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… …
4SYNOPSIS 4SYNOPSIS
5 use IO::AIO; 5 use IO::AIO;
6 6
7DESCRIPTION 7DESCRIPTION
8 This module implements asynchronous I/O using whatever means your 8 This module implements asynchronous I/O using whatever means your
9 operating system supports. Currently, it falls back to Linux::AIO if 9 operating system supports.
10 that module is available, or uses pthreads to emulato aio functionality.
11 10
12 Currently, in this module a number of threads are started that execute 11 Currently, a number of threads are started that execute your read/writes
13 your read/writes and signal their completion. You don't need thread 12 and signal their completion. You don't need thread support in your libc
14 support in your libc or perl, and the threads created by this module 13 or perl, and the threads created by this module will not be visible to
15 will not be visible to the pthreads library. 14 the pthreads library. In the future, this module might make use of the
15 native aio functions available on many operating systems. However, they
16 are often not well-supported (Linux doesn't allow them on normal files
17 currently, for example), and they would only support aio_read and
18 aio_write, so the remaining functionality would have to be implemented
19 using threads anyway.
16 20
17 Although the module will work with in the presence of other threads, it 21 Although the module will work with in the presence of other threads, it
18 is not reentrant, so use appropriate locking yourself. 22 is currently not reentrant, so use appropriate locking yourself.
19 23
20 API NOTES 24 API NOTES
21 All the "aio_*" calls are more or less thin wrappers around the syscall 25 All the "aio_*" calls are more or less thin wrappers around the syscall
22 with the same name (sans "aio_"). The arguments are similar or 26 with the same name (sans "aio_"). The arguments are similar or
23 identical, and they all accept an additional $callback argument which 27 identical, and they all accept an additional $callback argument which
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90 94
91 IO::AIO::poll_wait, IO::AIO::poll_cb 95 IO::AIO::poll_wait, IO::AIO::poll_cb
92 while IO::AIO::nreqs; 96 while IO::AIO::nreqs;
93 97
94 aio_open $pathname, $flags, $mode, $callback 98 aio_open $pathname, $flags, $mode, $callback
95 Asynchronously open or create a file and call the callback with the 99 Asynchronously open or create a file and call the callback with a
96 filedescriptor (NOT a perl filehandle, sorry for that, but watch 100 newly created filehandle for the file.
97 out, this might change in the future). 101
102 The pathname passed to "aio_open" must be absolute. See API NOTES,
103 above, for an explanation.
98 104
99 The $mode argument is a bitmask. See the "Fcntl" module for a list. 105 The $mode argument is a bitmask. See the "Fcntl" module for a list.
100 They are the same as used in "sysopen". 106 They are the same as used in "sysopen".
101 107
102 Example: 108 Example:
103 109
104 aio_open "/etc/passwd", O_RDONLY, 0, sub { 110 aio_open "/etc/passwd", O_RDONLY, 0, sub {
105 if ($_[0] >= 0) { 111 if ($_[0]) {
106 open my $fh, "<&$_[0]"; # create a copy for perl
107 aio_close $_[0], sub { }; # close the aio handle
108 print "open successful, fh is $fh\n"; 112 print "open successful, fh is $_[0]\n";
109 ... 113 ...
110 } else { 114 } else {
111 die "open failed: $!\n"; 115 die "open failed: $!\n";
112 } 116 }
113 }; 117 };
114 118
115 aio_close $fh, $callback 119 aio_close $fh, $callback
116 Asynchronously close a file and call the callback with the result 120 Asynchronously close a file and call the callback with the result
117 code. 121 code. *WARNING:* although accepted, you should not pass in a perl
122 filehandle here, as perl will likely close the file descriptor
123 itself when the filehandle is destroyed. Normally, you can safely
124 call perls "close" or just let filehandles go out of scope.
118 125
119 aio_read $fh,$offset,$length, $data,$dataoffset,$callback 126 aio_read $fh,$offset,$length, $data,$dataoffset,$callback
120 aio_write $fh,$offset,$length, $data,$dataoffset,$callback 127 aio_write $fh,$offset,$length, $data,$dataoffset,$callback
121 Reads or writes "length" bytes from the specified "fh" and "offset" 128 Reads or writes "length" bytes from the specified "fh" and "offset"
122 into the scalar given by "data" and offset "dataoffset" and calls 129 into the scalar given by "data" and offset "dataoffset" and calls
… …
131 print "read <$buffer>\n"; 138 print "read <$buffer>\n";
132 }; 139 };
133 140
134 aio_readahead $fh,$offset,$length, $callback 141 aio_readahead $fh,$offset,$length, $callback
135 Asynchronously reads the specified byte range into the page cache, 142 Asynchronously reads the specified byte range into the page cache,
136 using the "readahead" syscall. 143 using the "readahead" syscall. If that syscall doesn't exist the
144 status will be -1 and $! is set to ENOSYS.
137 145
138 readahead() populates the page cache with data from a file so that 146 readahead() populates the page cache with data from a file so that
139 subsequent reads from that file will not block on disk I/O. The 147 subsequent reads from that file will not block on disk I/O. The
140 $offset argument specifies the starting point from which data is to 148 $offset argument specifies the starting point from which data is to
141 be read and $length specifies the number of bytes to be read. I/O is 149 be read and $length specifies the number of bytes to be read. I/O is
… …
177 aio_fdatasync $fh, $callback 185 aio_fdatasync $fh, $callback
178 Asynchronously call fdatasync on the given filehandle and call the 186 Asynchronously call fdatasync on the given filehandle and call the
179 callback with the fdatasync result code. 187 callback with the fdatasync result code.
180 188
181BUGS 189BUGS
182 This module has been extensively tested in a large and very busy 190 - could be optimized to use more semaphores instead of filehandles.
183 webserver for many years now.
184
185 - aio_open gives a fd, but all other functions expect a perl filehandle.
186 191
187SEE ALSO 192SEE ALSO
188 Coro. 193 Coro, Linux::AIO.
189 194
190AUTHOR 195AUTHOR
191 Marc Lehmann <schmorp@schmorp.de> 196 Marc Lehmann <schmorp@schmorp.de>
192 http://home.schmorp.de/ 197 http://home.schmorp.de/
193 198

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