--- IO-AIO/AIO.pm 2006/10/24 11:57:30 1.71 +++ IO-AIO/AIO.pm 2006/10/28 23:32:29 1.86 @@ -53,19 +53,130 @@ This module implements asynchronous I/O using whatever means your operating system supports. -Currently, a number of threads are started that execute your read/writes -and signal their completion. You don't need thread support in perl, and -the threads created by this module will not be visible to perl. 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 currently not reentrant in any way, so use appropriate locking -yourself, always call C from within the same thread, or never -call C (or other C functions) recursively. +Asynchronous means that operations that can normally block your program +(e.g. reading from disk) will be done asynchronously: the operation +will still block, but you can do something else in the meantime. This +is extremely useful for programs that need to stay interactive even +when doing heavy I/O (GUI programs, high performance network servers +etc.), but can also be used to easily do operations in parallel that are +normally done sequentially, e.g. stat'ing many files, which is much faster +on a RAID volume or over NFS when you do a number of stat operations +concurrently. + +While this works on all types of file descriptors (for example sockets), +using these functions on file descriptors that support nonblocking +operation (again, sockets, pipes etc.) is very inefficient. Use an event +loop for that (such as the L module): IO::AIO will naturally +fit into such an event loop itself. + +In this version, a number of threads are started that execute your +requests and signal their completion. You don't need thread support +in perl, and the threads created by this module will not be visible +to perl. 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 or restricted (GNU/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 (Perl-) +threads, it is currently not reentrant in any way, so use appropriate +locking yourself, always call C from within the same thread, or +never call C (or other C functions) recursively. + +=head2 EXAMPLE + +This is a simple example that uses the Event module and loads +F asynchronously: + + use Fcntl; + use Event; + use IO::AIO; + + # register the IO::AIO callback with Event + Event->io (fd => IO::AIO::poll_fileno, + poll => 'r', + cb => \&IO::AIO::poll_cb); + + # queue the request to open /etc/passwd + aio_open "/etc/passwd", O_RDONLY, 0, sub { + my $fh = $_[0] + or die "error while opening: $!"; + + # stat'ing filehandles is generally non-blocking + my $size = -s $fh; + + # queue a request to read the file + my $contents; + aio_read $fh, 0, $size, $contents, 0, sub { + $_[0] == $size + or die "short read: $!"; + + close $fh; + + # file contents now in $contents + print $contents; + + # exit event loop and program + Event::unloop; + }; + }; + + # possibly queue up other requests, or open GUI windows, + # check for sockets etc. etc. + + # process events as long as there are some: + Event::loop; + +=head1 REQUEST ANATOMY AND LIFETIME + +Every C function creates a request. which is a C data structure not +directly visible to Perl. + +If called in non-void context, every request function returns a Perl +object representing the request. In void context, nothing is returned, +which saves a bit of memory. + +The perl object is a fairly standard ref-to-hash object. The hash contents +are not used by IO::AIO so you are free to store anything you like in it. + +During their existance, aio requests travel through the following states, +in order: + +=over 4 + +=item ready + +Immediately after a request is created it is put into the ready state, +waiting for a thread to execute it. + +=item execute + +A thread has accepted the request for processing and is currently +executing it (e.g. blocking in read). + +=item pending + +The request has been executed and is waiting for result processing. + +While request submission and execution is fully asynchronous, result +processing is not and relies on the perl interpreter calling C +(or another function with the same effect). + +=item result + +The request results are processed synchronously by C. + +The C function will process all outstanding aio requests by +calling their callbacks, freeing memory associated with them and managing +any groups they are contained in. + +=item done + +Request has reached the end of its lifetime and holds no resources anymore +(except possibly for the Perl object, but its connection to the actual +aio request is severed and calling its methods will either do nothing or +result in a runtime error). =cut @@ -77,15 +188,17 @@ use base 'Exporter'; BEGIN { - our $VERSION = '2.0'; + our $VERSION = '2.1'; our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move - aio_group