… | |
… | |
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 | |
39 | Currently, a number of threads are started that execute your read/writes |
53 | 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 |
54 | 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 |
55 | 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 |
56 | perl. In the future, this module might make use of the native aio |
43 | native aio functions available on many operating systems. However, they |
57 | functions available on many operating systems. However, they are often |
44 | are often not well-supported (Linux doesn't allow them on normal files |
58 | not well-supported or restricted (Linux doesn't allow them on normal |
45 | currently, for example), and they would only support aio_read and |
59 | files currently, for example), and they would only support aio_read and |
46 | aio_write, so the remaining functionality would have to be implemented |
60 | aio_write, so the remaining functionality would have to be implemented |
47 | using threads anyway. |
61 | using threads anyway. |
48 | |
62 | |
49 | Although the module will work with in the presence of other threads, it |
63 | Although the module will work with in the presence of other (Perl-) |
50 | is currently not reentrant, so use appropriate locking yourself. |
64 | threads, it is currently not reentrant in any way, so use appropriate |
|
|
65 | locking yourself, always call "poll_cb" from within the same thread, or |
|
|
66 | never call "poll_cb" (or other "aio_" functions) recursively. |
|
|
67 | |
|
|
68 | REQUEST ANATOMY AND LIFETIME |
|
|
69 | Every "aio_*" function creates a request. which is a C data structure |
|
|
70 | not directly visible to Perl. |
|
|
71 | |
|
|
72 | If called in non-void context, every request function returns a Perl |
|
|
73 | object representing the request. In void context, nothing is returned, |
|
|
74 | which saves a bit of memory. |
|
|
75 | |
|
|
76 | The perl object is a fairly standard ref-to-hash object. The hash |
|
|
77 | contents are not used by IO::AIO so you are free to store anything you |
|
|
78 | like in it. |
|
|
79 | |
|
|
80 | During their existance, aio requests travel through the following |
|
|
81 | states, in order: |
|
|
82 | |
|
|
83 | ready |
|
|
84 | Immediately after a request is created it is put into the ready |
|
|
85 | state, waiting for a thread to execute it. |
|
|
86 | |
|
|
87 | execute |
|
|
88 | A thread has accepted the request for processing and is currently |
|
|
89 | executing it (e.g. blocking in read). |
|
|
90 | |
|
|
91 | pending |
|
|
92 | The request has been executed and is waiting for result processing. |
|
|
93 | |
|
|
94 | While request submission and execution is fully asynchronous, result |
|
|
95 | processing is not and relies on the perl interpreter calling |
|
|
96 | "poll_cb" (or another function with the same effect). |
|
|
97 | |
|
|
98 | result |
|
|
99 | The request results are processed synchronously by "poll_cb". |
|
|
100 | |
|
|
101 | The "poll_cb" function will process all outstanding aio requests by |
|
|
102 | calling their callbacks, freeing memory associated with them and |
|
|
103 | managing any groups they are contained in. |
|
|
104 | |
|
|
105 | done |
|
|
106 | Request has reached the end of its lifetime and holds no resources |
|
|
107 | anymore (except possibly for the Perl object, but its connection to |
|
|
108 | the actual aio request is severed and calling its methods will |
|
|
109 | either do nothing or result in a runtime error). |
51 | |
110 | |
52 | FUNCTIONS |
111 | FUNCTIONS |
53 | AIO FUNCTIONS |
112 | AIO FUNCTIONS |
54 | All the "aio_*" calls are more or less thin wrappers around the syscall |
113 | All the "aio_*" calls are more or less thin wrappers around the |
55 | with the same name (sans "aio_"). The arguments are similar or |
114 | syscall with the same name (sans "aio_"). The arguments are similar |
56 | identical, and they all accept an additional (and optional) $callback |
115 | or identical, and they all accept an additional (and optional) |
57 | argument which must be a code reference. This code reference will get |
116 | $callback argument which must be a code reference. This code |
58 | called with the syscall return code (e.g. most syscalls return -1 on |
117 | reference will get called with the syscall return code (e.g. most |
59 | error, unlike perl, which usually delivers "false") as it's sole |
118 | syscalls return -1 on error, unlike perl, which usually delivers |
60 | argument when the given syscall has been executed asynchronously. |
119 | "false") as it's sole argument when the given syscall has been |
|
|
120 | executed asynchronously. |
61 | |
121 | |
62 | All functions that expect a filehandle will also accept a file |
122 | All functions expecting a filehandle keep a copy of the filehandle |
63 | descriptor. |
123 | internally until the request has finished. |
64 | |
124 | |
|
|
125 | All requests return objects of type IO::AIO::REQ that allow further |
|
|
126 | manipulation of those requests while they are in-flight. |
|
|
127 | |
65 | The filenames you pass to these routines *must* be absolute. The reason |
128 | The pathnames you pass to these routines *must* be absolute and |
66 | is that at the time the request is being executed, the current working |
