--- Coro/Coro.pm 2008/11/19 05:52:42 1.224 +++ Coro/Coro.pm 2008/12/13 22:08:13 1.244 @@ -1,6 +1,6 @@ =head1 NAME -Coro - coroutine process abstraction +Coro - the only real threads in perl =head1 SYNOPSIS @@ -28,31 +28,38 @@ =head1 DESCRIPTION -This module collection manages coroutines. Coroutines are similar to -threads but don't (in general) run in parallel at the same time even -on SMP machines. The specific flavor of coroutine used in this module -also guarantees you that it will not switch between coroutines unless -necessary, at easily-identified points in your program, so locking and -parallel access are rarely an issue, making coroutine programming much -safer and easier than threads programming. - -Unlike a normal perl program, however, coroutines allow you to have -multiple running interpreters that share data, which is especially useful -to code pseudo-parallel processes and for event-based programming, such as -multiple HTTP-GET requests running concurrently. See L to -learn more. - -Coroutines are also useful because Perl has no support for threads (the so -called "threads" that perl offers are nothing more than the (bad) process -emulation coming from the Windows platform: On standard operating systems -they serve no purpose whatsoever, except by making your programs slow and -making them use a lot of memory. Best disable them when building perl, or -aks your software vendor/distributor to do it for you). +For a tutorial-style introduction, please read the L +manpage. This manpage mainly contains reference information. -In this module, coroutines are defined as "callchain + lexical variables + -@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain, +This module collection manages continuations in general, most often +in the form of cooperative threads (also called coroutines in the +documentation). They are similar to kernel threads but don't (in general) +run in parallel at the same time even on SMP machines. The specific flavor +of thread offered by this module also guarantees you that it will not +switch between threads unless necessary, at easily-identified points in +your program, so locking and parallel access are rarely an issue, making +thread programming much safer and easier than using other thread models. + +Unlike the so-called "Perl threads" (which are not actually real threads +but only the windows process emulation ported to unix), Coro provides a +full shared address space, which makes communication between threads +very easy. And threads are fast, too: disabling the Windows process +emulation code in your perl and using Coro can easily result in a two to +four times speed increase for your programs. + +Coro achieves that by supporting multiple running interpreters that share +data, which is especially useful to code pseudo-parallel processes and +for event-based programming, such as multiple HTTP-GET requests running +concurrently. See L to learn more on how to integrate Coro +into an event-based environment. + +In this module, a thread is defined as "callchain + lexical variables + +@_ + $_ + $@ + $/ + C stack), that is, a thread has its own callchain, its own set of lexicals and its own set of perls most important global -variables (see L for more configuration). +variables (see L for more configuration and background info). + +See also the C section at the end of this document - the Coro +module family is quite large. =cut @@ -69,7 +76,7 @@ our $main; # main coroutine our $current; # current coroutine -our $VERSION = 5.0; +our $VERSION = 5.13; our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); our %EXPORT_TAGS = ( @@ -77,6 +84,8 @@ ); our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); +=head1 GLOBAL VARIABLES + =over 4 =item $Coro::main @@ -107,22 +116,29 @@ =item $Coro::idle This variable is mainly useful to integrate Coro into event loops. It is -usually better to rely on L or LC, as this is +usually better to rely on L or L, as this is pretty low-level functionality. -This variable stores a callback that is called whenever the scheduler -finds no ready coroutines to run. The default implementation prints -"FATAL: deadlock detected" and exits, because the program has no other way -to continue. +This variable stores either a coroutine or a callback. -This hook is overwritten by modules such as C and +If it is a callback, the it is called whenever the scheduler finds no +ready coroutines to run. The default implementation prints "FATAL: +deadlock detected" and exits, because the program has no other way to +continue. + +If it is a coroutine object, then this object will be readied (without +invoking any ready hooks, however) when