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Revision: 1.1
Committed: Tue Mar 8 20:19:00 2005 UTC (19 years, 8 months ago) by root
Branch: MAIN
CVS Tags: rel-1_6
Log Message:
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File Contents

# User Rev Content
1 root 1.1 NAME
2     Linux::AIO - linux-specific aio implemented using clone
3    
4     SYNOPSIS
5     use Linux::AIO;
6    
7     DESCRIPTION
8     This module implements asynchronous i/o using the means available to
9     linux - clone. It does not hook into the POSIX aio_* functions because
10     linux does not yet support these in the kernel (and even if, it would
11     only allow aio_read and write, not open and stat).
12    
13     Instead, in this module a number of (non-posix) threads are started that
14     execute your read/writes and signal their completion. You don't need
15     thread support in your libc or perl, and the threads created by this
16     module will not be visible to the pthreads library.
17    
18     NOTICE: the threads created by this module will automatically be killed
19     when the thread calling min_parallel exits. Make sure you only ever call
20     min_parallel from the same thread that loaded this module.
21    
22     Although the module will work with threads, it is not reentrant, so use
23     appropriate locking yourself.
24    
25     Linux::AIO::min_parallel $nthreads
26     Set the minimum number of AIO threads to $nthreads. The default is
27     1, which means a single asynchronous operation can be done at one
28     time (the number of outstanding operations, however, is unlimited).
29    
30     It is recommended to keep the number of threads low, as many linux
31     kernel versions will scale negatively with the number of threads
32     (higher parallelity => MUCH higher latency).
33    
34     $fileno = Linux::AIO::poll_fileno
35     Return the *request result pipe filehandle*. This filehandle must be
36     polled for reading by some mechanism outside this module (e.g. Event
37     or select, see below). If the pipe becomes readable you have to call
38     "poll_cb" to check the results.
39    
40     Linux::AIO::poll_cb
41     Process all outstanding events on the result pipe. You have to call
42     this regularly. Returns the number of events processed. Returns
43     immediately when no events are outstanding.
44    
45     You can use Event to multiplex, e.g.:
46    
47     Event->io (fd => Linux::AIO::poll_fileno,
48     poll => 'r', async => 1,
49     cb => \&Linux::AIO::poll_cb );
50    
51     Linux::AIO::nreqs
52     Returns the number of requests currently outstanding.
53    
54     aio_open $pathname, $flags, $mode, $callback
55     Asynchronously open or create a file and call the callback with the
56     filedescriptor (NOT a perl filehandle, sorry for that, but watch
57     out, this might change in the future).
58    
59     aio_close $fh, $callback
60     Asynchronously close a file and call the callback with the result
61     code.
62    
63     aio_read $fh,$offset,$length, $data,$dataoffset,$callback
64     aio_write $fh,$offset,$length, $data,$dataoffset,$callback
65     Reads or writes "length" bytes from the specified "fh" and "offset"
66     into the scalar given by "data" and offset "dataoffset" and calls
67     the callback without the actual number of bytes read (or "undef" on
68     error).
69    
70     aio_stat $fh_or_path, $callback
71     aio_lstat $fh, $callback
72     Works like perl's "stat" or "lstat" in void context. The callback
73     will be called after the stat and the results will be available
74     using "stat _" or "-s _" etc...
75    
76     Currently, the stats are always 64-bit-stats, i.e. instead of
77     returning an error when stat'ing a large file, the results will be
78     silently truncated unless perl itself is compiled with large file
79     support.
80    
81     aio_unlink $pathname, $callback
82     Asynchronously unlink a file.
83    
84     BUGS
85     This module has been extensively tested in a large and very busy
86     webserver for many years now.
87    
88     - aio_open gives a fd, but all other functions expect a perl filehandle.
89    
90     SEE ALSO
91     Coro.
92    
93     AUTHOR
94     Marc Lehmann <schmorp@schmorp.de>
95     http://home.schmorp.de/
96