… | |
… | |
13 | |
13 | |
14 | aio_read $fh, 30000, 1024, $buffer, 0, sub { |
14 | aio_read $fh, 30000, 1024, $buffer, 0, sub { |
15 | $_[0] > 0 or die "read error: $!"; |
15 | $_[0] > 0 or die "read error: $!"; |
16 | }; |
16 | }; |
17 | |
17 | |
18 | # Event |
18 | # version 2+ has request and group objects |
|
|
19 | use IO::AIO 2; |
|
|
20 | |
|
|
21 | aioreq_pri 4; # give next request a very high priority |
|
|
22 | my $req = aio_unlink "/tmp/file", sub { }; |
|
|
23 | $req->cancel; # cancel request if still in queue |
|
|
24 | |
|
|
25 | my $grp = aio_group sub { print "all stats done\n" }; |
|
|
26 | add $grp aio_stat "..." for ...; |
|
|
27 | |
|
|
28 | # AnyEvent integration |
|
|
29 | open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!"; |
|
|
30 | my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb }); |
|
|
31 | |
|
|
32 | # Event integration |
19 | Event->io (fd => IO::AIO::poll_fileno, |
33 | Event->io (fd => IO::AIO::poll_fileno, |
20 | poll => 'r', |
34 | poll => 'r', |
21 | cb => \&IO::AIO::poll_cb); |
35 | cb => \&IO::AIO::poll_cb); |
22 | |
36 | |
23 | # Glib/Gtk2 |
37 | # Glib/Gtk2 integration |
24 | add_watch Glib::IO IO::AIO::poll_fileno, |
38 | add_watch Glib::IO IO::AIO::poll_fileno, |
25 | in => sub { IO::AIO::poll_cb; 1 }; |
39 | in => sub { IO::AIO::poll_cb; 1 }; |
26 | |
40 | |
27 | # Tk |
41 | # Tk integration |
28 | Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "", |
42 | Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "", |
29 | readable => \&IO::AIO::poll_cb); |
43 | readable => \&IO::AIO::poll_cb); |
30 | |
44 | |
31 | # Danga::Socket |
45 | # Danga::Socket integration |
32 | Danga::Socket->AddOtherFds (IO::AIO::poll_fileno => |
46 | Danga::Socket->AddOtherFds (IO::AIO::poll_fileno => |
33 | \&IO::AIO::poll_cb); |
47 | \&IO::AIO::poll_cb); |
34 | |
48 | |
35 | DESCRIPTION |
49 | DESCRIPTION |
36 | This module implements asynchronous I/O using whatever means your |
50 | This module implements asynchronous I/O using whatever means your |
37 | operating system supports. |
51 | operating system supports. |
38 | |
52 | |
|
|
53 | Asynchronous means that operations that can normally block your program |
|
|
54 | (e.g. reading from disk) will be done asynchronously: the operation will |
|
|
55 | still block, but you can do something else in the meantime. This is |
|
|
56 | extremely useful for programs that need to stay interactive even when |
|
|
57 | doing heavy I/O (GUI programs, high performance network servers etc.), |
|
|
58 | but can also be used to easily do operations in parallel that are |
|
|
59 | normally done sequentially, e.g. stat'ing many files, which is much |
|
|
60 | faster on a RAID volume or over NFS when you do a number of stat |
|
|
61 | operations concurrently. |
|
|
62 | |
|
|
63 | While this works on all types of file descriptors (for example sockets), |
|
|
64 | using these functions on file descriptors that support nonblocking |
|
|
65 | operation (again, sockets, pipes etc.) is very inefficient. Use an event |
|
|
66 | loop for that (such as the Event module): IO::AIO will naturally fit |
|
|
67 | into such an event loop itself. |
|
|
68 | |
39 | Currently, a number of threads are started that execute your read/writes |
69 | In this version, a number of threads are started that execute your |
40 | and signal their completion. You don't need thread support in your libc |
70 | requests and signal their completion. You don't need thread support in |
41 | or perl, and the threads created by this module will not be visible to |
71 | perl, and the threads created by this module will not be visible to |
42 | the pthreads library. In the future, this module might make use of the |
72 | perl. In the future, this module might make use of the native aio |
43 | native aio functions available on many operating systems. However, they |
73 | functions available on many operating systems. However, they are often |
44 | are often not well-supported (Linux doesn't allow them on normal files |
74 | not well-supported or restricted (GNU/Linux doesn't allow them on normal |
45 | currently, for example), and they would only support aio_read and |
75 | files currently, for example), and they would only support aio_read and |
46 | aio_write, so the remaining functionality would have to be implemented |
76 | aio_write, so the remaining functionality would have to be implemented |
47 | using threads anyway. |
77 | using threads anyway. |
48 | |
78 | |
49 | Although the module will work with in the presence of other threads, it |
79 | Although the module will work with in the presence of other (Perl-) |
50 | is currently not reentrant, so use appropriate locking yourself, always |
80 | threads, it is currently not reentrant in any way, so use appropriate |
51 | call "poll_cb" from within the same thread, or never call "poll_cb" (or |
81 | locking yourself, always call "poll_cb" from within the same thread, or |
52 | other "aio_" functions) recursively. |
82 | never call "poll_cb" (or other "aio_" functions) recursively. |
|
|
83 | |
|
|
84 | EXAMPLE |
|
|
85 | This is a simple example that uses the Event module and loads |
|
|
86 | /etc/passwd asynchronously: |
|
|
87 | |
|
|
88 | use Fcntl; |
|
|
89 | use Event; |
|
|
90 | use IO::AIO; |
|
|
91 | |
|
|
92 | # register the IO::AIO callback with Event |
|
|
93 | Event->io (fd => IO::AIO::poll_fileno, |
|
|
94 | poll => 'r', |
|
|
95 | cb => \&IO::AIO::poll_cb); |
|
|
96 | |
|
|
97 | # queue the request to open /etc/passwd |
|
|
98 | aio_open "/etc/passwd", O_RDONLY, 0, sub { |
|
|
99 | my $fh = $_[0] |
|
|
100 | or die "error while opening: $!"; |
|
|
101 | |
|
|
102 | # stat'ing filehandles is generally non-blocking |
|
|
103 | my $size = -s $fh; |
|
|
104 | |
|
|
105 | # queue a request to read the file |
|
|
106 | my $contents; |
|
|
107 | aio_read $fh, 0, $size, $contents, 0, sub { |
|
|
108 | $_[0] == $size |
|
|
109 | or die "short read: $!"; |
|
|
110 | |
|
|
111 | close $fh; |
|
|
112 | |
|
|
113 | # file contents now in $contents |
|
|
114 | print $contents; |
|
|
115 | |
|
|
116 | # exit event loop and program |
|
|
117 | Event::unloop; |
|
|
118 | }; |
|
|
119 | }; |
|
|
120 | |
|
|
121 | # possibly queue up other requests, or open GUI windows, |
|
|
122 | # check for sockets etc. etc. |
|
|
123 | |
|
|
124 | # process events as long as there are some: |
|
|
125 | Event::loop; |
|
|
126 | |
|
|
127 | REQUEST ANATOMY AND LIFETIME |
|
|
128 | Every "aio_*" function creates a request. which is a C data structure |
|
|
129 | not directly visible to Perl. |
|
|
130 | |
|
|
