 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
103 error, just like the syscall). 121 error, just like the syscall).
104 122
123 The $data scalar *MUST NOT* be modified in any way while the request
124 is outstanding. Modifying it can result in segfaults or WW3 (if the
125 necessary/optional hardware is installed).
126
105 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at 127 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
106 offset 0 within the scalar: 128 offset 0 within the scalar:
107 129
108 aio_read $fh, 7, 15, $buffer, 0, sub { 130 aio_read $fh, 7, 15, $buffer, 0, sub {
109 $_[0] > 0 or die "read error: $!"; 131 $_[0] > 0 or die "read error: $!";
110 print "read $_[0] bytes: <$buffer>\n"; 132 print "read $_[0] bytes: <$buffer>\n";
111 }; 133 };
112 134
135 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback
136 Tries to copy $length bytes from $in_fh to $out_fh. It starts
137 reading at byte offset $in_offset, and starts writing at the current
138 file offset of $out_fh. Because of that, it is not safe to issue
139 more than one "aio_sendfile" per $out_fh, as they will interfere
140 with each other.
141
142 This call tries to make use of a native "sendfile" syscall to
143 provide zero-copy operation. For this to work, $out_fh should refer
144 to a socket, and $in_fh should refer to mmap'able file.
145
146 If the native sendfile call fails or is not implemented, it will be
147 emulated, so you can call "aio_sendfile" on any type of filehandle
148 regardless of the limitations of the operating system.
149
150 Please note, however, that "aio_sendfile" can read more bytes from
151 $in_fh than are written, and there is no way to find out how many
152 bytes have been read from "aio_sendfile" alone, as "aio_sendfile"
153 only provides the number of bytes written to $out_fh. Only if the
154 result value equals $length one can assume that $length bytes have
155 been read.
156
113 aio_readahead $fh,$offset,$length, $callback 157 aio_readahead $fh,$offset,$length, $callback
114 Asynchronously reads the specified byte range into the page cache,
115 using the "readahead" syscall. If that syscall doesn't exist (likely
116 if your OS isn't Linux) the status will be -1 and $! is set to
117 ENOSYS.
118
119 readahead() populates the page cache with data from a file so that 158 "aio_readahead" populates the page cache with data from a file so
120 subsequent reads from that file will not block on disk I/O. The 159 that subsequent reads from that file will not block on disk I/O. The
121 $offset argument specifies the starting point from which data is to 160 $offset argument specifies the starting point from which data is to
122 be read and $length specifies the number of bytes to be read. I/O is 161 be read and $length specifies the number of bytes to be read. I/O is
123 performed in whole pages, so that offset is effectively rounded down 162 performed in whole pages, so that offset is effectively rounded down
124 to a page boundary and bytes are read up to the next page boundary 163 to a page boundary and bytes are read up to the next page boundary
125 greater than or equal to (off-set+length). aio_readahead() does not 164 greater than or equal to (off-set+length). "aio_readahead" does not
126 read beyond the end of the file. The current file offset of the file 165 read beyond the end of the file. The current file offset of the file
127 is left unchanged. 166 is left unchanged.
167
168 If that syscall doesn't exist (likely if your OS isn't Linux) it
169 will be emulated by simply reading the data, which would have a
170 similar effect.
128 171
129 aio_stat $fh_or_path, $callback 172 aio_stat $fh_or_path, $callback
130 aio_lstat $fh, $callback 173 aio_lstat $fh, $callback
131 Works like perl's "stat" or "lstat" in void context. The callback 174 Works like perl's "stat" or "lstat" in void context. The callback
132 will be called after the stat and the results will be available 175 will be called after the stat and the results will be available
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149 192
150 aio_unlink $pathname, $callback 193 aio_unlink $pathname, $callback
151 Asynchronously unlink (delete) a file and call the callback with the 194 Asynchronously unlink (delete) a file and call the callback with the
152 result code. 195 result code.
153 196
197 aio_rmdir $pathname, $callback
198 Asynchronously rmdir (delete) a directory and call the callback with
199 the result code.
200
154 aio_fsync $fh, $callback 201 aio_fsync $fh, $callback
155 Asynchronously call fsync on the given filehandle and call the 202 Asynchronously call fsync on the given filehandle and call the
156 callback with the fsync result code. 203 callback with the fsync result code.
157 204
158 aio_fdatasync $fh, $callback 205 aio_fdatasync $fh, $callback
159 Asynchronously call fdatasync on the given filehandle and call the 206 Asynchronously call fdatasync on the given filehandle and call the
160 callback with the fdatasync result code. 207 callback with the fdatasync result code.
161 208
209 If this call isn't available because your OS lacks it or it couldn't
210 be detected, it will be emulated by calling "fsync" instead.
211
162 SUPPORT FUNCTIONS 212 SUPPORT FUNCTIONS
163 $fileno = IO::AIO::poll_fileno 213 $fileno = IO::AIO::poll_fileno
164 Return the *request result pipe filehandle*. This filehandle must be 214 Return the *request result pipe file descriptor*. This filehandle
165 polled for reading by some mechanism outside this module (e.g. Event 215 must be polled for reading by some mechanism outside this module
166 or select, see below). If the pipe becomes readable you have to call 216 (e.g. Event or select, see below or the SYNOPSIS). If the pipe
167 "poll_cb" to check the results. 217 becomes readable you have to call "poll_cb" to check the results.