129 | encoded in byte form. The reason for the former is that at the time |
|
|
130 | the request is being executed, the current working directory could |
67 | directory could have changed. Alternatively, you can make sure that you |
131 | have changed. Alternatively, you can make sure that you never change |
68 | never change the current working directory. |
132 | the current working directory. |
69 | |
133 | |
|
|
134 | To encode pathnames to byte form, either make sure you either: a) |
|
|
135 | always pass in filenames you got from outside (command line, readdir |
|
|
136 | etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and |
|
|
137 | encode your pathnames to the locale (or other) encoding in effect in |
|
|
138 | the user environment, d) use Glib::filename_from_unicode on unicode |
|
|
139 | filenames or e) use something else. |
|
|
140 | |
|
|
141 | $prev_pri = aioreq_pri [$pri] |
|
|
142 | Returns the priority value that would be used for the next |
|
|
143 | request and, if $pri is given, sets the priority for the next |
|
|
144 | aio request. |
|
|
145 | |
|
|
146 | The default priority is 0, the minimum and maximum priorities |
|
|
147 | are -4 and 4, respectively. Requests with higher priority will |
|
|
148 | be serviced first. |
|
|
149 | |
|
|
150 | The priority will be reset to 0 after each call to one of the |
|
|
151 | "aio_*" functions. |
|
|
152 | |
|
|
153 | Example: open a file with low priority, then read something from |
|
|
154 | it with higher priority so the read request is serviced before |
|
|
155 | other low priority open requests (potentially spamming the |
|
|
156 | cache): |
|
|
157 | |
|
|
158 | aioreq_pri -3; |
|
|
159 | aio_open ..., sub { |
|
|
160 | return unless $_[0]; |
|
|
161 | |
|
|
162 | aioreq_pri -2; |
|
|
163 | aio_read $_[0], ..., sub { |
|
|
164 | ... |
|
|
165 | }; |
|
|
166 | }; |
|
|
167 | |
|
|
168 | aioreq_nice $pri_adjust |
|
|
169 | Similar to "aioreq_pri", but subtracts the given value from the |
|
|
170 | current priority, so effects are cumulative. |
|
|
171 | |
70 | aio_open $pathname, $flags, $mode, $callback |
172 | aio_open $pathname, $flags, $mode, $callback->($fh) |
71 | Asynchronously open or create a file and call the callback with a |
173 | Asynchronously open or create a file and call the callback with |
72 | newly created filehandle for the file. |
174 | a newly created filehandle for the file. |
73 | |
175 | |
74 | The pathname passed to "aio_open" must be absolute. See API NOTES, |
176 | The pathname passed to "aio_open" must be absolute. See API |
75 | above, for an explanation. |
177 | NOTES, above, for an explanation. |
76 | |
178 | |
77 | The $mode argument is a bitmask. See the "Fcntl" module for a list. |
179 | The $flags argument is a bitmask. See the "Fcntl" module for a |
78 | They are the same as used in "sysopen". |
180 | list. They are the same as used by "sysopen". |
79 | |
181 | |
|
|
182 | Likewise, $mode specifies the mode of the newly created file, if |
|
|
183 | it didn't exist and "O_CREAT" has been given, just like perl's |
|
|
184 | "sysopen", except that it is mandatory (i.e. use 0 if you don't |
|
|
185 | create new files, and 0666 or 0777 if you do). |
|
|
186 | |
80 | Example: |
187 | Example: |
81 | |
188 | |
82 | aio_open "/etc/passwd", O_RDONLY, 0, sub { |
189 | aio_open "/etc/passwd", O_RDONLY, 0, sub { |
83 | if ($_[0]) { |
190 | if ($_[0]) { |
84 | print "open successful, fh is $_[0]\n"; |
191 | print "open successful, fh is $_[0]\n"; |
85 | ... |
192 | ... |
86 | } else { |
193 | } else { |
87 | die "open failed: $!\n"; |
194 | die "open failed: $!\n"; |
|
|
195 | } |
88 | } |
196 | }; |
|
|
197 | |
|
|
198 | aio_close $fh, $callback->($status) |
|
|
199 | Asynchronously close a file and call the callback with the |
|
|
200 | result code. *WARNING:* although accepted, you should not pass |
|
|
201 | in a perl filehandle here, as perl will likely close the file |
|
|
202 | descriptor another time when the filehandle is destroyed. |
|
|
203 | Normally, you can safely call perls "close" or just let |
|
|
204 | filehandles go out of scope. |
|
|
205 | |
|
|
206 | This is supposed to be a bug in the API, so that might change. |
|
|
207 | It's therefore best to avoid this function. |
|
|
208 | |
|
|
209 | aio_read $fh,$offset,$length, $data,$dataoffset, |
|
|
210 | $callback->($retval) |
|
|
211 | aio_write $fh,$offset,$length, $data,$dataoffset, |
|
|
212 | $callback->($retval) |
|
|
213 | Reads or writes "length" bytes from the specified "fh" and |
|
|
214 | "offset" into the scalar given by "data" and offset "dataoffset" |
|
|
215 | and calls the callback without the actual number of bytes read |
|
|
216 | (or -1 on error, just like the syscall). |
|
|
217 | |
|
|
218 | The $data scalar *MUST NOT* be modified in any way while the |
|
|
219 | request is outstanding. Modifying it can result in segfaults or |
|
|
220 | WW3 (if the necessary/optional hardware is installed). |
|
|
221 | |
|
|
222 | Example: Read 15 bytes at offset 7 into scalar $buffer, starting |
|
|
223 | at offset 0 within the scalar: |
|
|
224 | |
|
|
225 | aio_read $fh, 7, 15, $buffer, 0, sub { |
|
|
226 | $_[0] > 0 or die "read error: $!"; |
|
|
227 | print "read $_[0] bytes: <$buffer>\n"; |
|
|
228 | }; |
|
|
229 | |
|
|
230 | aio_move $srcpath, $dstpath, $callback->($status) |
|
|