131 | If called in non-void context, every request function returns a Perl |
|
|
132 | object representing the request. In void context, nothing is returned, |
|
|
133 | which saves a bit of memory. |
|
|
134 | |
|
|
135 | The perl object is a fairly standard ref-to-hash object. The hash |
|
|
136 | contents are not used by IO::AIO so you are free to store anything you |
|
|
137 | like in it. |
|
|
138 | |
|
|
139 | During their existance, aio requests travel through the following |
|
|
140 | states, in order: |
|
|
141 | |
|
|
142 | ready |
|
|
143 | Immediately after a request is created it is put into the ready |
|
|
144 | state, waiting for a thread to execute it. |
|
|
145 | |
|
|
146 | execute |
|
|
147 | A thread has accepted the request for processing and is currently |
|
|
148 | executing it (e.g. blocking in read). |
|
|
149 | |
|
|
150 | pending |
|
|
151 | The request has been executed and is waiting for result processing. |
|
|
152 | |
|
|
153 | While request submission and execution is fully asynchronous, result |
|
|
154 | processing is not and relies on the perl interpreter calling |
|
|
155 | "poll_cb" (or another function with the same effect). |
|
|
156 | |
|
|
157 | result |
|
|
158 | The request results are processed synchronously by "poll_cb". |
|
|
159 | |
|
|
160 | The "poll_cb" function will process all outstanding aio requests by |
|
|
161 | calling their callbacks, freeing memory associated with them and |
|
|
162 | managing any groups they are contained in. |
|
|
163 | |
|
|
164 | done |
|
|
165 | Request has reached the end of its lifetime and holds no resources |
|
|
166 | anymore (except possibly for the Perl object, but its connection to |
|
|
167 | the actual aio request is severed and calling its methods will |
|
|
168 | either do nothing or result in a runtime error). |
53 | |
169 | |
54 | FUNCTIONS |
170 | FUNCTIONS |
55 | AIO FUNCTIONS |
171 | AIO REQUEST FUNCTIONS |
56 | All the "aio_*" calls are more or less thin wrappers around the syscall |
172 | All the "aio_*" calls are more or less thin wrappers around the |
57 | with the same name (sans "aio_"). The arguments are similar or |
173 | syscall with the same name (sans "aio_"). The arguments are similar |
58 | identical, and they all accept an additional (and optional) $callback |
174 | or identical, and they all accept an additional (and optional) |
59 | argument which must be a code reference. This code reference will get |
175 | $callback argument which must be a code reference. This code |
60 | called with the syscall return code (e.g. most syscalls return -1 on |
176 | reference will get called with the syscall return code (e.g. most |
61 | error, unlike perl, which usually delivers "false") as it's sole |
177 | syscalls return -1 on error, unlike perl, which usually delivers |
62 | argument when the given syscall has been executed asynchronously. |
178 | "false") as it's sole argument when the given syscall has been |
|
|
179 | executed asynchronously. |
63 | |
180 | |
64 | All functions expecting a filehandle keep a copy of the filehandle |
181 | All functions expecting a filehandle keep a copy of the filehandle |
65 | internally until the request has finished. |
182 | internally until the request has finished. |
66 | |
183 | |
|
|
184 | All functions return request objects of type IO::AIO::REQ that allow |
|
|
185 | further manipulation of those requests while they are in-flight. |
|
|
186 | |
67 | The pathnames you pass to these routines *must* be absolute and encoded |
187 | The pathnames you pass to these routines *must* be absolute and |
68 | in byte form. The reason for the former is that at the time the request |
188 | encoded as octets. The reason for the former is that at the time the |
69 | is being executed, the current working directory could have changed. |
189 | request is being executed, the current working directory could have |
70 | Alternatively, you can make sure that you never change the current |
190 | changed. Alternatively, you can make sure that you never change the |
71 | working directory. |
191 | current working directory anywhere in the program and then use |
|
|
192 | relative paths. |
72 | |
193 | |
73 | To encode pathnames to byte form, either make sure you either: a) always |
194 | To encode pathnames as octets, either make sure you either: a) |
74 | pass in filenames you got from outside (command line, readdir etc.), b) |
195 | always pass in filenames you got from outside (command line, readdir |
75 | are ASCII or ISO 8859-1, c) use the Encode module and encode your |
196 | etc.) without tinkering, b) are ASCII or ISO 8859-1, c) use the |
76 | pathnames to the locale (or other) encoding in effect in the user |
197 | Encode module and encode your pathnames to the locale (or other) |
77 | environment, d) use Glib::filename_from_unicode on unicode filenames or |
198 | encoding in effect in the user environment, d) use |
78 | e) use something else. |
199 | Glib::filename_from_unicode on unicode filenames or e) use something |
|
|
200 | else to ensure your scalar has the correct contents. |
79 | |
201 | |
|
|
202 | This works, btw. independent of the internal UTF-8 bit, which |
|
|
203 | IO::AIO handles correctly wether it is set or not. |
|
|
204 | |
|
|
205 | $prev_pri = aioreq_pri [$pri] |
|
|
206 | Returns the priority value that would be used for the next |
|
|
207 | request and, if $pri is given, sets the priority for the next |
|
|
208 | aio request. |
|
|
209 | |
|
|
210 | The default priority is 0, the minimum and maximum priorities |
|
|
211 | are -4 and 4, respectively. Requests with higher priority will |
|
|
212 | be serviced first. |
|
|
213 | |
|
|
214 | The priority will be reset to 0 after each call to one of the |
|
|
215 | "aio_*" functions. |
|
|
216 | |
|
|
217 | Example: open a file with low priority, then read something from |
|
|
218 | it with higher priority so the read request is serviced before |
|
|
219 | other low priority open requests (potentially spamming the |
|
|
220 | cache): |
|
|
221 | |
|
|
222 | aioreq_pri -3; |
|
|
223 | aio_open ..., sub { |
|
|
224 | return unless $_[0]; |
|
|
225 | |
|
|
226 | aioreq_pri -2; |
|
|
227 | aio_read $_[0], ..., sub { |
|
|
228 | ... |
|
|
229 | }; |
|
|
230 | }; |
|
|
231 | |
|
|
232 | aioreq_nice $pri_adjust |
|
|
233 | Similar to "aioreq_pri", but subtracts the given value from the |
|
|
234 | current priority, so the effect is cumulative. |
|
|
235 | |
80 | aio_open $pathname, $flags, $mode, $callback |
236 | aio_open $pathname, $flags, $mode, $callback->($fh) |