168 218
169 See "poll_cb" for an example. 219 See "poll_cb" for an example.
170 220
171 IO::AIO::poll_cb 221 IO::AIO::poll_cb
172 Process all outstanding events on the result pipe. You have to call 222 Process all outstanding events on the result pipe. You have to call
173 this regularly. Returns the number of events processed. Returns 223 this regularly. Returns the number of events processed. Returns
174 immediately when no events are outstanding. 224 immediately when no events are outstanding.
175 225
176 You can use Event to multiplex, e.g.: 226 Example: Install an Event watcher that automatically calls
227 IO::AIO::poll_cb with high priority:
177 228
178 Event->io (fd => IO::AIO::poll_fileno, 229 Event->io (fd => IO::AIO::poll_fileno,
179 poll => 'r', async => 1, 230 poll => 'r', async => 1,
180 cb => \&IO::AIO::poll_cb); 231 cb => \&IO::AIO::poll_cb);
181 232
182 IO::AIO::poll_wait 233 IO::AIO::poll_wait
183 Wait till the result filehandle becomes ready for reading (simply 234 Wait till the result filehandle becomes ready for reading (simply
184 does a select on the filehandle. This is useful if you want to 235 does a "select" on the filehandle. This is useful if you want to
185 synchronously wait for some requests to finish). 236 synchronously wait for some requests to finish).
186 237
187 See "nreqs" for an example. 238 See "nreqs" for an example.
188 239
189 IO::AIO::nreqs 240 IO::AIO::nreqs
190 Returns the number of requests currently outstanding. 241 Returns the number of requests currently outstanding (i.e. for which
242 their callback has not been invoked yet).
191 243
192 Example: wait till there are no outstanding requests anymore: 244 Example: wait till there are no outstanding requests anymore:
193 245
194 IO::AIO::poll_wait, IO::AIO::poll_cb 246 IO::AIO::poll_wait, IO::AIO::poll_cb
195 while IO::AIO::nreqs; 247 while IO::AIO::nreqs;
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209 261
210 IO::AIO::poll_wait, IO::AIO::poll_cb 262 IO::AIO::poll_wait, IO::AIO::poll_cb
211 if IO::AIO::nreqs; 263 if IO::AIO::nreqs;
212 264
213 IO::AIO::min_parallel $nthreads 265 IO::AIO::min_parallel $nthreads
214 Set the minimum number of AIO threads to $nthreads. The default is 266 Set the minimum number of AIO threads to $nthreads. The current
215 1, which means a single asynchronous operation can be done at one 267 default is 4, which means four asynchronous operations can be done
216 time (the number of outstanding operations, however, is unlimited). 268 at one time (the number of outstanding operations, however, is
269 unlimited).
270
271 IO::AIO starts threads only on demand, when an AIO request is queued
272 and no free thread exists.
217 273
218 It is recommended to keep the number of threads low, as some Linux 274 It is recommended to keep the number of threads low, as some Linux
219 kernel versions will scale negatively with the number of threads 275 kernel versions will scale negatively with the number of threads
220 (higher parallelity => MUCH higher latency). With current Linux 2.6 276 (higher parallelity => MUCH higher latency). With current Linux 2.6
221 versions, 4-32 threads should be fine. 277 versions, 4-32 threads should be fine.
222 278
223 Under normal circumstances you don't need to call this function, as 279 Under most circumstances you don't need to call this function, as
224 this module automatically starts some threads (the exact number 280 the module selects a default that is suitable for low to moderate
225 might change, and is currently 4). 281 load.
226 282
227 IO::AIO::max_parallel $nthreads 283 IO::AIO::max_parallel $nthreads
228 Sets the maximum number of AIO threads to $nthreads. If more than 284 Sets the maximum number of AIO threads to $nthreads. If more than
229 the specified number of threads are currently running, kill them. 285 the specified number of threads are currently running, this function
230 This function blocks until the limit is reached. 286 kills them. This function blocks until the limit is reached.
287
288 While $nthreads are zero, aio requests get queued but not executed
289 until the number of threads has been increased again.
231 290
232 This module automatically runs "max_parallel 0" at program end, to 291 This module automatically runs "max_parallel 0" at program end, to
233 ensure that all threads are killed and that there are no outstanding 292 ensure that all threads are killed and that there are no outstanding
234 requests. 293 requests.
235 294
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239 Sets the maximum number of outstanding requests to $nreqs. If you 298 Sets the maximum number of outstanding requests to $nreqs. If you
240 try to queue up more than this number of requests, the caller will 299 try to queue up more than this number of requests, the caller will
241 block until some requests have been handled. 300 block until some requests have been handled.
242 301
243 The default is very large, so normally there is no practical limit. 302 The default is very large, so normally there is no practical limit.
244 If you queue up many requests in a loop it it often improves speed 303 If you queue up many requests in a loop it often improves speed if
245 if you set this to a relatively low number, such as 100. 304 you set this to a relatively low number, such as 100.
246 305
247 Under normal circumstances you don't need to call this function. 306 Under normal circumstances you don't need to call this function.
307
308 FORK BEHAVIOUR
309 Before the fork, IO::AIO enters a quiescent state where no requests can
310 be added in other threads and no results will be processed. After the
311 fork the parent simply leaves the quiescent state and continues
312 request/result processing, while the child clears the request/result
313 queue (so the requests started before the fork will only be handled in
314 the parent). Threats will be started on demand until the limit ste in
315 the parent process has been reached again.
248 316
249SEE ALSO 317SEE ALSO
250 Coro, Linux::AIO. 318 Coro, Linux::AIO.
251 319
252AUTHOR 320AUTHOR

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