231 | Try to move the *file* (directories not supported as either |
|
|
232 | source or destination) from $srcpath to $dstpath and call the |
|
|
233 | callback with the 0 (error) or -1 ok. |
|
|
234 | |
|
|
235 | This is a composite request that tries to rename(2) the file |
|
|
236 | first. If rename files with "EXDEV", it creates the destination |
|
|
237 | file with mode 0200 and copies the contents of the source file |
|
|
238 | into it using "aio_sendfile", followed by restoring atime, |
|
|
239 | mtime, access mode and uid/gid, in that order, and unlinking the |
|
|
240 | $srcpath. |
|
|
241 | |
|
|
242 | If an error occurs, the partial destination file will be |
|
|
243 | unlinked, if possible, except when setting atime, mtime, access |
|
|
244 | mode and uid/gid, where errors are being ignored. |
|
|
245 | |
|
|
246 | aio_sendfile $out_fh, $in_fh, $in_offset, $length, |
|
|
247 | $callback->($retval) |
|
|
248 | Tries to copy $length bytes from $in_fh to $out_fh. It starts |
|
|
249 | reading at byte offset $in_offset, and starts writing at the |
|
|
250 | current file offset of $out_fh. Because of that, it is not safe |
|
|
251 | to issue more than one "aio_sendfile" per $out_fh, as they will |
|
|
252 | interfere with each other. |
|
|
253 | |
|
|
254 | This call tries to make use of a native "sendfile" syscall to |
|
|
255 | provide zero-copy operation. For this to work, $out_fh should |
|
|
256 | refer to a socket, and $in_fh should refer to mmap'able file. |
|
|
257 | |
|
|
258 | If the native sendfile call fails or is not implemented, it will |
|
|
259 | be emulated, so you can call "aio_sendfile" on any type of |
|
|
260 | filehandle regardless of the limitations of the operating |
|
|
261 | system. |
|
|
262 | |
|
|
263 | Please note, however, that "aio_sendfile" can read more bytes |
|
|
264 | from $in_fh than are written, and there is no way to find out |
|
|
265 | how many bytes have been read from "aio_sendfile" alone, as |
|
|
266 | "aio_sendfile" only provides the number of bytes written to |
|
|
267 | $out_fh. Only if the result value equals $length one can assume |
|
|
268 | that $length bytes have been read. |
|
|
269 | |
|
|
270 | aio_readahead $fh,$offset,$length, $callback->($retval) |
|
|
271 | "aio_readahead" populates the page cache with data from a file |
|
|
272 | so that subsequent reads from that file will not block on disk |
|
|
273 | I/O. The $offset argument specifies the starting point from |
|
|
274 | which data is to be read and $length specifies the number of |
|
|
275 | bytes to be read. I/O is performed in whole pages, so that |
|
|
276 | offset is effectively rounded down to a page boundary and bytes |
|
|
277 | are read up to the next page boundary greater than or equal to |
|
|
278 | (off-set+length). "aio_readahead" does not read beyond the end |
|
|
279 | of the file. The current file offset of the file is left |
|
|
280 | unchanged. |
|
|
281 | |
|
|
282 | If that syscall doesn't exist (likely if your OS isn't Linux) it |
|
|
283 | will be emulated by simply reading the data, which would have a |
|
|
284 | similar effect. |
|
|
285 | |
|
|
286 | aio_stat $fh_or_path, $callback->($status) |
|
|
287 | aio_lstat $fh, $callback->($status) |
|
|
288 | Works like perl's "stat" or "lstat" in void context. The |
|
|
289 | callback will be called after the stat and the results will be |
|
|
290 | available using "stat _" or "-s _" etc... |
|
|
291 | |
|
|
292 | The pathname passed to "aio_stat" must be absolute. See API |
|
|
293 | NOTES, above, for an explanation. |
|
|
294 | |
|
|
295 | Currently, the stats are always 64-bit-stats, i.e. instead of |
|
|
296 | returning an error when stat'ing a large file, the results will |
|
|
297 | be silently truncated unless perl itself is compiled with large |
|
|
298 | file support. |
|
|
299 | |
|
|
300 | Example: Print the length of /etc/passwd: |
|
|
301 | |
|
|
302 | aio_stat "/etc/passwd", sub { |
|
|
303 | $_[0] and die "stat failed: $!"; |
|
|
304 | print "size is ", -s _, "\n"; |
|
|
305 | }; |
|
|
306 | |
|
|
307 | aio_unlink $pathname, $callback->($status) |
|
|
308 | Asynchronously unlink (delete) a file and call the callback with |
|
|
309 | the result code. |
|
|
310 | |
|
|
311 | aio_link $srcpath, $dstpath, $callback->($status) |
|
|
312 | Asynchronously create a new link to the existing object at |
|
|
313 | $srcpath at the path $dstpath and call the callback with the |
|
|
314 | result code. |
|
|
315 | |
|
|
316 | aio_symlink $srcpath, $dstpath, $callback->($status) |
|
|
317 | Asynchronously create a new symbolic link to the existing object |
|
|
318 | at $srcpath at the path $dstpath and call the callback with the |
|
|
319 | result code. |
|
|
320 | |
|
|
321 | aio_rename $srcpath, $dstpath, $callback->($status) |
|
|
322 | Asynchronously rename the object at $srcpath to $dstpath, just |
|
|
323 | as rename(2) and call the callback with the result code. |
|
|
324 | |
|
|
325 | aio_rmdir $pathname, $callback->($status) |
|
|
326 | Asynchronously rmdir (delete) a directory and call the callback |
|
|
327 | with the result code. |
|
|
328 | |
|
|
329 | aio_readdir $pathname, $callback->($entries) |
|
|
330 | Unlike the POSIX call of the same name, "aio_readdir" reads an |
|
|
331 | entire directory (i.e. opendir + readdir + closedir). The |
|
|
332 | entries will not be sorted, and will NOT include the "." and |