81 | Asynchronously open or create a file and call the callback with a |
237 | Asynchronously open or create a file and call the callback with |
82 | newly created filehandle for the file. |
238 | a newly created filehandle for the file. |
83 | |
239 | |
84 | The pathname passed to "aio_open" must be absolute. See API NOTES, |
240 | The pathname passed to "aio_open" must be absolute. See API |
85 | above, for an explanation. |
241 | NOTES, above, for an explanation. |
86 | |
242 | |
87 | The $flags argument is a bitmask. See the "Fcntl" module for a list. |
243 | The $flags argument is a bitmask. See the "Fcntl" module for a |
88 | They are the same as used by "sysopen". |
244 | list. They are the same as used by "sysopen". |
89 | |
245 | |
90 | Likewise, $mode specifies the mode of the newly created file, if it |
246 | Likewise, $mode specifies the mode of the newly created file, if |
91 | didn't exist and "O_CREAT" has been given, just like perl's |
247 | it didn't exist and "O_CREAT" has been given, just like perl's |
92 | "sysopen", except that it is mandatory (i.e. use 0 if you don't |
248 | "sysopen", except that it is mandatory (i.e. use 0 if you don't |
93 | create new files, and 0666 or 0777 if you do). |
249 | create new files, and 0666 or 0777 if you do). |
94 | |
250 | |
95 | Example: |
251 | Example: |
96 | |
252 | |
97 | aio_open "/etc/passwd", O_RDONLY, 0, sub { |
253 | aio_open "/etc/passwd", O_RDONLY, 0, sub { |
98 | if ($_[0]) { |
254 | if ($_[0]) { |
99 | print "open successful, fh is $_[0]\n"; |
255 | print "open successful, fh is $_[0]\n"; |
100 | ... |
256 | ... |
101 | } else { |
257 | } else { |
102 | die "open failed: $!\n"; |
258 | die "open failed: $!\n"; |
|
|
259 | } |
103 | } |
260 | }; |
|
|
261 | |
|
|
262 | aio_close $fh, $callback->($status) |
|
|
263 | Asynchronously close a file and call the callback with the |
|
|
264 | result code. *WARNING:* although accepted, you should not pass |
|
|
265 | in a perl filehandle here, as perl will likely close the file |
|
|
266 | descriptor another time when the filehandle is destroyed. |
|
|
267 | Normally, you can safely call perls "close" or just let |
|
|
268 | filehandles go out of scope. |
|
|
269 | |
|
|
270 | This is supposed to be a bug in the API, so that might change. |
|
|
271 | It's therefore best to avoid this function. |
|
|
272 | |
|
|
273 | aio_read $fh,$offset,$length, $data,$dataoffset, |
|
|
274 | $callback->($retval) |
|
|
275 | aio_write $fh,$offset,$length, $data,$dataoffset, |
|
|
276 | $callback->($retval) |
|
|
277 | Reads or writes "length" bytes from the specified "fh" and |
|
|
278 | "offset" into the scalar given by "data" and offset "dataoffset" |
|
|
279 | and calls the callback without the actual number of bytes read |
|
|
280 | (or -1 on error, just like the syscall). |
|
|
281 | |
|
|
282 | The $data scalar *MUST NOT* be modified in any way while the |
|
|
283 | request is outstanding. Modifying it can result in segfaults or |
|
|
284 | WW3 (if the necessary/optional hardware is installed). |
|
|
285 | |
|
|
286 | Example: Read 15 bytes at offset 7 into scalar $buffer, starting |
|
|
287 | at offset 0 within the scalar: |
|
|
288 | |
|
|
289 | aio_read $fh, 7, 15, $buffer, 0, sub { |
|
|
290 | $_[0] > 0 or die "read error: $!"; |
|
|
291 | print "read $_[0] bytes: <$buffer>\n"; |
|
|
292 | }; |
|
|
293 | |
|
|
294 | aio_sendfile $out_fh, $in_fh, $in_offset, $length, |
|
|
295 | $callback->($retval) |
|
|
296 | Tries to copy $length bytes from $in_fh to $out_fh. It starts |
|
|
297 | reading at byte offset $in_offset, and starts writing at the |
|
|
298 | current file offset of $out_fh. Because of that, it is not safe |
|
|
299 | to issue more than one "aio_sendfile" per $out_fh, as they will |
|
|
300 | interfere with each other. |
|
|
301 | |
|
|
302 | This call tries to make use of a native "sendfile" syscall to |
|
|
303 | provide zero-copy operation. For this to work, $out_fh should |
|
|
304 | refer to a socket, and $in_fh should refer to mmap'able file. |
|
|
305 | |
|
|
306 | If the native sendfile call fails or is not implemented, it will |
|
|
307 | be emulated, so you can call "aio_sendfile" on any type of |
|
|
308 | filehandle regardless of the limitations of the operating |
|
|
309 | system. |
|
|
310 | |
|
|
311 | Please note, however, that "aio_sendfile" can read more bytes |
|
|
312 | from $in_fh than are written, and there is no way to find out |
|
|
313 | how many bytes have been read from "aio_sendfile" alone, as |
|
|
314 | "aio_sendfile" only provides the number of bytes written to |
|
|
315 | $out_fh. Only if the result value equals $length one can assume |
|
|
316 | that $length bytes have been read. |
|
|
317 | |
|
|
318 | aio_readahead $fh,$offset,$length, $callback->($retval) |
|
|
319 | "aio_readahead" populates the page cache with data from a file |
|
|
320 | so that subsequent reads from that file will not block on disk |
|
|
321 | I/O. The $offset argument specifies the starting point from |
|
|
322 | which data is to be read and $length specifies the number of |
|
|
323 | bytes to be read. I/O is performed in whole pages, so that |
|
|
324 | offset is effectively rounded down to a page boundary and bytes |
|
|
325 | are read up to the next page boundary greater than or equal to |
|
|
326 | (off-set+length). "aio_readahead" does not read beyond the end |
|
|
327 | of the file. The current file offset of the file is left |
|
|
328 | unchanged. |
|
|
329 | |
|
|
330 | If that syscall doesn't exist (likely if your OS isn't Linux) it |
|
|
331 | will be emulated by simply reading the data, which would have a |
|
|
332 | similar effect. |
|
|
333 | |
|
|
334 | aio_stat $fh_or_path, $callback->($status) |
|
|
335 | aio_lstat $fh, $callback->($status) |
|
|
336 | Works like perl's "stat" or "lstat" in void context. The |
|
|
337 | callback will be called after the stat and the results will be |
|
|
338 | available using "stat _" or "-s _" etc... |
|
|
339 | |
|
|
340 | The pathname passed to "aio_stat" must be absolute. See API |
|
|
341 | NOTES, above, for an explanation. |
|
|
342 | |
|
|
343 | Currently, the stats are always 64-bit-stats, i.e. instead of |
|
|
344 | returning an error when stat'ing a large file, the results will |
|
|
345 | be silently truncated unless perl itself is compiled with large |
|
|
346 | file support. |
|
|
347 | |
|
|
348 | Example: Print the length of /etc/passwd: |
|
|
349 | |
|
|
350 | aio_stat "/etc/passwd", sub { |
|
|
351 | $_[0] and die "stat failed: $!"; |
|
|
352 | print "size is ", -s _, "\n"; |
|
|
353 | }; |
|
|
354 | |
|
|
