--- cvsroot/Coro/README 2008/11/25 20:48:41 1.20 +++ cvsroot/Coro/README 2008/12/15 20:52:04 1.21 @@ -11,7 +11,7 @@ print "4\n"; }; print "1\n"; - cede; # yield to coroutine + cede; # yield to coro print "3\n"; cede; # and again @@ -29,8 +29,8 @@ This manpage mainly contains reference information. 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 + the form of cooperative threads (also called coros, or simply "coro" 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 @@ -39,11 +39,14 @@ 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. + but only the windows process emulation ported to unix, and as such act + as processes), Coro provides a full shared address space, which makes + communication between threads very easy. And Coro's 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. A parallel matrix multiplication benchmark runs over 300 times + faster on a single core than perl's pseudo-threads on a quad core using + all four cores. Coro achieves that by supporting multiple running interpreters that share data, which is especially useful to code pseudo-parallel processes @@ -52,55 +55,55 @@ 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 Coro::State for more configuration and background info). + some package 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 Coro::State for more configuration and + background info). See also the "SEE ALSO" section at the end of this document - the Coro module family is quite large. GLOBAL VARIABLES $Coro::main - This variable stores the coroutine object that represents the main + This variable stores the Coro object that represents the main program. While you cna "ready" it and do most other things you can - do to coroutines, it is mainly useful to compare again - $Coro::current, to see whether you are running in the main program - or not. + do to coro, it is mainly useful to compare again $Coro::current, to + see whether you are running in the main program or not. $Coro::current - The coroutine object representing the current coroutine (the last - coroutine that the Coro scheduler switched to). The initial value is - $Coro::main (of course). + The Coro object representing the current coro (the last coro that + the Coro scheduler switched to). The initial value is $Coro::main + (of course). This variable is strictly *read-only*. You can take copies of the - value stored in it and use it as any other coroutine object, but you - must not otherwise modify the variable itself. + value stored in it and use it as any other Coro object, but you must + not otherwise modify the variable itself. $Coro::idle This variable is mainly useful to integrate Coro into event loops. It is usually better to rely on Coro::AnyEvent or Coro::EV, as this is pretty low-level functionality. - This variable stores either a coroutine or a callback. + This variable stores either a Coro object or a callback. 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. + no ready coros to run. The default implementation prints "FATAL: + deadlock detected" and exits, because the program has no other way + to continue. + + If it is a coro object, then this object will be readied (without + invoking any ready hooks, however) when the scheduler finds no other + ready coros to run. This hook is overwritten by modules such as "Coro::EV" and "Coro::AnyEvent" to wait on an external event that hopefully wake up - a coroutine so the scheduler can run it. + a coro so the scheduler can run it. Note that the callback *must not*, 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, or by simply placing - the idle coroutine in this variable. + the current coro. Normally, this is achieved by having an "idle + coro" that calls the event loop and then blocks again, and then + readying that coro in the idle handler, or by simply placing the + idle coro in this variable. See Coro::Event or Coro::AnyEvent for examples of using this technique. @@ -109,64 +112,63 @@ event handlers), then it must be prepared to be called recursively itself. -SIMPLE COROUTINE CREATION +SIMPLE CORO CREATION async { ... } [@args...] - 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. + Create a new coro and return its Coro object (usually unused). The + coro will be put into the ready queue, so it will start running + automatically on the next scheduler run. The first argument is a codeblock/closure that should be executed in - the coroutine. When it returns argument returns the coroutine is - automatically terminated. + the coro. When it returns argument returns the coro is automatically + terminated. The remaining arguments are passed as arguments to the closure. - See the "Coro::State::new" constructor for info about the coroutine - environment in which coroutines are executed. + See the "Coro::State::new" constructor for info about the coro + environment in which coro are executed. - Calling "exit" in a coroutine will do the same as calling exit - outside the coroutine. Likewise, when the coroutine dies, the - program will exit, just as it would in the main program. + Calling "exit" in a coro will do the same as calling exit outside + the coro. Likewise, when