|
|
333 | ".." entries. |
|
|
334 | |
|
|
335 | The callback a single argument which is either "undef" or an |
|
|
336 | array-ref with the filenames. |
|
|
337 | |
|
|
338 | aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) |
|
|
339 | Scans a directory (similar to "aio_readdir") but additionally |
|
|
340 | tries to efficiently separate the entries of directory $path |
|
|
341 | into two sets of names, directories you can recurse into |
|
|
342 | (directories), and ones you cannot recurse into (everything |
|
|
343 | else, including symlinks to directories). |
|
|
344 | |
|
|
345 | "aio_scandir" is a composite request that creates of many sub |
|
|
346 | requests_ $maxreq specifies the maximum number of outstanding |
|
|
347 | aio requests that this function generates. If it is "<= 0", then |
|
|
348 | a suitable default will be chosen (currently 6). |
|
|
349 | |
|
|
350 | On error, the callback is called without arguments, otherwise it |
|
|
351 | receives two array-refs with path-relative entry names. |
|
|
352 | |
|
|
353 | Example: |
|
|
354 | |
|
|
355 | aio_scandir $dir, 0, sub { |
|
|
356 | my ($dirs, $nondirs) = @_; |
|
|
357 | print "real directories: @$dirs\n"; |
|
|
358 | print "everything else: @$nondirs\n"; |
|
|
359 | }; |
|
|
360 | |
|
|
361 | Implementation notes. |
|
|
362 | |
|
|
363 | The "aio_readdir" cannot be avoided, but "stat()"'ing every |
|
|
364 | entry can. |
|
|
365 | |
|
|
366 | After reading the directory, the modification time, size etc. of |
|
|
367 | the directory before and after the readdir is checked, and if |
|
|
368 | they match (and isn't the current time), the link count will be |
|
|
369 | used to decide how many entries are directories (if >= 2). |
|
|
370 | Otherwise, no knowledge of the number of subdirectories will be |
|
|
371 | assumed. |
|
|
372 | |
|
|
373 | Then entries will be sorted into likely directories (everything |
|
|
374 | without a non-initial dot currently) and likely non-directories |
|
|
375 | (everything else). Then every entry plus an appended "/." will |
|
|
376 | be "stat"'ed, likely directories first. If that succeeds, it |
|
|
377 | assumes that the entry is a directory or a symlink to directory |
|
|
378 | (which will be checked seperately). This is often faster than |
|
|
379 | stat'ing the entry itself because filesystems might detect the |
|
|
380 | type of the entry without reading the inode data (e.g. ext2fs |
|
|
381 | filetype feature). |
|
|
382 | |
|
|
383 | If the known number of directories (link count - 2) has been |
|
|
384 | reached, the rest of the entries is assumed to be |
|
|
385 | non-directories. |
|
|
386 | |
|
|
387 | This only works with certainty on POSIX (= UNIX) filesystems, |
|
|
388 | which fortunately are the vast majority of filesystems around. |
|
|
389 | |
|
|
390 | It will also likely work on non-POSIX filesystems with reduced |
|
|
391 | efficiency as those tend to return 0 or 1 as link counts, which |
|
|
392 | disables the directory counting heuristic. |
|
|
393 | |
|
|
394 | aio_fsync $fh, $callback->($status) |
|
|
395 | Asynchronously call fsync on the given filehandle and call the |
|
|
396 | callback with the fsync result code. |
|
|
397 | |
|
|
398 | aio_fdatasync $fh, $callback->($status) |
|
|
399 | Asynchronously call fdatasync on the given filehandle and call |
|
|
400 | the callback with the fdatasync result code. |
|
|
401 | |
|
|
402 | If this call isn't available because your OS lacks it or it |
|
|
403 | couldn't be detected, it will be emulated by calling "fsync" |
|
|
404 | instead. |
|
|
405 | |
|
|
406 | aio_group $callback->(...) |
|
|
407 | This is a very special aio request: Instead of doing something, |
|
|
408 | it is a container for other aio requests, which is useful if you |
|
|
409 | want to bundle many requests into a single, composite, request |
|
|
410 | with a definite callback and the ability to cancel the whole |
|
|
411 | request with its subrequests. |
|
|
412 | |
|
|
413 | Returns an object of class IO::AIO::GRP. See its documentation |
|
|
414 | below for more info. |
|
|
415 | |
|
|
416 | Example: |
|
|
417 | |
|
|
418 | my $grp = aio_group sub { |
|
|
419 | print "all stats done\n"; |
|
|
420 | }; |
|
|
421 | |
|
|
422 | add $grp |
|
|
423 | (aio_stat ...), |
|
|
424 | (aio_stat ...), |
|
|
425 | ...; |
|
|
426 | |
|
|
427 | aio_nop $callback->() |
|
|
428 | This is a special request - it does nothing in itself and is |
|
|
429 | only used for side effects, such as when you want to add a dummy |
|
|
430 | request to a group so that finishing the requests in the group |
|
|
431 | depends on executing the given code. |
|
|
432 | |
|
|
433 | While this request does nothing, it still goes through the |
|
|
434 | execution phase and still requires a worker thread. Thus, the |
|
|
435 | callback will not be executed immediately but only after other |
|
|
436 | requests in the queue have entered their execution phase. This |
|
|
437 | can be used to measure request latency. |
|
|
438 | |
|
|
439 | IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED* |
|
|
440 | Mainly used for debugging and benchmarking, this aio request |
|
|
441 | puts one of the request workers to sleep for the given time. |
|
|
442 | |
|
|
443 | While it is theoretically handy to have simple I/O scheduling |
|