355 | aio_unlink $pathname, $callback->($status) |
|
|
356 | Asynchronously unlink (delete) a file and call the callback with |
|
|
357 | the result code. |
|
|
358 | |
|
|
359 | aio_mknod $path, $mode, $dev, $callback->($status) |
|
|
360 | [EXPERIMENTAL] |
|
|
361 | |
|
|
362 | Asynchronously create a device node (or fifo). See mknod(2). |
|
|
363 | |
|
|
364 | The only (POSIX-) portable way of calling this function is: |
|
|
365 | |
|
|
366 | aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... |
|
|
367 | |
|
|
368 | aio_link $srcpath, $dstpath, $callback->($status) |
|
|
369 | Asynchronously create a new link to the existing object at |
|
|
370 | $srcpath at the path $dstpath and call the callback with the |
|
|
371 | result code. |
|
|
372 | |
|
|
373 | aio_symlink $srcpath, $dstpath, $callback->($status) |
|
|
374 | Asynchronously create a new symbolic link to the existing object |
|
|
375 | at $srcpath at the path $dstpath and call the callback with the |
|
|
376 | result code. |
|
|
377 | |
|
|
378 | aio_rename $srcpath, $dstpath, $callback->($status) |
|
|
379 | Asynchronously rename the object at $srcpath to $dstpath, just |
|
|
380 | as rename(2) and call the callback with the result code. |
|
|
381 | |
|
|
382 | aio_rmdir $pathname, $callback->($status) |
|
|
383 | Asynchronously rmdir (delete) a directory and call the callback |
|
|
384 | with the result code. |
|
|
385 | |
|
|
386 | aio_readdir $pathname, $callback->($entries) |
|
|
387 | Unlike the POSIX call of the same name, "aio_readdir" reads an |
|
|
388 | entire directory (i.e. opendir + readdir + closedir). The |
|
|
389 | entries will not be sorted, and will NOT include the "." and |
|
|
390 | ".." entries. |
|
|
391 | |
|
|
392 | The callback a single argument which is either "undef" or an |
|
|
393 | array-ref with the filenames. |
|
|
394 | |
|
|
395 | aio_copy $srcpath, $dstpath, $callback->($status) |
|
|
396 | Try to copy the *file* (directories not supported as either |
|
|
397 | source or destination) from $srcpath to $dstpath and call the |
|
|
398 | callback with the 0 (error) or -1 ok. |
|
|
399 | |
|
|
400 | This is a composite request that it creates the destination file |
|
|
401 | with mode 0200 and copies the contents of the source file into |
|
|
402 | it using "aio_sendfile", followed by restoring atime, mtime, |
|
|
403 | access mode and uid/gid, in that order. |
|
|
404 | |
|
|
405 | If an error occurs, the partial destination file will be |
|
|
406 | unlinked, if possible, except when setting atime, mtime, access |
|
|
407 | mode and uid/gid, where errors are being ignored. |
|
|
408 | |
|
|
409 | aio_move $srcpath, $dstpath, $callback->($status) |
|
|
410 | Try to move the *file* (directories not supported as either |
|
|
411 | source or destination) from $srcpath to $dstpath and call the |
|
|
412 | callback with the 0 (error) or -1 ok. |
|
|
413 | |
|
|
414 | This is a composite request that tries to rename(2) the file |
|
|
415 | first. If rename files with "EXDEV", it copies the file with |
|
|
416 | "aio_copy" and, if that is successful, unlinking the $srcpath. |
|
|
417 | |
|
|
418 | aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) |
|
|
419 | Scans a directory (similar to "aio_readdir") but additionally |
|
|
420 | tries to efficiently separate the entries of directory $path |
|
|
421 | into two sets of names, directories you can recurse into |
|
|
422 | (directories), and ones you cannot recurse into (everything |
|
|
423 | else, including symlinks to directories). |
|
|
424 | |
|
|
425 | "aio_scandir" is a composite request that creates of many sub |
|
|
426 | requests_ $maxreq specifies the maximum number of outstanding |
|
|
427 | aio requests that this function generates. If it is "<= 0", then |
|
|
428 | a suitable default will be chosen (currently 4). |
|
|
429 | |
|
|
430 | On error, the callback is called without arguments, otherwise it |
|
|
431 | receives two array-refs with path-relative entry names. |
|
|
432 | |
|
|
433 | Example: |
|
|
434 | |
|
|
435 | aio_scandir $dir, 0, sub { |
|
|
436 | my ($dirs, $nondirs) = @_; |
|
|
437 | print "real directories: @$dirs\n"; |
|
|
438 | print "everything else: @$nondirs\n"; |
|
|
439 | }; |
|
|
440 | |
|
|
441 | Implementation notes. |
|
|
442 | |
|
|
443 | The "aio_readdir" cannot be avoided, but "stat()"'ing every |
|
|
444 | entry can. |
|
|
445 | |
|
|
446 | After reading the directory, the modification time, size etc. of |
|
|
447 | the directory before and after the readdir is checked, and if |
|
|
448 | they match (and isn't the current time), the link count will be |
|
|
449 | used to decide how many entries are directories (if >= 2). |
|
|
450 | Otherwise, no knowledge of the number of subdirectories will be |
|
|
451 | assumed. |
|
|
452 | |
|
|
453 | Then entries will be sorted into likely directories (everything |
|
|
454 | without a non-initial dot currently) and likely non-directories |
|
|
455 | (everything else). Then every entry plus an appended "/." will |
|
|
456 | be "stat"'ed, likely directories first. If that succeeds, it |
|
|
457 | assumes that the entry is a directory or a symlink to directory |
|
|
458 | (which will be checked seperately). This is often faster than |
|
|
459 | stat'ing the entry itself because filesystems might detect the |
|
|
460 | type of the entry without reading the inode data (e.g. ext2fs |
|
|
461 | filetype feature). |
|
|
462 | |
|
|
463 | If the known number of directories (link count - 2) has been |
|
|
464 | reached, the rest of the entries is assumed to be |
|
|
465 | non-directories. |
|
|
466 | |
|
|
467 | This only works with certainty on POSIX (= UNIX) filesystems, |
|
|
468 | which fortunately are the vast majority of filesystems around. |
|
|
469 | |
|
|
470 | It will also likely work on non-POSIX filesystems with reduced |
|
|
471 | efficiency as those tend to return 0 or 1 as link counts, which |
|
|
472 | disables the directory counting heuristic. |
|
|
473 | |
|
|
474 | aio_fsync $fh, $callback->($status) |
|
|
475 | Asynchronously call fsync on the given filehandle and call the |
|
|
476 | callback with the fsync result code. |
|
|
477 | |
|
|
478 | aio_fdatasync $fh, $callback->($status) |
|
|
479 | Asynchronously call fdatasync on the given filehandle and call |
|
|
480 | the callback with the fdatasync result code. |
|
|
481 | |
|
|
482 | If this call isn't available because your OS lacks it or it |
|
|
483 | couldn't be detected, it will be emulated by calling "fsync" |
|
|
484 | instead. |
|
|
485 | |
|
|
486 | aio_group $callback->(...) |
|
|
