[ViewVC] Diff of: cvs/Linux-AIO/AIO.pm

Comparing Linux-AIO/AIO.pm (file contents):
Revision 1.24 by root, Wed Jun 29 15:28:14 2005 UTC vs.
Revision 1.34 by root, Sun Jul 10 17:07:34 2005 UTC

  use Linux::AIO;
 =head1 DESCRIPTION
-This module implements asynchronous i/o using the means available to linux
+This module implements asynchronous I/O using the means available to Linux
-- clone. It does not hook into the POSIX aio_* functions because linux
+- clone. It does not hook into the POSIX aio_* functions because Linux
-does not yet support these in the kernel (and even if, it would only allow
+does not yet support these in the kernel (even as of 2.6.12, only O_DIRECT
-aio_read and write, not open and stat).
+files are supported) and even if, it would only allow aio_read and write,
+not open, stat and so on.
 Instead, in this module a number of (non-posix) threads are started that
 execute your read/writes and signal their completion. You don't need
 thread support in your libc or perl, and the threads created by this
 module will not be visible to the pthreads library.
 NOTICE: the threads created by this module will automatically be killed
 when the thread calling min_parallel exits. Make sure you only ever call
 min_parallel from the same thread that loaded this module.
-Although the module will work with threads, it is not reentrant, so use
+Although the module will work with in the presence of other threads, it is
-appropriate locking yourself.
+not reentrant, so use appropriate locking yourself.
+=head2 API NOTES
+All the C<aio_*> calls are more or less thin wrappers around the syscall
+with the same name (sans C<aio_>). The arguments are similar or identical,
+and they all accept an additional C<$callback> argument which must be
+a code reference. This code reference will get called with the syscall
+return code (e.g. most syscalls return C<-1> on error, unlike perl, which
+usually delivers "false") as it's sole argument when the given syscall has
+been executed asynchronously.
+All functions that expect a filehandle will also accept a file descriptor.
+The filenames you pass to these routines I<must> be absolute. The reason
+is that at the time the request is being executed, the current working
+directory could have changed. Alternatively, you can make sure that you
+never change the current working directory.
 =over 4
 =cut
 package Linux::AIO;
 use base 'Exporter';
 BEGIN {
-   $VERSION = 1.5;
+   $VERSION = 1.71;
-   @EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink);
+   @EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink
+                aio_fsync aio_fdatasync aio_readahead);
    @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel nreqs);
    require XSLoader;
    XSLoader::load Linux::AIO, $VERSION;
 }
 It is recommended to keep the number of threads low, as some linux
 kernel versions will scale negatively with the number of threads (higher
 parallelity => MUCH higher latency).
+Under normal circumstances you don't need to call this function, as this
+module automatically starts a single async thread.
 =item Linux::AIO::max_parallel $nthreads
 Sets the maximum number of AIO threads to C<$nthreads>. If more than
 the specified number of threads are currently running, kill them. This
 function blocks until the limit is reached.
 This module automatically runs C<max_parallel 0> at program end, to ensure
 that all threads are killed and that there are no outstanding requests.
+Under normal circumstances you don't need to call this function.
 =item $fileno = Linux::AIO::poll_fileno
 Return the I<request result pipe filehandle>. This filehandle must be
 polled for reading by some mechanism outside this module (e.g. Event
 or select, see below). If the pipe becomes readable you have to call
 C<poll_cb> to check the results.
+See C<poll_cb> for an example.
 =item Linux::AIO::poll_cb
 Process all outstanding events on the result pipe. You have to call this
 regularly. Returns the number of events processed. Returns immediately
 when no events are outstanding.
 You can use Event to multiplex, e.g.:
    Event->io (fd => Linux::AIO::poll_fileno,
               poll => 'r', async => 1,
-              cb => \&Linux::AIO::poll_cb );
+              cb => \&Linux::AIO::poll_cb);
 =item Linux::AIO::poll_wait
 Wait till the result filehandle becomes ready for reading (simply does a
