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1.1 |
NAME |
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Linux::AIO - linux-specific aio implemented using clone |
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SYNOPSIS |
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use Linux::AIO; |
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DESCRIPTION |
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1.3 |
This module implements asynchronous I/O using the means available to |
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Linux - clone. It does not hook into the POSIX aio_* functions because |
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Linux does not yet support these in the kernel (even as of 2.6.12, only |
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O_DIRECT files are supported) and even if, it would only allow aio_read |
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and write, not open, stat and so on. |
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1.1 |
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Instead, in this module a number of (non-posix) threads are started that |
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execute your read/writes and signal their completion. You don't need |
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thread support in your libc or perl, and the threads created by this |
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module will not be visible to the pthreads library. |
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NOTICE: the threads created by this module will automatically be killed |
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when the thread calling min_parallel exits. Make sure you only ever call |
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min_parallel from the same thread that loaded this module. |
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1.3 |
Although the module will work with in the presence of other threads, it |
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is not reentrant, so use appropriate locking yourself. |
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1.1 |
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Linux::AIO::min_parallel $nthreads |
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Set the minimum number of AIO threads to $nthreads. The default is |
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1, which means a single asynchronous operation can be done at one |
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time (the number of outstanding operations, however, is unlimited). |
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1.2 |
It is recommended to keep the number of threads low, as some linux |
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1.1 |
kernel versions will scale negatively with the number of threads |
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(higher parallelity => MUCH higher latency). |
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1.2 |
Linux::AIO::max_parallel $nthreads |
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Sets the maximum number of AIO threads to $nthreads. If more than |
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the specified number of threads are currently running, kill them. |
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This function blocks until the limit is reached. |
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This module automatically runs "max_parallel 0" at program end, to |
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ensure that all threads are killed and that there are no outstanding |
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requests. |
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1.1 |
$fileno = Linux::AIO::poll_fileno |
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Return the *request result pipe filehandle*. This filehandle must be |
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polled for reading by some mechanism outside this module (e.g. Event |
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or select, see below). If the pipe becomes readable you have to call |
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"poll_cb" to check the results. |
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Linux::AIO::poll_cb |
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Process all outstanding events on the result pipe. You have to call |
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this regularly. Returns the number of events processed. Returns |
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immediately when no events are outstanding. |
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You can use Event to multiplex, e.g.: |
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Event->io (fd => Linux::AIO::poll_fileno, |
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poll => 'r', async => 1, |
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cb => \&Linux::AIO::poll_cb ); |
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1.2 |
Linux::AIO::poll_wait |
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Wait till the result filehandle becomes ready for reading (simply |
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does a select on the filehandle. This is useful if you want to |
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synchronously wait for some requests to finish). |
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1.1 |
Linux::AIO::nreqs |
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Returns the number of requests currently outstanding. |
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aio_open $pathname, $flags, $mode, $callback |
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Asynchronously open or create a file and call the callback with the |
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filedescriptor (NOT a perl filehandle, sorry for that, but watch |
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out, this might change in the future). |
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aio_close $fh, $callback |
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Asynchronously close a file and call the callback with the result |
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code. |
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aio_read $fh,$offset,$length, $data,$dataoffset,$callback |
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aio_write $fh,$offset,$length, $data,$dataoffset,$callback |
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Reads or writes "length" bytes from the specified "fh" and "offset" |
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into the scalar given by "data" and offset "dataoffset" and calls |
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the callback without the actual number of bytes read (or "undef" on |
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error). |
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aio_stat $fh_or_path, $callback |
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aio_lstat $fh, $callback |
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Works like perl's "stat" or "lstat" in void context. The callback |
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will be called after the stat and the results will be available |
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using "stat _" or "-s _" etc... |
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Currently, the stats are always 64-bit-stats, i.e. instead of |
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returning an error when stat'ing a large file, the results will be |
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silently truncated unless perl itself is compiled with large file |
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support. |
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aio_unlink $pathname, $callback |
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Asynchronously unlink a file. |
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BUGS |
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This module has been extensively tested in a large and very busy |
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webserver for many years now. |
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- aio_open gives a fd, but all other functions expect a perl filehandle. |
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SEE ALSO |
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Coro. |
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AUTHOR |
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Marc Lehmann <schmorp@schmorp.de> |
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http://home.schmorp.de/ |
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