487 | This is a very special aio request: Instead of doing something, |
|
|
488 | it is a container for other aio requests, which is useful if you |
|
|
489 | want to bundle many requests into a single, composite, request |
|
|
490 | with a definite callback and the ability to cancel the whole |
|
|
491 | request with its subrequests. |
|
|
492 | |
|
|
493 | Returns an object of class IO::AIO::GRP. See its documentation |
|
|
494 | below for more info. |
|
|
495 | |
|
|
496 | Example: |
|
|
497 | |
|
|
498 | my $grp = aio_group sub { |
|
|
499 | print "all stats done\n"; |
|
|
500 | }; |
|
|
501 | |
|
|
502 | add $grp |
|
|
503 | (aio_stat ...), |
|
|
504 | (aio_stat ...), |
|
|
505 | ...; |
|
|
506 | |
|
|
507 | aio_nop $callback->() |
|
|
508 | This is a special request - it does nothing in itself and is |
|
|
509 | only used for side effects, such as when you want to add a dummy |
|
|
510 | request to a group so that finishing the requests in the group |
|
|
511 | depends on executing the given code. |
|
|
512 | |
|
|
513 | While this request does nothing, it still goes through the |
|
|
514 | execution phase and still requires a worker thread. Thus, the |
|
|
515 | callback will not be executed immediately but only after other |
|
|
516 | requests in the queue have entered their execution phase. This |
|
|
517 | can be used to measure request latency. |
|
|
518 | |
|
|
519 | IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED* |
|
|
520 | Mainly used for debugging and benchmarking, this aio request |
|
|
521 | puts one of the request workers to sleep for the given time. |
|
|
522 | |
|
|
523 | While it is theoretically handy to have simple I/O scheduling |
|
|
524 | requests like sleep and file handle readable/writable, the |
|
|
525 | overhead this creates is immense (it blocks a thread for a long |
|
|
526 | time) so do not use this function except to put your application |
|
|
527 | under artificial I/O pressure. |
|
|
528 | |
|
|
529 | IO::AIO::REQ CLASS |
|
|
530 | All non-aggregate "aio_*" functions return an object of this class |
|
|
531 | when called in non-void context. |
|
|
532 | |
|
|
533 | cancel $req |
|
|
534 | Cancels the request, if possible. Has the effect of skipping |
|
|
535 | execution when entering the execute state and skipping calling |
|
|
536 | the callback when entering the the result state, but will leave |
|
|
537 | the request otherwise untouched. That means that requests that |
|
|
538 | currently execute will not be stopped and resources held by the |
|
|
539 | request will not be freed prematurely. |
|
|
540 | |
|
|
541 | cb $req $callback->(...) |
|
|
542 | Replace (or simply set) the callback registered to the request. |
|
|
543 | |
|
|
544 | IO::AIO::GRP CLASS |
|
|
545 | This class is a subclass of IO::AIO::REQ, so all its methods apply |
|
|
546 | to objects of this class, too. |
|
|
547 | |
|
|
548 | A IO::AIO::GRP object is a special request that can contain multiple |
|
|
549 | other aio requests. |
|
|
550 | |
|
|
551 | You create one by calling the "aio_group" constructing function with |
|
|
552 | a callback that will be called when all contained requests have |
|
|
553 | entered the "done" state: |
|
|
554 | |
|
|
555 | my $grp = aio_group sub { |
|
|
556 | print "all requests are done\n"; |
104 | }; |
557 | }; |
105 | |
558 | |
106 | aio_close $fh, $callback |
559 | You add requests by calling the "add" method with one or more |
107 | Asynchronously close a file and call the callback with the result |
560 | "IO::AIO::REQ" objects: |
108 | code. *WARNING:* although accepted, you should not pass in a perl |
|
|
109 | filehandle here, as perl will likely close the file descriptor |
|
|
110 | another time when the filehandle is destroyed. Normally, you can |
|
|
111 | safely call perls "close" or just let filehandles go out of scope. |
|
|
112 | |
561 | |
113 | This is supposed to be a bug in the API, so that might change. It's |
562 | $grp->add (aio_unlink "..."); |
114 | therefore best to avoid this function. |
|
|
115 | |
563 | |
116 | aio_read $fh,$offset,$length, $data,$dataoffset,$callback |
564 | add $grp aio_stat "...", sub { |
117 | aio_write $fh,$offset,$length, $data,$dataoffset,$callback |
565 | $_[0] or return $grp->result ("error"); |
118 | Reads or writes "length" bytes from the specified "fh" and "offset" |
|
|
119 | into the scalar given by "data" and offset "dataoffset" and calls |
|
|
120 | the callback without the actual number of bytes read (or -1 on |
|
|
121 | error, just like the syscall). |
|
|
122 | |
566 | |
123 | The $data scalar *MUST NOT* be modified in any way while the request |
567 | # add another request dynamically, if first succeeded |
124 | is outstanding. Modifying it can result in segfaults or WW3 (if the |
568 | add $grp aio_open "...", sub { |
125 | necessary/optional hardware is installed). |
569 | $grp->result ("ok"); |
126 | |
570 | }; |
127 | Example: Read 15 bytes at offset 7 into scalar $buffer, starting at |
|
|
128 | offset 0 within the scalar: |
|
|
129 | |
|
|
130 | aio_read $fh, 7, 15, $buffer, 0, sub { |
|
|
131 | $_[0] > 0 or die "read error: $!"; |
|
|
132 | print "read $_[0] bytes: <$buffer>\n"; |
|
|
133 | }; |
571 | }; |
134 | |
572 | |
135 | aio_readahead $fh,$offset,$length, $callback |
573 | This makes it very easy to create composite requests (see the source |
136 | "aio_readahead" populates the page cache with data from a file so |
574 | of "aio_move" for an application) that work and feel like simple |
137 | that subsequent reads from that file will not block on disk I/O. The |
575 | requests. |
138 | $offset argument specifies the starting point from which data is to |
|
|
139 | be read and $length specifies the number of bytes to be read. I/O is |
|
|
140 | performed in whole pages, so that offset is effectively rounded down |
|
|
141 | to a page boundary and bytes are read up to the next page boundary |
|
|
142 | greater than or equal to (off-set+length). "aio_readahead" does not |
|
|
143 | read beyond the end of the file. The current file offset of the file |
|
|
144 | is left unchanged. |
|
|
145 | |
576 | |
146 | If that syscall doesn't exist (likely if your OS isn't Linux) it |
577 | * The IO::AIO::GRP objects will be cleaned up during calls to |
147 | will be emulated by simply reading the data, which would have a |
578 | "IO::AIO::poll_cb", just like any other request. |
148 | similar effect. |
579 | * They can be canceled like any other request. Canceling will cancel |
|
|
580 | not only the request itself, but also all requests it contains. |
|
|
