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61 | faster on a RAID volume or over NFS when you do a number of stat |
61 | faster on a RAID volume or over NFS when you do a number of stat |
62 | operations concurrently. |
62 | operations concurrently. |
63 | |
63 | |
64 | While most of this works on all types of file descriptors (for example |
64 | While most of this works on all types of file descriptors (for example |
65 | sockets), using these functions on file descriptors that support |
65 | sockets), using these functions on file descriptors that support |
66 | nonblocking operation (again, sockets, pipes etc.) is very inefficient |
66 | nonblocking operation (again, sockets, pipes etc.) is very inefficient. |
67 | or might not work (aio_read fails on sockets/pipes/fifos). Use an event |
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68 | loop for that (such as the Event module): IO::AIO will naturally fit |
67 | Use an event loop for that (such as the Event module): IO::AIO will |
69 | into such an event loop itself. |
68 | naturally fit into such an event loop itself. |
70 | |
69 | |
71 | In this version, a number of threads are started that execute your |
70 | In this version, a number of threads are started that execute your |
72 | requests and signal their completion. You don't need thread support in |
71 | requests and signal their completion. You don't need thread support in |
73 | perl, and the threads created by this module will not be visible to |
72 | perl, and the threads created by this module will not be visible to |
74 | perl. In the future, this module might make use of the native aio |
73 | perl. In the future, this module might make use of the native aio |
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76 | not well-supported or restricted (GNU/Linux doesn't allow them on normal |
75 | not well-supported or restricted (GNU/Linux doesn't allow them on normal |
77 | files currently, for example), and they would only support aio_read and |
76 | files currently, for example), and they would only support aio_read and |
78 | aio_write, so the remaining functionality would have to be implemented |
77 | aio_write, so the remaining functionality would have to be implemented |
79 | using threads anyway. |
78 | using threads anyway. |
80 | |
79 | |
81 | Although the module will work with in the presence of other (Perl-) |
80 | Although the module will work in the presence of other (Perl-) threads, |
82 | threads, it is currently not reentrant in any way, so use appropriate |
81 | it is currently not reentrant in any way, so use appropriate locking |
83 | locking yourself, always call "poll_cb" from within the same thread, or |
82 | yourself, always call "poll_cb" from within the same thread, or never |
84 | never call "poll_cb" (or other "aio_" functions) recursively. |
83 | call "poll_cb" (or other "aio_" functions) recursively. |
85 | |
84 | |
86 | EXAMPLE |
85 | EXAMPLE |
87 | This is a simple example that uses the Event module and loads |
86 | This is a simple example that uses the Event module and loads |
88 | /etc/passwd asynchronously: |
87 | /etc/passwd asynchronously: |
89 | |
88 | |
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269 | This is supposed to be a bug in the API, so that might change. It's |
268 | This is supposed to be a bug in the API, so that might change. It's |
270 | therefore best to avoid this function. |
269 | therefore best to avoid this function. |
271 | |
270 | |
272 | aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) |
271 | aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) |
273 | aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) |
272 | aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) |
274 | Reads or writes "length" bytes from the specified "fh" and "offset" |
273 | Reads or writes $length bytes from the specified $fh and $offset |
275 | into the scalar given by "data" and offset "dataoffset" and calls |
274 | into the scalar given by $data and offset $dataoffset and calls the |
276 | the callback without the actual number of bytes read (or -1 on |
275 | callback without the actual number of bytes read (or -1 on error, |
277 | error, just like the syscall). |
276 | just like the syscall). |
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277 | |
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278 | If $offset is undefined, then the current file descriptor offset |
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279 | will be used (and updated), otherwise the file descriptor offset |
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280 | will not be changed by these calls. |
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281 | |
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282 | If $length is undefined in "aio_write", use the remaining length of |
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283 | $data. |
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284 | |
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285 | If $dataoffset is less than zero, it will be counted from the end of |
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286 | $data. |
278 | |
287 | |
279 | The $data scalar *MUST NOT* be modified in any way while the request |
288 | The $data scalar *MUST NOT* be modified in any way while the request |
280 | is outstanding. Modifying it can result in segfaults or WW3 (if the |
289 | is outstanding. Modifying it can result in segfaults or World War |
281 | necessary/optional hardware is installed). |
290 | III (if the necessary/optional hardware is installed). |
282 | |
291 | |
283 | Example: Read 15 bytes at offset 7 into scalar $buffer, starting at |
292 | Example: Read 15 bytes at offset 7 into scalar $buffer, starting at |
284 | offset 0 within the scalar: |
293 | offset 0 within the scalar: |
285 | |
294 | |
286 | aio_read $fh, 7, 15, $buffer, 0, sub { |
295 | aio_read $fh, 7, 15, $buffer, 0, sub { |
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344 | aio_stat "/etc/passwd", sub { |
353 | aio_stat "/etc/passwd", sub { |
345 | $_[0] and die "stat failed: $!"; |
354 | $_[0] and die "stat failed: $!"; |
346 | print "size is ", -s _, "\n"; |