the scheduler finds no other ready +coroutines to run. + +This hook is overwritten by modules such as C and C to wait on an external event that hopefully wake up a coroutine so the scheduler can run it. Note that the callback I, under any circumstances, block the current coroutine. Normally, this is achieved by having an "idle coroutine" that calls the event loop and then blocks again, and then -readying that coroutine in the idle handler. +readying that coroutine in the idle handler, or by simply placing the idle +coroutine in this variable. See L or L for examples of using this technique. @@ -137,26 +153,14 @@ Carp::croak ("FATAL: deadlock detected"); }; -sub _cancel { - my ($self) = @_; - - # free coroutine data and mark as destructed - $self->_destroy - or return; - - # call all destruction callbacks - $_->(@{$self->{_status}}) - for @{ delete $self->{_on_destroy} || [] }; -} - # this coroutine is necessary because a coroutine # cannot destroy itself. -my @destroy; -my $manager; +our @destroy; +our $manager; $manager = new Coro sub { while () { - (shift @destroy)->_cancel + Coro::_cancel shift @destroy while @destroy; &schedule; @@ -167,13 +171,13 @@ =back -=head2 SIMPLE COROUTINE CREATION +=head1 SIMPLE COROUTINE CREATION =over 4 =item async { ... } [@args...] -Create a new coroutine and return it's coroutine object (usually +Create a new coroutine and return its coroutine object (usually unused). The coroutine will be put into the ready queue, so it will start running automatically on the next scheduler run. @@ -214,9 +218,9 @@ coroutine that might have executed other code already (which can be good or bad :). -On the plus side, this function is faster than creating (and destroying) -a completly new coroutine, so if you need a lot of generic coroutines in -quick successsion, use C, not C. +On the plus side, this function is about twice as fast as creating (and +destroying) a completely new coroutine, so if you need a lot of generic +coroutines in quick successsion, use C, not C. The code block is executed in an C context and a warning will be issued in case of an exception instead of terminating the program, as @@ -239,50 +243,31 @@ If you are concerned about pooled coroutines growing a lot because a single C used a lot of stackspace you can e.g. C once per second or so to slowly replenish the pool. In -addition to that, when the stacks used by a handler grows larger than 16kb +addition to that, when the stacks used by a handler grows larger than 32kb (adjustable via $Coro::POOL_RSS) it will also be destroyed. =cut our $POOL_SIZE = 8; -our $POOL_RSS = 16 * 1024; +our $POOL_RSS = 32 * 1024; our @async_pool; sub pool_handler { - my $cb; - while () { eval { - while () { - _pool_1 $cb; - &$cb; - _pool_2 $cb; - &schedule; - } + &{&_pool_handler} while 1; }; - if ($@) { - last if $@ eq "\3async_pool terminate\2\n"; - warn $@; - } + warn $@ if $@; } } -sub async_pool(&@) { - # this is also inlined into the unblock_scheduler - my $coro = (pop @async_pool) || new Coro \&pool_handler; - - $coro->{_invoke} = [@_]; - $coro->ready; - - $coro -} - =back -=head2 STATIC METHODS +=head1 STATIC METHODS -Static methods are actually functions that operate on the current coroutine. +Static methods are actually functions that implicitly operate on the +current coroutine. =over 4 @@ -341,10 +326,6 @@ =cut -sub terminate { - $current->cancel (@_); -} - sub killall { for (Coro::State::list) { $_->cancel @@ -354,7 +335,7 @@ =back -=head2 COROUTINE METHODS +=head1 COROUTINE OBJECT METHODS These are the methods you can call on coroutine objects (or to create them). @@ -373,16 +354,10 @@ =cut -sub _run_coro { +sub _coro_run { terminate &{+shift}; } -sub new { - my $class = shift; - - $class->SUPER::new (\&_run_coro, @_) -} - =item $success = $coroutine->ready Put the given coroutine into the end of its ready queue (there is one @@ -407,17 +382,34 @@ sub cancel { my $self = shift; - $self->{_status} = [@_]; if ($current == $self) { - push @destroy, $self; - $manager->ready; - &schedule while 1; + terminate @_; } else { + $self->{_status} = [@_]; $self->_cancel; } } +=item $coroutine->schedule_to + +Puts the current coroutine to sleep (like C), but instead +of continuing with the next coro from the ready queue, always switch to +the given coroutine object (regardless of priority etc.). The readyness +state of that coroutine isn't changed. + +This is an advanced method for special cases - I'd love to hear about any +uses for this one. + +=item $coroutine->cede_to + +Like C, but puts the current coroutine into the ready +queue. This has the effect of temporarily switching to the given +coroutine, and