aio_nop); + aio_copy aio_group aio_nop aio_mknod); our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice)); our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush - min_parallel max_parallel max_outstanding nreqs); + min_parallel max_parallel max_idle + nreqs nready npending nthreads + max_poll_time max_poll_reqs); @IO::AIO::GRP::ISA = 'IO::AIO::REQ'; @@ -126,13 +239,16 @@ =over 4 -=item aioreq_pri $pri +=item $prev_pri = aioreq_pri [$pri] + +Returns the priority value that would be used for the next request and, if +C<$pri> is given, sets the priority for the next aio request. -Sets the priority for the next aio request. The default priority -is C<0>, the minimum and maximum priorities are C<-4> and C<4>, -respectively. Requests with higher priority will be serviced first. +The default priority is C<0>, the minimum and maximum priorities are C<-4> +and C<4>, respectively. Requests with higher priority will be serviced +first. -The priority will be reset to C<0> after each call to one of the C +The priority will be reset to C<0> after each call to one of the C functions. Example: open a file with low priority, then read something from it with @@ -213,74 +329,6 @@ print "read $_[0] bytes: <$buffer>\n"; }; -=item aio_move $srcpath, $dstpath, $callback->($status) - -Try to move the I (directories not supported as either source or -destination) from C<$srcpath> to C<$dstpath> and call the callback with -the C<0> (error) or C<-1> ok. - -This is a composite request that tries to rename(2) the file first. If -rename files with C, it creates the destination file with mode 0200 -and copies the contents of the source file into it using C, -followed by restoring atime, mtime, access mode and uid/gid, in that -order, and unlinking the C<$srcpath>. - -If an error occurs, the partial destination file will be unlinked, if -possible, except when setting atime, mtime, access mode and uid/gid, where -errors are being ignored. - -=cut - -sub aio_move($$$) { - my ($src, $dst, $cb) = @_; - - my $grp = aio_group $cb; - - add $grp aio_rename $src, $dst, sub { - if ($_[0] && $! == EXDEV) { - add $grp aio_open $src, O_RDONLY, 0, sub { - if (my $src_fh = $_[0]) { - my @stat = stat $src_fh; - - add $grp aio_open $dst, O_WRONLY, 0200, sub { - if (my $dst_fh = $_[0]) { - add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub { - close $src_fh; - - if ($_[0] == $stat[7]) { - utime $stat[8], $stat[9], $dst; - chmod $stat[2] & 07777, $dst_fh; - chown $stat[4], $stat[5], $dst_fh; - close $dst_fh; - - add $grp aio_unlink $src, sub { - $grp->result ($_[0]); - }; - } else { - my $errno = $!; - add $grp aio_unlink $dst, sub { - $! = $errno; - $grp->result (-1); - }; - } - }; - } else { - $grp->result (-1); - } - }, - - } else { - $grp->result (-1); - } - }; - } else { - $grp->result ($_[0]); - } - }; - - $grp -} - =item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts @@ -345,6 +393,16 @@ Asynchronously unlink (delete) a file and call the callback with the result code. +=item aio_mknod $path, $mode, $dev, $callback->($status) + +[EXPERIMENTAL] + +Asynchronously create a device node (or fifo). See mknod(2). + +The only (POSIX-) portable way of calling this function is: + + aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... + =item aio_link $srcpath, $dstpath, $callback->($status) Asynchronously create a new link to the existing object at C<$srcpath> at @@ -374,17 +432,119 @@ The callback a single argument which is either C or an array-ref with the filenames. +=item aio_copy $srcpath, $dstpath, $callback->($status) + +Try to copy the I (directories not supported as either source or +destination) from C<$srcpath> to C<$dstpath> and call the callback with +the C<0> (error) or C<-1> ok. + +This is a composite request that it creates the destination file with +mode 0200 and copies the contents of the source file into it using +C, followed by restoring atime, mtime, access mode and +uid/gid, in that order. + +If an error occurs, the partial destination file will be unlinked, if +possible, except when setting atime, mtime, access mode and uid/gid, where +errors are being ignored. + +=cut + +sub aio_copy($$;$) { + my ($src, $dst, $cb) = @_; + + my $pri = aioreq_pri; + my $grp = aio_group $cb; + + aioreq_pri $pri; + add $grp aio_open $src, O_RDONLY, 0, sub { + if (my $src_fh = $_[0]) { + my @stat = stat $src_fh; + + aioreq_pri $pri; + add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub { + if (my $dst_fh = $_[0]) { + aioreq_pri $pri; + add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub { + if ($_[0] == $stat[7]) { + $grp->result (0); + close $src_fh; + + # those should not normally block. should. should. + utime $stat[8], $stat[9], $dst; + chmod $stat[2] & 07777, $dst_fh; + chown $stat[4], $stat[5], $dst_fh; + close $dst_fh; + } else { + $grp->result (-1); + close $src_fh; + close $dst_fh; + + aioreq $pri; + add $grp aio_unlink $dst; + } + }; + } else { + $grp->result (-1); + } + }, + + } else { + $grp->result (-1); + } + }; + + $grp +} + +=item aio_move $srcpath, $dstpath, $callback->($status) + +Try to move the I (directories not supported as either source or +destination) from C<$srcpath> to C<$dstpath> and call the callback with +the C<0> (error) or C<-1> ok. + +This is a composite request that tries to rename(2) the file first. If +rename files with C, it copies the file with C and, if +that is successful, unlinking the C<$srcpath>. + +=cut + +sub aio_move($$;$) { + my ($src, $dst, $cb) = @_; + + my $pri = aioreq_pri; + my $grp = aio_group $cb; + + aioreq_pri $pri; + add $grp aio_rename $src, $dst, sub { + if ($_[0] && $! == EXDEV) { + aioreq_pri $pri; + add $grp aio_copy $src, $dst, sub { + $grp->result ($_[0]); + + if (!$_[0]) { + aioreq_pri $pri; + add $grp aio_unlink $src; + } + }; + } else { + $grp->result ($_[0]); + } + }; + + $grp +} + =item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) Scans a directory (similar to C) but additionally tries to -separate the entries of directory C<$path> into two sets of names, ones -you can recurse into (directories or links to them), and ones you cannot -recurse into (everything else). +efficiently separate the entries of directory C<$path> into two sets of +names, directories you can recurse into (directories), and ones you cannot +recurse into (everything else, including symlinks to directories). C is a composite request that creates of many sub requests_ C<$maxreq> specifies the maximum number of outstanding aio requests that this function generates. If it is C<< <= 0 >>, then a suitable default -will be chosen (currently 6). +will be chosen (currently 4). On error, the callback is called without arguments, otherwise it receives two array-refs with path-relative entry names. @@ -431,22 +591,27 @@ sub aio_scandir($$$) { my ($path, $maxreq, $cb) = @_; + my $pri = aioreq_pri; + my $grp = aio_group $cb; - $maxreq = 6 if $maxreq <= 0; + $maxreq = 4 if $maxreq <= 0; # stat once + aioreq_pri $pri; add $grp aio_stat $path, sub { return $grp->result () if $_[0]; my $now = time; my $hash1 = join ":", (stat _)[0,1,3,7,9]; # read the directory entries + aioreq_pri $pri; add $grp aio_readdir $path, sub { my $entries = shift or return $grp->result (); # stat the dir another time + aioreq_pri $pri; add $grp aio_stat $path, sub { my $hash2 = join ":", (stat _)[0,1,3,7,9]; @@ -471,55 +636,37 @@ my (@dirs, @nondirs); - my ($statcb, $schedcb); - my $nreq = 0; - - my $statgrp = add $grp aio_group; - - $schedcb = sub { - if (@$entries) { - if ($nreq < $maxreq) { - my $ent = pop @$entries; - $nreq++; - add $statgrp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) }; - } - } elsif (!$nreq) { - # finished - $statgrp->cancel; - undef $statcb; - undef $schedcb; - $grp->result (\@dirs, \@nondirs); - } + my $statgrp = add $grp aio_group sub { + $grp->result (\@dirs, \@nondirs); }; - $statcb = sub { - my ($status, $entry) = @_; - if ($status < 0) { - $nreq--; - push @nondirs, $entry; - &$schedcb; - } else { - # need to check for real directory - add $grp aio_lstat "$path/$entry", sub { - $nreq--; - - if (-d _) { - push @dirs, $entry; - - if (!--$ndirs) { - push @nondirs, @$entries; - $entries = []; + limit $statgrp $maxreq; + feed $statgrp sub { + return unless @$entries; + my $entry = pop @$entries; + + aioreq_pri $pri; + add $statgrp aio_stat "$path/$entry/.", sub { + if ($_[0] < 0) { + push @nondirs, $entry; + } else { + # need to check for real directory + aioreq_pri $pri; + add $statgrp aio_lstat "$path/$entry", sub { + if (-d _) { + push @dirs, $entry; + + unless (--$ndirs) { + push @nondirs, @$entries; + feed $statgrp; + } + } else { + push @nondirs, $entry; } - } else { - push @nondirs, $entry; } - - &$schedcb; } - } + }; }; - - &$schedcb while @$entries && $nreq < $maxreq; }; }; }; @@ -542,8 +689,6 @@ =item aio_group $callback->(...) -[EXPERIMENTAL] - This is a very special aio request: Instead of doing something, it is a container for other aio requests, which is useful if you want to bundle many requests into a single, composite, request with a definite callback @@ -593,14 +738,6 @@ All non-aggregate C functions return an object of this class when called in non-void context. -A request always moves through the following five states in its lifetime, -in order: B (request has been created, but has not been executed -yet), B (request is currently being executed), B -(request has been executed but callback has not been called yet), -B (results are being processed synchronously, includes calling the -callback) and B (request