|
444 | requests like sleep and file handle readable/writable, the |
|
|
445 | overhead this creates is immense (it blocks a thread for a long |
|
|
446 | time) so do not use this function except to put your application |
|
|
447 | under artificial I/O pressure. |
|
|
448 | |
|
|
449 | IO::AIO::REQ CLASS |
|
|
450 | All non-aggregate "aio_*" functions return an object of this class |
|
|
451 | when called in non-void context. |
|
|
452 | |
|
|
453 | cancel $req |
|
|
454 | Cancels the request, if possible. Has the effect of skipping |
|
|
455 | execution when entering the execute state and skipping calling |
|
|
456 | the callback when entering the the result state, but will leave |
|
|
457 | the request otherwise untouched. That means that requests that |
|
|
458 | currently execute will not be stopped and resources held by the |
|
|
459 | request will not be freed prematurely. |
|
|
460 | |
|
|
461 | cb $req $callback->(...) |
|
|
462 | Replace (or simply set) the callback registered to the request. |
|
|
463 | |
|
|
464 | IO::AIO::GRP CLASS |
|
|
465 | This class is a subclass of IO::AIO::REQ, so all its methods apply |
|
|
466 | to objects of this class, too. |
|
|
467 | |
|
|
468 | A IO::AIO::GRP object is a special request that can contain multiple |
|
|
469 | other aio requests. |
|
|
470 | |
|
|
471 | You create one by calling the "aio_group" constructing function with |
|
|
472 | a callback that will be called when all contained requests have |
|
|
473 | entered the "done" state: |
|
|
474 | |
|
|
475 | my $grp = aio_group sub { |
|
|
476 | print "all requests are done\n"; |
89 | }; |
477 | }; |
90 | |
478 | |
91 | aio_close $fh, $callback |
479 | You add requests by calling the "add" method with one or more |
92 | Asynchronously close a file and call the callback with the result |
480 | "IO::AIO::REQ" objects: |
93 | code. *WARNING:* although accepted, you should not pass in a perl |
|
|
94 | filehandle here, as perl will likely close the file descriptor |
|
|
95 | itself when the filehandle is destroyed. Normally, you can safely |
|
|
96 | call perls "close" or just let filehandles go out of scope. |
|
|
97 | |
481 | |
98 | aio_read $fh,$offset,$length, $data,$dataoffset,$callback |
482 | $grp->add (aio_unlink "..."); |
99 | aio_write $fh,$offset,$length, $data,$dataoffset,$callback |
|
|
100 | Reads or writes "length" bytes from the specified "fh" and "offset" |
|
|
101 | into the scalar given by "data" and offset "dataoffset" and calls |
|
|
102 | the callback without the actual number of bytes read (or -1 on |
|
|
103 | error, just like the syscall). |
|
|
104 | |
483 | |
105 | Example: Read 15 bytes at offset 7 into scalar $buffer, starting at |
484 | add $grp aio_stat "...", sub { |
106 | offset 0 within the scalar: |
485 | $_[0] or return $grp->result ("error"); |
107 | |
486 | |
108 | aio_read $fh, 7, 15, $buffer, 0, sub { |
487 | # add another request dynamically, if first succeeded |
109 | $_[0] > 0 or die "read error: $!"; |
488 | add $grp aio_open "...", sub { |
110 | print "read $_[0] bytes: <$buffer>\n"; |
489 | $grp->result ("ok"); |
|
|
490 | }; |
111 | }; |
491 | }; |
112 | |
492 | |
113 | aio_readahead $fh,$offset,$length, $callback |
493 | This makes it very easy to create composite requests (see the source |
114 | Asynchronously reads the specified byte range into the page cache, |
494 | of "aio_move" for an application) that work and feel like simple |
115 | using the "readahead" syscall. If that syscall doesn't exist (likely |
495 | requests. |
116 | if your OS isn't Linux) the status will be -1 and $! is set to |
|
|
117 | ENOSYS. |
|
|
118 | |
496 | |
119 | readahead() populates the page cache with data from a file so that |
497 | * The IO::AIO::GRP objects will be cleaned up during calls to |
120 | subsequent reads from that file will not block on disk I/O. The |
498 | "IO::AIO::poll_cb", just like any other request. |
121 | $offset argument specifies the starting point from which data is to |
499 | * They can be canceled like any other request. Canceling will cancel |
122 | be read and $length specifies the number of bytes to be read. I/O is |
500 | not only the request itself, but also all requests it contains. |
123 | performed in whole pages, so that offset is effectively rounded down |
501 | * They can also can also be added to other IO::AIO::GRP objects. |
124 | to a page boundary and bytes are read up to the next page boundary |
502 | * You must not add requests to a group from within the group |
125 | greater than or equal to (off-set+length). aio_readahead() does not |
503 | callback (or any later time). |
126 | read beyond the end of the file. The current file offset of the file |
|
|
127 | is left unchanged. |
|
|
128 | |
504 | |
129 | aio_stat $fh_or_path, $callback |
505 | Their lifetime, simplified, looks like this: when they are empty, |
130 | aio_lstat $fh, $callback |
506 | they will finish very quickly. If they contain only requests that |
131 | Works like perl's "stat" or "lstat" in void context. The callback |
507 | are in the "done" state, they will also finish. Otherwise they will |
132 | will be called after the stat and the results will be available |
508 | continue to exist. |
133 | using "stat _" or "-s _" etc... |
|
|
134 | |
509 | |
135 | The pathname passed to "aio_stat" must be absolute. See API NOTES, |