581 | * They can also can also be added to other IO::AIO::GRP objects. |
|
|
582 | * You must not add requests to a group from within the group |
|
|
583 | callback (or any later time). |
149 | |
584 | |
150 | aio_stat $fh_or_path, $callback |
585 | Their lifetime, simplified, looks like this: when they are empty, |
151 | aio_lstat $fh, $callback |
586 | they will finish very quickly. If they contain only requests that |
152 | Works like perl's "stat" or "lstat" in void context. The callback |
587 | are in the "done" state, they will also finish. Otherwise they will |
153 | will be called after the stat and the results will be available |
588 | continue to exist. |
154 | using "stat _" or "-s _" etc... |
|
|
155 | |
589 | |
156 | The pathname passed to "aio_stat" must be absolute. See API NOTES, |
590 | That means after creating a group you have some time to add |
157 | above, for an explanation. |
591 | requests. And in the callbacks of those requests, you can add |
|
|
592 | further requests to the group. And only when all those requests have |
|
|
593 | finished will the the group itself finish. |
158 | |
594 | |
159 | Currently, the stats are always 64-bit-stats, i.e. instead of |
595 | add $grp ... |
160 | returning an error when stat'ing a large file, the results will be |
596 | $grp->add (...) |
161 | silently truncated unless perl itself is compiled with large file |
597 | Add one or more requests to the group. Any type of IO::AIO::REQ |
162 | support. |
598 | can be added, including other groups, as long as you do not |
|
|
599 | create circular dependencies. |
163 | |
600 | |
164 | Example: Print the length of /etc/passwd: |
601 | Returns all its arguments. |
165 | |
602 | |
166 | aio_stat "/etc/passwd", sub { |
603 | $grp->cancel_subs |
167 | $_[0] and die "stat failed: $!"; |
604 | Cancel all subrequests and clears any feeder, but not the group |
168 | print "size is ", -s _, "\n"; |
605 | request itself. Useful when you queued a lot of events but got a |
|
|
606 | result early. |
|
|
607 | |
|
|
608 | $grp->result (...) |
|
|
609 | Set the result value(s) that will be passed to the group |
|
|
610 | callback when all subrequests have finished and set thre groups |
|
|
611 | errno to the current value of errno (just like calling "errno" |
|
|
612 | without an error number). By default, no argument will be passed |
|
|
613 | and errno is zero. |
|
|
614 | |
|
|
615 | $grp->errno ([$errno]) |
|
|
616 | Sets the group errno value to $errno, or the current value of |
|
|
617 | errno when the argument is missing. |
|
|
618 | |
|
|
619 | Every aio request has an associated errno value that is restored |
|
|
620 | when the callback is invoked. This method lets you change this |
|
|
621 | value from its default (0). |
|
|
622 | |
|
|
623 | Calling "result" will also set errno, so make sure you either |
|
|
624 | set $! before the call to "result", or call c<errno> after it. |
|
|
625 | |
|
|
626 | feed $grp $callback->($grp) |
|
|
627 | Sets a feeder/generator on this group: every group can have an |
|
|
628 | attached generator that generates requests if idle. The idea |
|
|
629 | behind this is that, although you could just queue as many |
|
|
630 | requests as you want in a group, this might starve other |
|
|
631 | requests for a potentially long time. For example, "aio_scandir" |
|
|
632 | might generate hundreds of thousands "aio_stat" requests, |
|
|
633 | delaying any later requests for a long time. |
|
|
634 | |
|
|
635 | To avoid this, and allow incremental generation of requests, you |
|
|
636 | can instead a group and set a feeder on it that generates those |
|
|
637 | requests. The feed callback will be called whenever there are |
|
|
638 | few enough (see "limit", below) requests active in the group |
|
|
639 | itself and is expected to queue more requests. |
|
|
640 | |
|
|
641 | The feed callback can queue as many requests as it likes (i.e. |
|
|
642 | "add" does not impose any limits). |
|
|
643 | |
|
|
644 | If the feed does not queue more requests when called, it will be |
|
|
645 | automatically removed from the group. |
|
|
646 | |
|
|
647 | If the feed limit is 0, it will be set to 2 automatically. |
|
|
648 | |
|
|
649 | Example: |
|
|
650 | |
|
|
651 | # stat all files in @files, but only ever use four aio requests concurrently: |
|
|
652 | |
|
|
653 | my $grp = aio_group sub { print "finished\n" }; |
|
|
654 | limit $grp 4; |
|
|
655 | feed $grp sub { |
|
|
656 | my $file = pop @files |
|
|
657 | or return; |
|
|
658 | |
|
|
659 | add $grp aio_stat $file, sub { ... }; |
169 | }; |
660 | }; |
170 | |
661 | |
171 | aio_unlink $pathname, $callback |
662 | limit $grp $num |
172 | Asynchronously unlink (delete) a file and call the callback with the |
663 | Sets the feeder limit for the group: The feeder will be called |
173 | result code. |
664 | whenever the group contains less than this many requests. |
174 | |
665 | |
175 | aio_rmdir $pathname, $callback |
666 | Setting the limit to 0 will pause the feeding process. |
176 | Asynchronously rmdir (delete) a directory and call the callback with |
|
|
177 | the result code. |
|
|
178 | |
|
|
179 | aio_fsync $fh, $callback |
|
|
180 | Asynchronously call fsync on the given filehandle and call the |
|
|
181 | callback with the fsync result code. |
|
|
182 | |
|
|
183 | aio_fdatasync $fh, $callback |
|
|
184 | Asynchronously call fdatasync on the given filehandle and call the |
|
|
185 | callback with the fdatasync result code. |
|
|
186 | |
|
|
187 | If this call isn't available because your OS lacks it or it couldn't |
|
|
188 | be detected, it will be emulated by calling "fsync" instead. |
|
|
189 | |
667 | |
190 | SUPPORT FUNCTIONS |
668 | SUPPORT FUNCTIONS |
|
|
669 | EVENT PROCESSING AND EVENT LOOP INTEGRATION |
191 | $fileno = IO::AIO::poll_fileno |
670 | $fileno = IO::AIO::poll_fileno |
192 | Return the *request result pipe file descriptor*. This filehandle |
671 | Return the *request result pipe file descriptor*. This |
193 | must be polled for reading by some mechanism outside this module |
672 | filehandle must be polled for reading by some mechanism outside |
194 | (e.g. Event or select, see below or the SYNOPSIS). If the pipe |
673 | this module (e.g. Event or select, see below or the SYNOPSIS). |
195 | becomes readable you have to call "poll_cb" to check the results. |
674 | If the pipe becomes readable you have to call "poll_cb" to check |
|
|
675 | the results. |
196 | |
676 | |
197 | See "poll_cb" for an example. |
677 | See "poll_cb" for an example. |
198 | |
678 | |
199 | IO::AIO::poll_cb |
679 | IO::AIO::poll_cb |