the coro dies, the program will exit, just + as it would in the main program. If you do not want that, you can provide a default "die" handler, or simply avoid dieing (by use of "eval"). - Example: Create a new coroutine that just prints its arguments. + Example: Create a new coro that just prints its arguments. async { print "@_\n"; } 1,2,3,4; async_pool { ... } [@args...] - Similar to "async", but uses a coroutine pool, so you should not - call terminate or join on it (although you are allowed to), and you - get a coroutine that might have executed other code already (which - can be good or bad :). + Similar to "async", but uses a coro pool, so you should not call + terminate or join on it (although you are allowed to), and you get a + coro that might have executed other code already (which can be good + or bad :). 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 "async_pool", not - "async". + (and destroying) a completely new coro, so if you need a lot of + generic coros in quick successsion, use "async_pool", not "async". The code block is executed in an "eval" context and a warning will be issued in case of an exception instead of terminating the - program, as "async" does. As the coroutine is being reused, stuff - like "on_destroy" will not work in the expected way, unless you call + program, as "async" does. As the coro is being reused, stuff like + "on_destroy" will not work in the expected way, unless you call terminate or cancel, which somehow defeats the purpose of pooling (but is fine in the exceptional case). The priority will be reset to 0 after each run, tracing will be disabled, the description will be reset and the default output filehandle gets restored, so you can change all these. Otherwise the - coroutine will be re-used "as-is": most notably if you change other - per-coroutine global stuff such as $/ you *must needs* revert that + coro will be re-used "as-is": most notably if you change other + per-coro global stuff such as $/ you *must needs* revert that change, which is most simply done by using local as in: "local $/". - The idle pool size is limited to 8 idle coroutines (this can be - adjusted by changing $Coro::POOL_SIZE), but there can be as many - non-idle coros as required. + The idle pool size is limited to 8 idle coros (this can be adjusted + by changing $Coro::POOL_SIZE), but there can be as many non-idle + coros as required. - If you are concerned about pooled coroutines growing a lot because a + If you are concerned about pooled coros growing a lot because a single "async_pool" used a lot of stackspace you can e.g. "async_pool { terminate }" once per second or so to slowly replenish the pool. In addition to that, when the stacks used by a handler @@ -175,110 +177,174 @@ STATIC METHODS Static methods are actually functions that implicitly operate on the - current coroutine. + current coro. schedule - Calls the scheduler. The scheduler will find the next coroutine that - is to be run from the ready queue and switches to it. The next - coroutine to be run is simply the one with the highest priority that - is longest in its ready queue. If there is no coroutine ready, it - will clal the $Coro::idle hook. - - Please note that the current coroutine will *not* be put into the - ready queue, so calling this function usually means you will never - be called again unless something else (e.g. an event handler) calls + Calls the scheduler. The scheduler will find the next coro that is + to be run from the ready queue and switches to it. The next coro to + be run is simply the one with the highest priority that is longest + in its ready queue. If there is no coro ready, it will clal the + $Coro::idle hook. + + Please note that the current coro will *not* be put into the ready + queue, so calling this function usually means you will never be + called again unless something else (e.g. an event handler) calls "->ready", thus waking you up. This makes "schedule" *the* generic method to use to block the - current coroutine and wait for events: first you remember the - current coroutine in a variable, then arrange for some callback of - yours to call "->ready" on that once some event happens, and last - you call "schedule" to put yourself to sleep. Note that a lot of - things can wake your coroutine up, so you need to check whether the - event indeed happened, e.g. by storing the status in a variable. + current coro and wait for events: first you remember the current + coro in a variable, then arrange for some callback of yours to call + "->ready" on that once some event happens, and last you call + "schedule" to put yourself to sleep. Note that a lot of things can + wake your coro up, so you need to check whether the event indeed + happened, e.g. by storing the status in a variable. See HOW TO WAIT FOR A CALLBACK, below, for some ways to wait for callbacks. cede - "Cede" to other coroutines. This function puts the current coroutine - into the ready queue and calls "schedule", which has the effect of - giving up the current "timeslice" to other coroutines of the same or - higher priority. Once your coroutine gets its