510 | That means after creating a group you have some time to add |
136 | above, for an explanation. |
511 | requests. And in the callbacks of those requests, you can add |
|
|
512 | further requests to the group. And only when all those requests have |
|
|
513 | finished will the the group itself finish. |
137 | |
514 | |
138 | Currently, the stats are always 64-bit-stats, i.e. instead of |
515 | add $grp ... |
139 | returning an error when stat'ing a large file, the results will be |
516 | $grp->add (...) |
140 | silently truncated unless perl itself is compiled with large file |
517 | Add one or more requests to the group. Any type of IO::AIO::REQ |
141 | support. |
518 | can be added, including other groups, as long as you do not |
|
|
519 | create circular dependencies. |
142 | |
520 | |
143 | Example: Print the length of /etc/passwd: |
521 | Returns all its arguments. |
144 | |
522 | |
145 | aio_stat "/etc/passwd", sub { |
523 | $grp->cancel_subs |
146 | $_[0] and die "stat failed: $!"; |
524 | Cancel all subrequests and clears any feeder, but not the group |
147 | print "size is ", -s _, "\n"; |
525 | request itself. Useful when you queued a lot of events but got a |
|
|
526 | result early. |
|
|
527 | |
|
|
528 | $grp->result (...) |
|
|
529 | Set the result value(s) that will be passed to the group |
|
|
530 | callback when all subrequests have finished and set thre groups |
|
|
531 | errno to the current value of errno (just like calling "errno" |
|
|
532 | without an error number). By default, no argument will be passed |
|
|
533 | and errno is zero. |
|
|
534 | |
|
|
535 | $grp->errno ([$errno]) |
|
|
536 | Sets the group errno value to $errno, or the current value of |
|
|
537 | errno when the argument is missing. |
|
|
538 | |
|
|
539 | Every aio request has an associated errno value that is restored |
|
|
540 | when the callback is invoked. This method lets you change this |
|
|
541 | value from its default (0). |
|
|
542 | |
|
|
543 | Calling "result" will also set errno, so make sure you either |
|
|
544 | set $! before the call to "result", or call c<errno> after it. |
|
|
545 | |
|
|
546 | feed $grp $callback->($grp) |
|
|
547 | Sets a feeder/generator on this group: every group can have an |
|
|
548 | attached generator that generates requests if idle. The idea |
|
|
549 | behind this is that, although you could just queue as many |
|
|
550 | requests as you want in a group, this might starve other |
|
|
551 | requests for a potentially long time. For example, "aio_scandir" |
|
|
552 | might generate hundreds of thousands "aio_stat" requests, |
|
|
553 | delaying any later requests for a long time. |
|
|
554 | |
|
|
555 | To avoid this, and allow incremental generation of requests, you |
|
|
556 | can instead a group and set a feeder on it that generates those |
|
|
557 | requests. The feed callback will be called whenever there are |
|
|
558 | few enough (see "limit", below) requests active in the group |
|
|
559 | itself and is expected to queue more requests. |
|
|
560 | |
|
|
561 | The feed callback can queue as many requests as it likes (i.e. |
|
|
562 | "add" does not impose any limits). |
|
|
563 | |
|
|
564 | If the feed does not queue more requests when called, it will be |
|
|
565 | automatically removed from the group. |
|
|
566 | |
|
|
567 | If the feed limit is 0, it will be set to 2 automatically. |
|
|
568 | |
|
|
569 | Example: |
|
|
570 | |
|
|
571 | # stat all files in @files, but only ever use four aio requests concurrently: |
|
|
572 | |
|
|
573 | my $grp = aio_group sub { print "finished\n" }; |
|
|
574 | limit $grp 4; |
|
|
575 | feed $grp sub { |
|
|
576 | my $file = pop @files |
|
|
577 | or return; |
|
|
578 | |
|
|
579 | add $grp aio_stat $file, sub { ... }; |
148 | }; |
580 | }; |
149 | |
581 | |
150 | aio_unlink $pathname, $callback |
582 | limit $grp $num |
151 | Asynchronously unlink (delete) a file and call the callback with the |
583 | Sets the feeder limit for the group: The feeder will be called |
152 | result code. |
584 | whenever the group contains less than this many requests. |
153 | |
585 | |
154 | aio_fsync $fh, $callback |
586 | Setting the limit to 0 will pause the feeding process. |
155 | Asynchronously call fsync on the given filehandle and call the |
|
|
156 | callback with the fsync result code. |
|
|
157 | |
|
|
158 | aio_fdatasync $fh, $callback |
|
|
159 | Asynchronously call fdatasync on the given filehandle and call the |
|
|
160 | callback with the fdatasync result code. |
|
|
161 | |
587 | |
162 | SUPPORT FUNCTIONS |
588 | SUPPORT FUNCTIONS |
163 | $fileno = IO::AIO::poll_fileno |
589 | $fileno = IO::AIO::poll_fileno |
164 | Return the *request result pipe filehandle*. This filehandle must be |
590 | Return the *request result pipe file descriptor*. This |
165 | polled for reading by some mechanism outside this module (e.g. Event |
591 | filehandle must be polled for reading by some mechanism outside |
166 | or select, see below). If the pipe becomes readable you have to call |
592 | this module (e.g. Event or select, see below or the SYNOPSIS). |
167 | "poll_cb" to check the results. |
593 | If the pipe becomes readable you have to call "poll_cb" to check |
|
|
594 | the results. |
168 | |
595 | |
169 | See "poll_cb" for an example. |
596 | See "poll_cb" for an example. |
170 | |