200 | Process all outstanding events on the result pipe. You have to call |
680 | Process some outstanding events on the result pipe. You have to |
201 | this regularly. Returns the number of events processed. Returns |
681 | call this regularly. Returns the number of events processed. |
202 | immediately when no events are outstanding. |
682 | Returns immediately when no events are outstanding. The amount |
|
|
683 | of events processed depends on the settings of |
|
|
684 | "IO::AIO::max_poll_req" and "IO::AIO::max_poll_time". |
203 | |
685 | |
|
|
686 | If not all requests were processed for whatever reason, the |
|
|
687 | filehandle will still be ready when "poll_cb" returns. |
|
|
688 | |
204 | Example: Install an Event watcher that automatically calls |
689 | Example: Install an Event watcher that automatically calls |
205 | IO::AIO::poll_cb with high priority: |
690 | IO::AIO::poll_cb with high priority: |
206 | |
691 | |
207 | Event->io (fd => IO::AIO::poll_fileno, |
692 | Event->io (fd => IO::AIO::poll_fileno, |
208 | poll => 'r', async => 1, |
693 | poll => 'r', async => 1, |
209 | cb => \&IO::AIO::poll_cb); |
694 | cb => \&IO::AIO::poll_cb); |
210 | |
695 | |
|
|
696 | IO::AIO::max_poll_reqs $nreqs |
|
|
697 | IO::AIO::max_poll_time $seconds |
|
|
698 | These set the maximum number of requests (default 0, meaning |
|
|
699 | infinity) that are being processed by "IO::AIO::poll_cb" in one |
|
|
700 | call, respectively the maximum amount of time (default 0, |
|
|
701 | meaning infinity) spent in "IO::AIO::poll_cb" to process |
|
|
702 | requests (more correctly the mininum amount of time "poll_cb" is |
|
|
703 | allowed to use). |
|
|
704 | |
|
|
705 | Setting these is useful if you want to ensure some level of |
|
|
706 | interactiveness when perl is not fast enough to process all |
|
|
707 | requests in time. |
|
|
708 | |
|
|
709 | For interactive programs, values such as 0.01 to 0.1 should be |
|
|
710 | fine. |
|
|
711 | |
|
|
712 | Example: Install an Event watcher that automatically calls |
|
|
713 | IO::AIO::poll_some with low priority, to ensure that other parts |
|
|
714 | of the program get the CPU sometimes even under high AIO load. |
|
|
715 | |
|
|
716 | # try not to spend much more than 0.1s in poll_cb |
|
|
717 | IO::AIO::max_poll_time 0.1; |
|
|
718 | |
|
|
719 | # use a low priority so other tasks have priority |
|
|
720 | Event->io (fd => IO::AIO::poll_fileno, |
|
|
721 | poll => 'r', nice => 1, |
|
|
722 | cb => &IO::AIO::poll_cb); |
|
|
723 | |
211 | IO::AIO::poll_wait |
724 | IO::AIO::poll_wait |
212 | Wait till the result filehandle becomes ready for reading (simply |
725 | Wait till the result filehandle becomes ready for reading |
213 | does a "select" on the filehandle. This is useful if you want to |
726 | (simply does a "select" on the filehandle. This is useful if you |
214 | synchronously wait for some requests to finish). |
727 | want to synchronously wait for some requests to finish). |
215 | |
728 | |
216 | See "nreqs" for an example. |
729 | See "nreqs" for an example. |
217 | |
730 | |
218 | IO::AIO::nreqs |
731 | IO::AIO::poll |
219 | Returns the number of requests currently outstanding (i.e. for which |
732 | Waits until some requests have been handled. |
220 | their callback has not been invoked yet). |
|
|
221 | |
733 | |
222 | Example: wait till there are no outstanding requests anymore: |
734 | Strictly equivalent to: |
223 | |
735 | |
224 | IO::AIO::poll_wait, IO::AIO::poll_cb |
736 | IO::AIO::poll_wait, IO::AIO::poll_cb |
225 | while IO::AIO::nreqs; |
737 | if IO::AIO::nreqs; |
226 | |
738 | |
227 | IO::AIO::flush |
739 | IO::AIO::flush |
228 | Wait till all outstanding AIO requests have been handled. |
740 | Wait till all outstanding AIO requests have been handled. |
229 | |
741 | |
230 | Strictly equivalent to: |
742 | Strictly equivalent to: |
231 | |
743 | |
232 | IO::AIO::poll_wait, IO::AIO::poll_cb |
744 | IO::AIO::poll_wait, IO::AIO::poll_cb |
233 | while IO::AIO::nreqs; |
745 | while IO::AIO::nreqs; |
234 | |
746 | |
235 | IO::AIO::poll |
747 | CONTROLLING THE NUMBER OF THREADS |
236 | Waits until some requests have been handled. |
|
|
237 | |
|
|
238 | Strictly equivalent to: |
|
|
239 | |
|
|
240 | IO::AIO::poll_wait, IO::AIO::poll_cb |
|
|
241 | if IO::AIO::nreqs; |
|
|
242 | |
|
|
243 | IO::AIO::min_parallel $nthreads |
748 | IO::AIO::min_parallel $nthreads |
244 | Set the minimum number of AIO threads to $nthreads. The default is |
749 | Set the minimum number of AIO threads to $nthreads. The current |
245 | 1, which means a single asynchronous operation can be done at one |
750 | default is 8, which means eight asynchronous operations can |
246 | time (the number of outstanding operations, however, is unlimited). |
751 | execute concurrently at any one time (the number of outstanding |
|
|
752 | requests, however, is unlimited). |
247 | |
753 | |
|
|
754 | IO::AIO starts threads only on demand, when an AIO request is |
|
|
755 | queued and no free thread exists. Please note that queueing up a |
|
|
756 | hundred requests can create demand for a hundred threads, even |
|
|
757 | if it turns out that everything is in the cache and could have |
|
|
758 | been processed faster by a single thread. |
|
|
759 | |
248 | It is recommended to keep the number of threads low, as some Linux |
760 | It is recommended to keep the number of threads relatively low, |
249 | kernel versions will scale negatively with the number of threads |
761 | as some Linux kernel versions will scale negatively with the |
250 | (higher parallelity => MUCH higher latency). With current Linux 2.6 |
762 | number of threads (higher parallelity => MUCH higher latency). |
251 | versions, 4-32 threads should be fine. |
763 | With current Linux 2.6 versions, 4-32 threads should be fine. |
252 | |
764 | |
253 | Under normal circumstances you don't need to call this function, as |
765 | Under most circumstances you don't need to call this function, |
254 | this module automatically starts some threads (the exact number |
766 | as the module selects a default that is suitable for low to |
255 | might change, and is currently 4). |
767 | moderate load. |
256 | |
768 | |
257 | IO::AIO::max_parallel $nthreads |
769 | IO::AIO::max_parallel $nthreads |
258 | Sets the maximum number of AIO threads to $nthreads. If more than |
770 | Sets the maximum number of AIO threads to $nthreads. If more |
259 | the specified number of threads are currently running, kill them. |
771 | than the specified number of threads are currently running, this |