355 | print "size is ", -s _, "\n"; |
347 | }; |
356 | }; |
348 | |
357 | |
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358 | aio_utime $fh_or_path, $atime, $mtime, $callback->($status) |
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359 | Works like perl's "utime" function (including the special case of |
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360 | $atime and $mtime being undef). Fractional times are supported if |
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361 | the underlying syscalls support them. |
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362 | |
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363 | When called with a pathname, uses utimes(2) if available, otherwise |
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364 | utime(2). If called on a file descriptor, uses futimes(2) if |
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365 | available, otherwise returns ENOSYS, so this is not portable. |
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366 | |
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367 | Examples: |
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368 | |
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369 | # set atime and mtime to current time (basically touch(1)): |
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370 | aio_utime "path", undef, undef; |
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371 | # set atime to current time and mtime to beginning of the epoch: |
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372 | aio_utime "path", time, undef; # undef==0 |
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373 | |
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374 | aio_chown $fh_or_path, $uid, $gid, $callback->($status) |
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375 | Works like perl's "chown" function, except that "undef" for either |
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376 | $uid or $gid is being interpreted as "do not change" (but -1 can |
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377 | also be used). |
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378 | |
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379 | Examples: |
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380 | |
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381 | # same as "chown root path" in the shell: |
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382 | aio_chown "path", 0, -1; |
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383 | # same as above: |
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384 | aio_chown "path", 0, undef; |
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385 | |
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386 | aio_truncate $fh_or_path, $offset, $callback->($status) |
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387 | Works like truncate(2) or ftruncate(2). |
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388 | |
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389 | aio_chmod $fh_or_path, $mode, $callback->($status) |
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390 | Works like perl's "chmod" function. |
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391 | |
349 | aio_unlink $pathname, $callback->($status) |
392 | aio_unlink $pathname, $callback->($status) |
350 | Asynchronously unlink (delete) a file and call the callback with the |
393 | Asynchronously unlink (delete) a file and call the callback with the |
351 | result code. |
394 | result code. |
352 | |
395 | |
353 | aio_mknod $path, $mode, $dev, $callback->($status) |
396 | aio_mknod $path, $mode, $dev, $callback->($status) |
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808 | $oldmaxreqs = IO::AIO::max_outstanding $maxreqs |
851 | $oldmaxreqs = IO::AIO::max_outstanding $maxreqs |
809 | This is a very bad function to use in interactive programs because |
852 | This is a very bad function to use in interactive programs because |
810 | it blocks, and a bad way to reduce concurrency because it is |
853 | it blocks, and a bad way to reduce concurrency because it is |
811 | inexact: Better use an "aio_group" together with a feed callback. |
854 | inexact: Better use an "aio_group" together with a feed callback. |
812 | |
855 | |
813 | Sets the maximum number of outstanding requests to $nreqs. If you to |
856 | Sets the maximum number of outstanding requests to $nreqs. If you do |
814 | queue up more than this number of requests, the next call to the |
857 | queue up more than this number of requests, the next call to the |
815 | "poll_cb" (and "poll_some" and other functions calling "poll_cb") |
858 | "poll_cb" (and "poll_some" and other functions calling "poll_cb") |
816 | function will block until the limit is no longer exceeded. |
859 | function will block until the limit is no longer exceeded. |
817 | |
860 | |
818 | The default value is very large, so there is no practical limit on |
861 | The default value is very large, so there is no practical limit on |
… | |
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864 | bytes of memory. In addition, stat requests need a stat buffer (possibly |
907 | bytes of memory. In addition, stat requests need a stat buffer (possibly |
865 | a few hundred bytes), readdir requires a result buffer and so on. Perl |
908 | a few hundred bytes), readdir requires a result buffer and so on. Perl |
866 | scalars and other data passed into aio requests will also be locked and |
909 | scalars and other data passed into aio requests will also be locked and |
867 | will consume memory till the request has entered the done state. |
910 | will consume memory till the request has entered the done state. |
868 | |
911 | |
869 | This is now awfully much, so queuing lots of requests is not usually a |
912 | This is not awfully much, so queuing lots of requests is not usually a |
870 | problem. |
913 | problem. |
871 | |
914 | |
872 | Per-thread usage: |
915 | Per-thread usage: |
873 | |
916 | |
874 | In the execution phase, some aio requests require more memory for |
917 | In the execution phase, some aio requests require more memory for |