597 | |
171 | IO::AIO::poll_cb |
598 | IO::AIO::poll_cb |
172 | Process all outstanding events on the result pipe. You have to call |
599 | Process all outstanding events on the result pipe. You have to |
173 | this regularly. Returns the number of events processed. Returns |
600 | call this regularly. Returns the number of events processed. |
174 | immediately when no events are outstanding. |
601 | Returns immediately when no events are outstanding. |
175 | |
602 | |
176 | You can use Event to multiplex, e.g.: |
603 | If not all requests were processed for whatever reason, the |
|
|
604 | filehandle will still be ready when "poll_cb" returns. |
177 | |
605 | |
|
|
606 | Example: Install an Event watcher that automatically calls |
|
|
607 | IO::AIO::poll_cb with high priority: |
|
|
608 | |
178 | Event->io (fd => IO::AIO::poll_fileno, |
609 | Event->io (fd => IO::AIO::poll_fileno, |
179 | poll => 'r', async => 1, |
610 | poll => 'r', async => 1, |
180 | cb => \&IO::AIO::poll_cb); |
611 | cb => \&IO::AIO::poll_cb); |
181 | |
612 | |
|
|
613 | IO::AIO::poll_some $max_requests |
|
|
614 | Similar to "poll_cb", but only processes up to $max_requests |
|
|
615 | requests at a time. |
|
|
616 | |
|
|
617 | Useful if you want to ensure some level of interactiveness when |
|
|
618 | perl is not fast enough to process all requests in time. |
|
|
619 | |
|
|
620 | Example: Install an Event watcher that automatically calls |
|
|
621 | IO::AIO::poll_some with low priority, to ensure that other parts |
|
|
622 | of the program get the CPU sometimes even under high AIO load. |
|
|
623 | |
|
|
624 | Event->io (fd => IO::AIO::poll_fileno, |
|
|
625 | poll => 'r', nice => 1, |
|
|
626 | cb => sub { IO::AIO::poll_some 256 }); |
|
|
627 | |
182 | IO::AIO::poll_wait |
628 | IO::AIO::poll_wait |
183 | Wait till the result filehandle becomes ready for reading (simply |
629 | Wait till the result filehandle becomes ready for reading |
184 | does a select on the filehandle. This is useful if you want to |
630 | (simply does a "select" on the filehandle. This is useful if you |
185 | synchronously wait for some requests to finish). |
631 | want to synchronously wait for some requests to finish). |
186 | |
632 | |
187 | See "nreqs" for an example. |
633 | See "nreqs" for an example. |
188 | |
634 | |
189 | IO::AIO::nreqs |
635 | IO::AIO::nreqs |
190 | Returns the number of requests currently outstanding. |
636 | Returns the number of requests currently in the ready, execute |
|
|
637 | or pending states (i.e. for which their callback has not been |
|
|
638 | invoked yet). |
191 | |
639 | |
192 | Example: wait till there are no outstanding requests anymore: |
640 | Example: wait till there are no outstanding requests anymore: |
193 | |
641 | |
194 | IO::AIO::poll_wait, IO::AIO::poll_cb |
642 | IO::AIO::poll_wait, IO::AIO::poll_cb |
195 | while IO::AIO::nreqs; |
643 | while IO::AIO::nreqs; |
196 | |
644 | |
|
|
645 | IO::AIO::nready |
|
|
646 | Returns the number of requests currently in the ready state (not |
|
|
647 | yet executed). |
|
|
648 | |
|
|
649 | IO::AIO::npending |
|
|
650 | Returns the number of requests currently in the pending state |
|
|
651 | (executed, but not yet processed by poll_cb). |
|
|
652 | |
197 | IO::AIO::flush |
653 | IO::AIO::flush |
198 | Wait till all outstanding AIO requests have been handled. |
654 | Wait till all outstanding AIO requests have been handled. |
199 | |
655 | |
200 | Strictly equivalent to: |
656 | Strictly equivalent to: |
201 | |
657 | |
202 | IO::AIO::poll_wait, IO::AIO::poll_cb |
658 | IO::AIO::poll_wait, IO::AIO::poll_cb |
203 | while IO::AIO::nreqs; |
659 | while IO::AIO::nreqs; |
204 | |
660 | |
205 | IO::AIO::poll |
661 | IO::AIO::poll |
206 | Waits until some requests have been handled. |
662 | Waits until some requests have been handled. |
207 | |
663 | |
208 | Strictly equivalent to: |
664 | Strictly equivalent to: |
209 | |
665 | |
210 | IO::AIO::poll_wait, IO::AIO::poll_cb |
666 | IO::AIO::poll_wait, IO::AIO::poll_cb |
211 | if IO::AIO::nreqs; |
667 | if IO::AIO::nreqs; |
212 | |
668 | |
213 | IO::AIO::min_parallel $nthreads |
669 | IO::AIO::min_parallel $nthreads |
214 | Set the minimum number of AIO threads to $nthreads. The default is |
670 | Set the minimum number of AIO threads to $nthreads. The current |
215 | 1, which means a single asynchronous operation can be done at one |
671 | default is 8, which means eight asynchronous operations can |
216 | time (the number of outstanding operations, however, is unlimited). |
672 | execute concurrently at any one time (the number of outstanding |
|
|
673 | requests, however, is unlimited). |
217 | |
674 | |
|
|
675 | IO::AIO starts threads only on demand, when an AIO request is |
|
|
676 | queued and no free thread exists. |
|
|
677 | |
218 | It is recommended to keep the number of threads low, as some Linux |
678 | It is recommended to keep the number of threads relatively low, |
219 | kernel versions will scale negatively with the number of threads |
679 | as some Linux kernel versions will scale negatively with the |
220 | (higher parallelity => MUCH higher latency). With current Linux 2.6 |
680 | number of threads (higher parallelity => MUCH higher latency). |
221 | versions, 4-32 threads should be fine. |
681 | With current Linux 2.6 versions, 4-32 threads should be fine. |
222 | |