260 | This function blocks until the limit is reached. |
772 | function kills them. This function blocks until the limit is |
|
|
773 | reached. |
261 | |
774 | |
|
|
775 | While $nthreads are zero, aio requests get queued but not |
|
|
776 | executed until the number of threads has been increased again. |
|
|
777 | |
262 | This module automatically runs "max_parallel 0" at program end, to |
778 | This module automatically runs "max_parallel 0" at program end, |
263 | ensure that all threads are killed and that there are no outstanding |
779 | to ensure that all threads are killed and that there are no |
264 | requests. |
780 | outstanding requests. |
265 | |
781 | |
266 | Under normal circumstances you don't need to call this function. |
782 | Under normal circumstances you don't need to call this function. |
267 | |
783 | |
|
|
784 | IO::AIO::max_idle $nthreads |
|
|
785 | Limit the number of threads (default: 4) that are allowed to |
|
|
786 | idle (i.e., threads that did not get a request to process within |
|
|
787 | 10 seconds). That means if a thread becomes idle while $nthreads |
|
|
788 | other threads are also idle, it will free its resources and |
|
|
789 | exit. |
|
|
790 | |
|
|
791 | This is useful when you allow a large number of threads (e.g. |
|
|
792 | 100 or 1000) to allow for extremely high load situations, but |
|
|
793 | want to free resources under normal circumstances (1000 threads |
|
|
794 | can easily consume 30MB of RAM). |
|
|
795 | |
|
|
796 | The default is probably ok in most situations, especially if |
|
|
797 | thread creation is fast. If thread creation is very slow on your |
|
|
798 | system you might want to use larger values. |
|
|
799 | |
268 | $oldnreqs = IO::AIO::max_outstanding $nreqs |
800 | $oldmaxreqs = IO::AIO::max_outstanding $maxreqs |
|
|
801 | This is a very bad function to use in interactive programs |
|
|
802 | because it blocks, and a bad way to reduce concurrency because |
|
|
803 | it is inexact: Better use an "aio_group" together with a feed |
|
|
804 | callback. |
|
|
805 | |
269 | Sets the maximum number of outstanding requests to $nreqs. If you |
806 | Sets the maximum number of outstanding requests to $nreqs. If |
270 | try to queue up more than this number of requests, the caller will |
807 | you to queue up more than this number of requests, the next call |
271 | block until some requests have been handled. |
808 | to the "poll_cb" (and "poll_some" and other functions calling |
|
|
809 | "poll_cb") function will block until the limit is no longer |
|
|
810 | exceeded. |
272 | |
811 | |
273 | The default is very large, so normally there is no practical limit. |
812 | The default value is very large, so there is no practical limit |
274 | If you queue up many requests in a loop it it often improves speed |
813 | on the number of outstanding requests. |
275 | if you set this to a relatively low number, such as 100. |
|
|
276 | |
814 | |
277 | Under normal circumstances you don't need to call this function. |
815 | You can still queue as many requests as you want. Therefore, |
|
|
816 | "max_oustsanding" is mainly useful in simple scripts (with low |
|
|
817 | values) or as a stop gap to shield against fatal memory overflow |
|
|
818 | (with large values). |
|
|
819 | |
|
|
820 | STATISTICAL INFORMATION |
|
|
821 | IO::AIO::nreqs |
|
|
822 | Returns the number of requests currently in the ready, execute |
|
|
823 | or pending states (i.e. for which their callback has not been |
|
|
824 | invoked yet). |
|
|
825 | |
|
|
826 | Example: wait till there are no outstanding requests anymore: |
|
|
827 | |
|
|
828 | IO::AIO::poll_wait, IO::AIO::poll_cb |
|
|
829 | while IO::AIO::nreqs; |
|
|
830 | |
|
|
831 | IO::AIO::nready |
|
|
832 | Returns the number of requests currently in the ready state (not |
|
|
833 | yet executed). |
|
|
834 | |
|
|
835 | IO::AIO::npending |
|
|
836 | Returns the number of requests currently in the pending state |
|
|
837 | (executed, but not yet processed by poll_cb). |
278 | |
838 | |
279 | FORK BEHAVIOUR |
839 | FORK BEHAVIOUR |
|
|
840 | This module should do "the right thing" when the process using it |
|
|
841 | forks: |
|
|
842 | |
280 | Before the fork IO::AIO enters a quiescent state where no requests can |
843 | Before the fork, IO::AIO enters a quiescent state where no requests |
281 | be added in other threads and no results will be processed. After the |
844 | can be added in other threads and no results will be processed. |
282 | fork the parent simply leaves the quiescent state and continues |
845 | After the fork the parent simply leaves the quiescent state and |
283 | request/result processing, while the child clears the request/result |
846 | continues request/result processing, while the child frees the |
284 | queue and starts the same number of threads as were in use by the |
847 | request/result queue (so that the requests started before the fork |
285 | parent. |
848 | will only be handled in the parent). Threads will be started on |
|
|
849 | demand until the limit set in the parent process has been reached |
|
|
850 | again. |
|
|
851 | |
|
|
852 | In short: the parent will, after a short pause, continue as if fork |
|
|
853 | had not been called, while the child will act as if IO::AIO has not |
|
|
854 | been used yet. |
|
|
855 | |
|
|
856 | MEMORY USAGE |
|
|
857 | Per-request usage: |
|
|
858 | |
|
|
859 | Each aio request uses - depending on your architecture - around |
|
|
860 | 100-200 bytes of memory. In addition, stat requests need a stat |
|
|
861 | buffer (possibly a few hundred bytes), readdir requires a result |
|
|
862 | buffer and so on. Perl scalars and other data passed into aio |
|
|
863 | requests will also be locked and will consume memory till the |
|
|
864 | request has entered the done state. |
|
|
865 | |
|
|
866 | This is now awfully much, so queuing lots of requests is not usually |
|
|
867 | a problem. |
|
|
868 | |
|
|
869 | Per-thread usage: |
|
|
870 | |
|
|
871 | In the execution phase, some aio requests require more memory for |
|
|
872 | temporary buffers, and each thread requires a stack and other data |
|
|
873 | structures (usually around 16k-128k, depending on the OS). |
|
|
874 | |
|
|
875 | KNOWN BUGS |
|
|
876 | Known bugs will be fixed in the next release. |
286 | |
877 | |
287 | SEE ALSO |
878 | SEE ALSO |
288 | Coro, Linux::AIO. |
879 | Coro::AIO. |
289 | |
880 | |
290 | AUTHOR |
881 | AUTHOR |
291 | Marc Lehmann <schmorp@schmorp.de> |
882 | Marc Lehmann <schmorp@schmorp.de> |
292 | http://home.schmorp.de/ |
883 | http://home.schmorp.de/ |
293 | |
884 | |