continuing some time later. + +This is an advanced method for special cases - I'd love to hear about any +uses for this one. + =item $coroutine->throw ([$scalar]) If C<$throw> is specified and defined, it will be thrown as an exception @@ -525,9 +517,14 @@ $old; } +sub transfer { + require Carp; + Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught"); +} + =back -=head2 GLOBAL FUNCTIONS +=head1 GLOBAL FUNCTIONS =over 4 @@ -542,37 +539,12 @@ =item my $guard = Coro::guard { ... } -This creates and returns a guard object. Nothing happens until the object -gets destroyed, in which case the codeblock given as argument will be -executed. This is useful to free locks or other resources in case of a -runtime error or when the coroutine gets canceled, as in both cases the -guard block will be executed. The guard object supports only one method, -C<< ->cancel >>, which will keep the codeblock from being executed. - -Example: set some flag and clear it again when the coroutine gets canceled -or the function returns: - - sub do_something { - my $guard = Coro::guard { $busy = 0 }; - $busy = 1; - - # do something that requires $busy to be true - } +This function still exists, but is deprecated. Please use the +C function instead. =cut -sub guard(&) { - bless \(my $cb = $_[0]), "Coro::guard" -} - -sub Coro::guard::cancel { - ${$_[0]} = sub { }; -} - -sub Coro::guard::DESTROY { - ${$_[0]}->(); -} - +BEGIN { *guard = \&Guard::guard } =item unblock_sub { ... } @@ -584,7 +556,7 @@ The reason this function exists is that many event libraries (such as the venerable L module) are not coroutine-safe (a weaker form -of thread-safety). This means you must not block within event callbacks, +of reentrancy). This means you must not block within event callbacks, otherwise you might suffer from crashes or worse. The only event library currently known that is safe to use without C is L. @@ -617,12 +589,12 @@ our $unblock_scheduler = new Coro sub { while () { while (my $cb = pop @unblock_queue) { - # this is an inlined copy of async_pool - my $coro = (pop @async_pool) || new Coro \&pool_handler; + &async_pool (@$cb); - $coro->{_invoke} = $cb; - $coro->ready; - cede; # for short-lived callbacks, this reduces pressure on the coro pool + # for short-lived callbacks, this reduces pressure on the coro pool + # as the chance is very high that the async_poll coro will be back + # in the idle state when cede returns + cede; } schedule; # sleep well } @@ -640,20 +612,20 @@ =item $cb = Coro::rouse_cb -Create and return a "rouse callback". That's a code reference that, when -called, will save its arguments and notify the owner coroutine of the -callback. +Create and return a "rouse callback". That's a code reference that, +when called, will remember a copy of its arguments and notify the owner +coroutine of the callback. See the next function. =item @args = Coro::rouse_wait [$cb] -Wait for the specified rouse callback (or the last one tht was created in +Wait for the specified rouse callback (or the last one that was created in this coroutine). -As soon as the callback is invoked (or when the calback was invoked before -C), it will return a copy of the arguments originally passed -to the rouse callback. +As soon as the callback is invoked (or when the callback was invoked +before C), it will return the arguments originally passed to +the rouse callback. See the section B for an actual usage example. @@ -686,7 +658,7 @@ C and C. The first function, C, generates and returns a callback that, -when invoked, will save it's arguments and notify the coroutine that +when invoked, will save its arguments and notify the coroutine that created the callback. The second function, C, waits for the callback to be called @@ -743,7 +715,7 @@ =item perl process emulation ("threads") This module is not perl-pseudo-thread-safe. You should only ever use this -module from the same thread (this requirement might be removed in the +module from the first thread (this requirement might be removed in the future to allow per-thread schedulers, but Coro::State does not yet allow this). I recommend disabling thread support and using processes, as having the windows process emulation enabled under unix roughly halves perl @@ -770,15 +742,18 @@ Support/Utility: L, L. -Locking/IPC: L, L, L, L, L. +Locking and IPC: L, L, L, +L, L. -IO/Timers: L, L, L, L. +I/O and Timers: L, L, L, L. -Compatibility: L, L, L, L. +Compatibility with other modules: L (but see also L for +a better-working alternative), L, L, +L. XS API: L. -Low level Configuration, Coroutine Environment: L. +Low level Configuration, Thread Environment, Continuations: L. =head1 AUTHOR