has reached the end of its lifetime and -holds no resources anymore). - =over 4 =item cancel $req @@ -663,10 +800,6 @@ =item * You must not add requests to a group from within the group callback (or any later time). -=item * This does not harmonise well with C, so best do -not combine C with it. Groups and feeders are recommended for -this kind of concurrency-limiting. - =back Their lifetime, simplified, looks like this: when they are empty, they @@ -691,14 +824,31 @@ Returns all its arguments. +=item $grp->cancel_subs + +Cancel all subrequests and clears any feeder, but not the group request +itself. Useful when you queued a lot of events but got a result early. + =item $grp->result (...) Set the result value(s) that will be passed to the group callback when all -subrequests have finished. By default, no argument will be passed. +subrequests have finished and set thre groups errno to the current value +of errno (just like calling C without an error number). By default, +no argument will be passed and errno is zero. -=item feed $grp $callback->($grp) +=item $grp->errno ([$errno]) + +Sets the group errno value to C<$errno>, or the current value of errno +when the argument is missing. -[VERY EXPERIMENTAL] +Every aio request has an associated errno value that is restored when +the callback is invoked. This method lets you change this value from its +default (0). + +Calling C will also set errno, so make sure you either set C<$!> +before the call to C, or call c after it. + +=item feed $grp $callback->($grp) Sets a feeder/generator on this group: every group can have an attached generator that generates requests if idle. The idea behind this is that, @@ -745,6 +895,8 @@ =head2 SUPPORT FUNCTIONS +=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION + =over 4 =item $fileno = IO::AIO::poll_fileno @@ -758,9 +910,13 @@ =item IO::AIO::poll_cb -Process all outstanding events on the result pipe. You have to call this +Process some 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. +when no events are outstanding. The amount of events processed depends on +the settings of C and C. + +If not all requests were processed for whatever reason, the filehandle +will still be ready when C returns. Example: Install an Event watcher that automatically calls IO::AIO::poll_cb with high priority: @@ -769,23 +925,50 @@ poll => 'r', async => 1, cb => \&IO::AIO::poll_cb); +=item IO::AIO::max_poll_reqs $nreqs + +=item IO::AIO::max_poll_time $seconds + +These set the maximum number of requests (default C<0>, meaning infinity) +that are being processed by C in one call, respectively +the maximum amount of time (default C<0>, meaning infinity) spent in +C to process requests (more correctly the mininum amount +of time C is allowed to use). + +Setting these is useful if you want to ensure some level of +interactiveness when perl is not fast enough to process all requests in +time. + +For interactive programs, values such as C<0.01> to C<0.1> should be fine. + +Example: Install an Event watcher that automatically calls +IO::AIO::poll_some with low priority, to ensure that other parts of the +program get the CPU sometimes even under high AIO load. + + # try not to spend much more than 0.1s in poll_cb + IO::AIO::max_poll_time 0.1; + + # use a low priority so other tasks have priority + Event->io (fd => IO::AIO::poll_fileno, + poll => 'r', nice => 1, + cb => &IO::AIO::poll_cb); + =item IO::AIO::poll_wait Wait till the result filehandle becomes ready for reading (simply does a -C 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 +=item IO::AIO::poll -Returns the number of requests currently outstanding (i.e. for which their -callback has not been invoked yet). +Waits until some requests have been handled. -Example: wait till there are no outstanding requests anymore: +Strictly equivalent to: IO::AIO::poll_wait, IO::AIO::poll_cb - while IO::AIO::nreqs; + if IO::AIO::nreqs; =item IO::AIO::flush @@ -796,14 +979,7 @@ IO::AIO::poll_wait, IO::AIO::poll_cb while IO::AIO::nreqs; -=item IO::AIO::poll - -Waits until some requests have been handled. - -Strictly equivalent to: - - IO::AIO::poll_wait, IO::AIO::poll_cb - if IO::AIO::nreqs; +=head3 CONTROLLING THE NUMBER OF THREADS =item IO::AIO::min_parallel $nthreads @@ -813,7 +989,9 @@ however, is unlimited). IO::AIO starts threads only on demand, when an AIO request is queued and -no free thread exists. +no free thread exists. Please note that queueing up a hundred requests can +create demand for a hundred threads, even if it turns out that everything +is in the cache and could have been processed faster by a single thread. It is recommended to keep the number of threads relatively low, as some Linux kernel versions will scale negatively with the number of threads @@ -837,23 +1015,60 @@ Under normal circumstances you don't need to call this function. -=item $oldnreqs = IO::AIO::max_outstanding $nreqs +=item IO::AIO::max_idle $nthreads -[DEPRECATED] +Limit the number of threads (default: 4) that are allowed to idle (i.e., +threads that did not get a request to process within 10 seconds). That +means if a thread becomes idle while C<$nthreads> other threads are also +idle, it will free its resources and exit. + +This is useful when you allow a large number of threads (e.g. 100 or 1000) +to allow for extremely high load situations, but want to free resources +under normal circumstances (1000 threads can easily consume 30MB of RAM). + +The default is probably ok in most situations, especially if thread +creation is fast. If thread creation is very slow on your system you might +want to use larger values. + +=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs + +This is a very bad function to use in interactive programs because it +blocks, and a bad way to reduce concurrency because it is inexact: Better +use an C together with a feed callback. Sets the maximum number of outstanding requests to C<$nreqs>. If you -try to queue up more than this number of requests, the caller will block until -some requests have been handled. +to queue up more than this number of requests, the next call to the +C (and C and other functions calling C) +function will block until the limit is no longer exceeded. + +The default value is very large, so there is no practical limit on the +number of outstanding requests. + +You can still queue as many requests as you want. Therefore, +C is mainly useful in simple scripts (with low values) or +as a stop gap to shield against fatal memory overflow (with large values). -The default is very large, so normally there is no practical limit. If you -queue up many requests in a loop it often improves speed if you set -this to a relatively low number, such as C<100>. - -This function does not work well together with C's, and their -feeder interface is better suited to limiting concurrency, so do not use -this function. +=head3 STATISTICAL INFORMATION -Under normal circumstances you don't need to call this function. +=item IO::AIO::nreqs + +Returns the number of requests currently in the ready, execute or pending +states (i.e. for which their callback has not been invoked yet). + +Example: wait till there are no outstanding requests anymore: + + IO::AIO::poll_wait, IO::AIO::poll_cb + while IO::AIO::nreqs; + +=item IO::AIO::nready + +Returns the number of requests currently in the ready state (not yet +executed). + +=item IO::AIO::npending + +Returns the number of requests currently in the pending state (executed, +but not yet processed by poll_cb). =back @@ -878,8 +1093,9 @@ min_parallel 8; END { - max_parallel 0; -} + min_parallel 1; + flush; +}; 1; @@ -890,9 +1106,9 @@ Before the fork, IO::AIO enters a quiescent state where no requests can be added in other threads and no results will be processed. After the fork the parent simply leaves the quiescent state and continues -request/result processing, while the child clears the request/result -queue (so the requests started before the fork will only be handled in -the parent). Threads will be started on demand until the limit ste in the +request/result processing, while the child frees the request/result queue +(so that the requests started before the fork will only be handled in the +parent). Threads will be started on demand until the limit set in the parent process has been reached again. In short: the parent will, after a short pause, continue as if fork had @@ -901,16 +1117,26 @@ =head2 MEMORY USAGE -Each aio request uses - depending on your architecture - around 128 bytes -of memory. In addition, stat requests need a stat buffer (possibly a few -hundred bytes). Perl scalars and other data passed into aio requests will -also be locked. +Per-request usage: + +Each aio request uses - depending on your architecture - around 100-200 +bytes of memory. In addition, stat requests need a stat buffer (possibly +a few hundred bytes), readdir requires a result buffer and so on. Perl +scalars and other data passed into aio requests will also be locked and +will consume memory till the request has entered the done state. This is now awfully much, so queuing lots of requests is not usually a problem. -Each thread needs a stack area which is usually around 16k, sometimes much -larger, depending on the OS. +Per-thread usage: + +In the execution phase, some aio requests require more memory for +temporary buffers, and each thread requires a stack and other data +structures (usually around 16k-128k, depending on the OS). + +=head1 KNOWN BUGS + +Known bugs will be fixed in the next release. =head1 SEE ALSO