--- IO-AIO/AIO.pm 2005/07/10 17:07:44 1.1 +++ IO-AIO/AIO.pm 2005/07/10 21:04:24 1.5 @@ -9,35 +9,19 @@ =head1 DESCRIPTION This module implements asynchronous I/O using whatever means your -operating system supports. Currently, it falls back to Linux::AIO if that -module is available, or uses pthreads to emulato aio functionality. +operating system supports. -Currently, in this module a number of 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. +Currently, a number of 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. In the future, this module might make use of the native +aio functions available on many operating systems. However, they are often +not well-supported (Linux doesn't allow them on normal files currently, +for example), and they would only support aio_read and aio_write, so the +remaining functionality would have to be implemented using threads anyway. Although the module will work with in the presence of other threads, it is -not reentrant, so use appropriate locking yourself. - -=head2 API NOTES - -All the C calls are more or less thin wrappers around the syscall -with the same name (sans C). 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 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 +currently not reentrant, so use appropriate locking yourself. =cut @@ -45,84 +29,44 @@ use base 'Exporter'; +use Fcntl (); + BEGIN { - $VERSION = 0.1; + $VERSION = 0.2; @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); + @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs); require XSLoader; XSLoader::load IO::AIO, $VERSION; } -=item IO::AIO::min_parallel $nthreads +=head1 FUNCTIONS -Set the minimum number of AIO threads to C<$nthreads>. The default is -C<1>, which means a single asynchronous operation can be done at one time -(the number of outstanding operations, however, is unlimited). - -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 IO::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 at program end, to ensure -that all threads are killed and that there are no outstanding requests. +=head2 AIO FUNCTIONS -Under normal circumstances you don't need to call this function. - -=item $fileno = IO::AIO::poll_fileno - -Return the I. This filehandle must be -polled for reading by some mechanism outside this module (e.g. Event -or select, see below). If the pipe becomes readable you have to call -C to check the results. - -See C for an example. - -=item IO::AIO::poll_cb - -Process all outstanding events on the result pipe. You have to call this -regularly. Returns the number of events processed. Returns immediately -when no events are outstanding. - -You can use Event to multiplex, e.g.: - - Event->io (fd => IO::AIO::poll_fileno, - poll => 'r', async => 1, - cb => \&IO::AIO::poll_cb); - -=item IO::AIO::poll_wait - -Wait till the result filehandle becomes ready for reading (simply does a -select on the filehandle. This is useful if you want to synchronously wait -for some requests to finish). - -See C for an example. - -=item IO::AIO::nreqs +All the C calls are more or less thin wrappers around the syscall +with the same name (sans C). The arguments are similar or identical, +and they all accept an additional C<$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. -Returns the number of requests currently outstanding. +All functions that expect a filehandle will also accept a file descriptor. -Example: wait till there are no outstanding requests anymore: +The filenames you pass to these routines I 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. - IO::AIO::poll_wait, IO::AIO::poll_cb - while IO::AIO::nreqs; +=over 4 =item aio_open $pathname, $flags, $mode, $callback -Asynchronously open or create a file and call the callback with the -filedescriptor (NOT a perl filehandle, sorry for that, but watch out, this -might change in the future). +Asynchronously open or create a file and call the callback with a newly +created filehandle for the file. The pathname passed to C must be absolute. See API NOTES, above, for an explanation. @@ -133,10 +77,8 @@ Example: aio_open "/etc/passwd", O_RDONLY, 0, sub { - if ($_[0] >= 0) { - open my $fh, "<&$_[0]"; # create a copy for perl - aio_close $_[0], sub { }; # close the aio handle - print "open successful, fh is $fh\n"; + if ($_[0]) { + print "open successful, fh is $_[0]\n"; ... } else { die "open failed: $!\n"; @@ -145,7 +87,11 @@ =item aio_close $fh, $callback -Asynchronously close a file and call the callback with the result code. +Asynchronously close a file and call the callback with the result +code. I although accepted, you should not pass in a perl +filehandle here, as perl will likely close the file descriptor itself when +the filehandle is destroyed. Normally, you can safely call perls C +or just let filehandles go out of scope. =item aio_read $fh,$offset,$length, $data,$dataoffset,$callback @@ -216,8 +162,104 @@ Asynchronously call fdatasync on the given filehandle and call the callback with the fdatasync result code. +=back + +=head2 SUPPORT FUNCTIONS + +=over 4 + +=item $fileno = IO::AIO::poll_fileno + +Return the I. 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 to check the results. + +See C for an example. + +=item IO::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 => IO::AIO::poll_fileno, + poll => 'r', async => 1, + cb => \&IO::AIO::poll_cb); + +=item IO::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 for an example. + +=item IO::AIO::nreqs + +Returns the number of requests currently outstanding. + +Example: wait till there are no outstanding requests anymore: + + IO::AIO::poll_wait, IO::AIO::poll_cb + while IO::AIO::nreqs; + +=item IO::AIO::min_parallel $nthreads + +Set the minimum number of AIO threads to C<$nthreads>. The default is +C<1>, which means a single asynchronous operation can be done at one time +(the number of outstanding operations, however, is unlimited). + +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). With current Linux 2.6 versions, 4-32 +threads should be fine. + +Under normal circumstances you don't need to call this function, as this +module automatically starts some threads (the exact number might change, +and is currently 4). + +=item IO::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 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 $oldnreqs = IO::AIO::max_outstanding $nreqs + +Sets the maximum number of outstanding requests to C<$nreqs>. If you +try to queue up more than this number of requests, the caller will block until +some requests have been handled. + +The default is very large, so normally there is no practical limit. If you +queue up many requests in a loop it it often improves speed if you set +this to a relatively low number, such as C<100>. + +Under normal circumstances you don't need to call this function. + +=back + =cut +# support function to convert a fd into a perl filehandle +sub _fd2fh { + return undef if $_[0] < 0; + + # try to be perl5.6-compatible + local *AIO_FH; + open AIO_FH, "+<&=$_[0]" + or return undef; + + *AIO_FH +} + min_parallel 4; END { @@ -226,12 +268,6 @@ 1; -=back - -=head1 BUGS - - - aio_open gives a fd, but all other functions expect a perl filehandle. - =head1 SEE ALSO L, L.