682 | |
223 | Under normal circumstances you don't need to call this function, as |
683 | Under most circumstances you don't need to call this function, |
224 | this module automatically starts some threads (the exact number |
684 | as the module selects a default that is suitable for low to |
225 | might change, and is currently 4). |
685 | moderate load. |
226 | |
686 | |
227 | IO::AIO::max_parallel $nthreads |
687 | IO::AIO::max_parallel $nthreads |
228 | Sets the maximum number of AIO threads to $nthreads. If more than |
688 | Sets the maximum number of AIO threads to $nthreads. If more |
229 | the specified number of threads are currently running, kill them. |
689 | than the specified number of threads are currently running, this |
230 | This function blocks until the limit is reached. |
690 | function kills them. This function blocks until the limit is |
|
|
691 | reached. |
231 | |
692 | |
|
|
693 | While $nthreads are zero, aio requests get queued but not |
|
|
694 | executed until the number of threads has been increased again. |
|
|
695 | |
232 | This module automatically runs "max_parallel 0" at program end, to |
696 | This module automatically runs "max_parallel 0" at program end, |
233 | ensure that all threads are killed and that there are no outstanding |
697 | to ensure that all threads are killed and that there are no |
234 | requests. |
698 | outstanding requests. |
235 | |
699 | |
236 | Under normal circumstances you don't need to call this function. |
700 | Under normal circumstances you don't need to call this function. |
237 | |
701 | |
238 | $oldnreqs = IO::AIO::max_outstanding $nreqs |
702 | $oldmaxreqs = IO::AIO::max_outstanding $maxreqs |
|
|
703 | This is a very bad function to use in interactive programs |
|
|
704 | because it blocks, and a bad way to reduce concurrency because |
|
|
705 | it is inexact: Better use an "aio_group" together with a feed |
|
|
706 | callback. |
|
|
707 | |
239 | Sets the maximum number of outstanding requests to $nreqs. If you |
708 | Sets the maximum number of outstanding requests to $nreqs. If |
240 | try to queue up more than this number of requests, the caller will |
709 | you to queue up more than this number of requests, the next call |
241 | block until some requests have been handled. |
710 | to the "poll_cb" (and "poll_some" and other functions calling |
|
|
711 | "poll_cb") function will block until the limit is no longer |
|
|
712 | exceeded. |
242 | |
713 | |
243 | The default is very large, so normally there is no practical limit. |
714 | The default value is very large, so there is no practical limit |
244 | If you queue up many requests in a loop it it often improves speed |
715 | on the number of outstanding requests. |
245 | if you set this to a relatively low number, such as 100. |
|
|
246 | |
716 | |
247 | Under normal circumstances you don't need to call this function. |
717 | You can still queue as many requests as you want. Therefore, |
|
|
718 | "max_oustsanding" is mainly useful in simple scripts (with low |
|
|
719 | values) or as a stop gap to shield against fatal memory overflow |
|
|
720 | (with large values). |
|
|
721 | |
|
|
722 | FORK BEHAVIOUR |
|
|
723 | This module should do "the right thing" when the process using it |
|
|
724 | forks: |
|
|
725 | |
|
|
726 | Before the fork, IO::AIO enters a quiescent state where no requests |
|
|
727 | can be added in other threads and no results will be processed. |
|
|
728 | After the fork the parent simply leaves the quiescent state and |
|
|
729 | continues request/result processing, while the child frees the |
|
|
730 | request/result queue (so that the requests started before the fork |
|
|
731 | will only be handled in the parent). Threads will be started on |
|
|
732 | demand until the limit set in the parent process has been reached |
|
|
733 | again. |
|
|
734 | |
|
|
735 | In short: the parent will, after a short pause, continue as if fork |
|
|
736 | had not been called, while the child will act as if IO::AIO has not |
|
|
737 | been used yet. |
|
|
738 | |
|
|
739 | MEMORY USAGE |
|
|
740 | Per-request usage: |
|
|
741 | |
|
|
742 | Each aio request uses - depending on your architecture - around |
|
|
743 | 100-200 bytes of memory. In addition, stat requests need a stat |
|
|
744 | buffer (possibly a few hundred bytes), readdir requires a result |
|
|
745 | buffer and so on. Perl scalars and other data passed into aio |
|
|
746 | requests will also be locked and will consume memory till the |
|
|
747 | request has entered the done state. |
|
|
748 | |
|
|
749 | This is now awfully much, so queuing lots of requests is not usually |
|
|
750 | a problem. |
|
|
751 | |
|
|
752 | Per-thread usage: |
|
|
753 | |
|
|
754 | In the execution phase, some aio requests require more memory for |
|
|
755 | temporary buffers, and each thread requires a stack and other data |
|
|
756 | structures (usually around 16k-128k, depending on the OS). |
|
|
757 | |
|
|
758 | KNOWN BUGS |
|
|
759 | Known bugs will be fixed in the next release. |
248 | |
760 | |
249 | SEE ALSO |
761 | SEE ALSO |
250 | Coro, Linux::AIO. |
762 | Coro::AIO. |
251 | |
763 | |
252 | AUTHOR |
764 | AUTHOR |
253 | Marc Lehmann <schmorp@schmorp.de> |
765 | Marc Lehmann <schmorp@schmorp.de> |
254 | http://home.schmorp.de/ |
766 | http://home.schmorp.de/ |
255 | |
767 | |