 select on the filehandle. This is useful if you want to synchronously wait
 for some requests to finish).
+See C<nreqs> for an example.
 =item Linux::AIO::nreqs
 Returns the number of requests currently outstanding.
+Example: wait till there are no outstanding requests anymore:
+   Linux::AIO::poll_wait, Linux::AIO::poll_cb
+      while Linux::AIO::nreqs;
-=item aio_open  $pathname, $flags, $mode, $callback
+=item aio_open $pathname, $flags, $mode, $callback
 Asynchronously open or create a file and call the callback with the
 filedescriptor (NOT a perl filehandle, sorry for that, but watch out, this
 might change in the future).
+The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
+for an explanation.
+The C<$mode> argument is a bitmask. See the C<Fcntl> module for a
+list. They are the same as used in C<sysopen>.
+Example:
+   aio_open "/etc/passwd", O_RDONLY, 0, sub {
+      if ($_[0] >= 0) {
+         open my $fh, "<&$_[0]";   # create a copy for perl
+         aio_close $_[0], sub { }; # close the aio handle
+         print "open successful, fh is $fh\n";
+         ...
+      } else {
+         die "open failed: $!\n";
+      }
+   };
 =item aio_close $fh, $callback
 Asynchronously close a file and call the callback with the result code.
 =item aio_read  $fh,$offset,$length, $data,$dataoffset,$callback
 =item aio_write $fh,$offset,$length, $data,$dataoffset,$callback
 Reads or writes C<length> bytes from the specified C<fh> and C<offset>
 into the scalar given by C<data> and offset C<dataoffset> and calls the
-callback without the actual number of bytes read (or C<undef> on error).
+callback without the actual number of bytes read (or -1 on error, just
+like the syscall).
+Example: Read 15 bytes at offset 7 into scalar C<$buffer>, strating at
+offset C<0> within the scalar:
+   aio_read $fh, 7, 15, $buffer, 0, sub {
+      $_[0] >= 0 or die "read error: $!";
+      print "read <$buffer>\n";
+   };
+=item aio_readahead $fh,$offset,$length, $callback
+Asynchronously reads the specified byte range into the page cache, using
+the C<readahead> syscall.
+readahead() populates the page cache with data from a file so that
+subsequent reads from that file will not block on disk I/O. The C<$offset>
+argument specifies the starting point from which data is to be read and
+C<$length> specifies the number of bytes to be read. I/O is performed in
+whole pages, so that offset is effectively rounded down to a page boundary
+and bytes are read up to the next page boundary greater than or equal to
+(off-set+length). aio_readahead() does not read beyond the end of the
+file. The current file offset of the file is left unchanged.
 =item aio_stat  $fh_or_path, $callback
 =item aio_lstat $fh, $callback
 Works like perl's C<stat> or C<lstat> in void context. The callback will
 be called after the stat and the results will be available using C<stat _>
 or C<-s _> etc...
+The pathname passed to C<aio_stat> must be absolute. See API NOTES, above,
+for an explanation.
 Currently, the stats are always 64-bit-stats, i.e. instead of returning an
 error when stat'ing a large file, the results will be silently truncated
 unless perl itself is compiled with large file support.
+Example: Print the length of F</etc/passwd>:
+   aio_stat "/etc/passwd", sub {
+      $_[0] and die "stat failed: $!";
+      print "size is ", -s _, "\n";
+   };
-=item aio_unlink  $pathname, $callback
+=item aio_unlink $pathname, $callback
-Asynchronously unlink a file.
+Asynchronously unlink (delete) a file and call the callback with the
+result code.
+=item aio_fsync $fh, $callback
+Asynchronously call fsync on the given filehandle and call the callback
+with the fsync result code.
+=item aio_fdatasync $fh, $callback
+Asynchronously call fdatasync on the given filehandle and call the
+callback with the fdatasync result code.
 =cut
 min_parallel 1;
    - aio_open gives a fd, but all other functions expect a perl filehandle.
 =head1 SEE ALSO
-L<Coro>.
+L<Coro>, L<IO::AIO>.
 =head1 AUTHOR
  Marc Lehmann <schmorp@schmorp.de>
  http://home.schmorp.de/

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Comparing Linux-AIO/AIO.pm (file contents): Revision 1.24 by root, Wed Jun 29 15:28:14 2005 UTC vs. Revision 1.34 by root, Sun Jul 10 17:07:34 2005 UTC

Diff Legend

Comparing Linux-AIO/AIO.pm (file contents):
Revision 1.24 by root, Wed Jun 29 15:28:14 2005 UTC vs.
Revision 1.34 by root, Sun Jul 10 17:07:34 2005 UTC