turn again it will - automatically be resumed. + "Cede" to other coros. This function puts the current coro into the + ready queue and calls "schedule", which has the effect of giving up + the current "timeslice" to other coros of the same or higher + priority. Once your coro gets its turn again it will automatically + be resumed. This function is often called "yield" in other languages. Coro::cede_notself Works like cede, but is not exported by default and will cede to - *any* coroutine, regardless of priority. This is useful sometimes to + *any* coro, regardless of priority. This is useful sometimes to ensure progress is made. terminate [arg...] - Terminates the current coroutine with the given status values (see + Terminates the current coro with the given status values (see cancel). + Coro::on_enter BLOCK, Coro::on_leave BLOCK + These function install enter and leave winders in the current scope. + The enter block will be executed when on_enter is called and + whenever the current coro is re-entered by the scheduler, while the + leave block is executed whenever the current coro is blocked by the + scheduler, and also when the containing scope is exited (by whatever + means, be it exit, die, last etc.). + + *Neither invoking the scheduler, nor exceptions, are allowed within + those BLOCKs*. That means: do not even think about calling "die" + without an eval, and do not even think of entering the scheduler in + any way. + + Since both BLOCKs are tied to the current scope, they will + automatically be removed when the current scope exits. + + These functions implement the same concept as "dynamic-wind" in + scheme does, and are useful when you want to localise some resource + to a specific coro. + + They slow down coro switching considerably for coros that use them + (But coro switching is still reasonably fast if the handlers are + fast). + + These functions are best understood by an example: The following + function will change the current timezone to + "Antarctica/South_Pole", which requires a call to "tzset", but by + using "on_enter" and "on_leave", which remember/change the current + timezone and restore the previous value, respectively, the timezone + is only changes for the coro that installed those handlers. + + use POSIX qw(tzset); + + async { + my $old_tz; # store outside TZ value here + + Coro::on_enter { + $old_tz = $ENV{TZ}; # remember the old value + + $ENV{TZ} = "Antarctica/South_Pole"; + tzset; # enable new value + }; + + Coro::on_leave { + $ENV{TZ} = $old_tz; + tzset; # restore old value + }; + + # at this place, the timezone is Antarctica/South_Pole, + # without disturbing the TZ of any other coro. + }; + + This can be used to localise about any resource (locale, uid, + current working directory etc.) to a block, despite the existance of + other coros. + killall - Kills/terminates/cancels all coroutines except the currently running - one. This is useful after a fork, either in the child or the parent, - as usually only one of them should inherit the running coroutines. - - Note that while this will try to free some of the main programs - resources, you cannot free all of them, so if a coroutine that is - not the main program calls this function, there will be some - one-time resource leak. - -COROUTINE OBJECT METHODS - These are the methods you can call on coroutine objects (or to create - them). + Kills/terminates/cancels all coros except the currently running one. + + Note that while this will try to free some of the main interpreter + resources if the calling coro isn't the main coro, but one cannot + free all of them, so if a coro that is not the main coro calls this + function, there will be some one-time resource leak. + +CORO OBJECT METHODS + These are the methods you can call on coro objects (or to create them). new Coro \&sub [, @args...] - Create a new coroutine and return it. When the sub returns, the - coroutine automatically terminates as if "terminate" with the - returned values were called. To make the coroutine run you must - first put it into the ready queue by calling the ready method. + Create a new coro and return it. When the sub returns, the coro + automatically terminates as if "terminate" with the returned values + were called. To make the coro run you must first put it into the + ready queue by calling the ready method. See "async" and "Coro::State::new" for additional info about the - coroutine environment. + coro environment. - $success = $coroutine->ready - Put the given coroutine into the end of its ready queue (there is - one queue for each priority) and return true. If the coroutine is - already in the ready queue, do nothing and return false. - - This ensures that the scheduler will resume this coroutine - automatically once all the coroutines of higher priority and all - coroutines of the same priority that were put into the ready queue - earlier have been resumed. - - $is_ready = $coroutine->is_ready - Return whether the coroutine is currently the ready queue or not, - - $coroutine->cancel (arg...) - Terminates the given coroutine and makes it return the given - arguments as status (default: the empty list). Never returns if the - coroutine is the current coroutine. - - $coroutine->schedule_to - Puts the current coroutine to sleep (like "Coro::schedule"), 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. + $success = $coro->ready + Put the given coro into the end of its ready queue (there is one + queue for each priority) and return true. If the coro is already in + the ready queue, do nothing and return false. + + This ensures that the scheduler will resume this coro automatically + once all the coro of higher priority and all coro of the same + priority that were put into the ready queue earlier have been + resumed. + + $is_ready = $coro->is_ready + Returns true iff the Coro object is in the ready queue. Unless the + Coro object gets destroyed, it will eventually be scheduled by the + scheduler. + + $is_running = $coro->is_running + Returns true iff the Coro object is currently running. Only one Coro + object can ever be in the running state (but it currently is + possible to have multiple running Coro::States). + + $is_suspended = $coro->is_suspended + Returns true iff this Coro object has been suspended. Suspended + Coros will not ever be scheduled. + + $coro->cancel (arg...) + Terminates the given Coro and makes it return the given arguments as + status (default: the empty list). Never returns if the Coro is the + current Coro. + + $coro->schedule_to + Puts the current coro to sleep (like "Coro::schedule"), but instead + of continuing with the next coro from the ready queue, always switch + to the given coro object (regardless of priority etc.). The + readyness state of that coro isn't changed. This is an advanced method for special cases - I'd love to hear about any uses for this one. - $coroutine->cede_to - Like "schedule_to", 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. + $coro->cede_to + Like "schedule_to", but puts the current coro into the ready queue. + This has the effect of temporarily switching to the given coro, and + continuing some time later. This is an advanced method for special cases - I'd love to hear about any uses for this one. - $coroutine->throw ([$scalar]) + $coro->throw ([$scalar]) If $throw is specified and defined, it will be thrown as an - exception inside the coroutine at the next convenient point in time. + exception inside the coro at the next convenient point in time. Otherwise clears the exception object. Coro will check for the exception each time a schedule-like-function @@ -291,113 +357,95 @@ scalar in $@, i.e. if it is a string, no line number or newline will be appended (unlike with "die"). - This can be used as a softer means than "cancel" to ask a coroutine - to end itself, although there is no guarantee that the exception - will lead to termination, and if the exception isn't caught it might - well end the whole program. + This can be used as a softer means than "cancel" to ask a coro to + end itself, although there is no guarantee that the exception will + lead to termination, and if the exception isn't caught it might well + end the whole program. You might also think of "throw" as being the moral equivalent of - "kill"ing a coroutine with a signal (in this case, a scalar). + "kill"ing a coro with a signal (in this case, a scalar). - $coroutine->join - Wait until the coroutine terminates and return any values given to - the "terminate" or "cancel" functions. "join" can be called - concurrently from multiple coroutines, and all will be resumed and - given the status return once the $coroutine terminates. - - $coroutine->on_destroy (\&cb) - Registers a callback that is called when this coroutine gets - destroyed, but before it is joined. The callback gets passed the - terminate arguments, if any, and *must not* die, under any - circumstances. - - $oldprio = $coroutine->prio ($newprio) - Sets (or gets, if the argument is missing) the priority of the - coroutine. Higher priority coroutines get run before lower priority - coroutines. Priorities are small signed integers (currently -4 .. - +3), that you can refer to using PRIO_xxx constants (use the import - tag :prio to get then): + $coro->join + Wait until the coro terminates and return any values given to the + "terminate" or "cancel" functions. "join" can be called concurrently + from multiple coro, and all will be resumed and given the status + return once the $coro terminates. + + $coro->on_destroy (\&cb) + Registers a callback that is called when this coro gets destroyed, + but before it is joined. The callback gets passed the terminate + arguments, if any, and *must not* die, under any circumstances. + + $oldprio = $coro->prio ($newprio) + Sets (or gets, if the argument is missing) the priority of the coro. + Higher priority coro get run before lower priority coro. Priorities + are small signed integers (currently -4 .. +3), that you can refer + to using PRIO_xxx constants (use the import tag :prio to get then): PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 3 > 1 > 0 > -1 > -3 > -4 # set priority to HIGH - current->prio(PRIO_HIGH); + current->prio (PRIO_HIGH); - The idle coroutine ($Coro::idle) always has a lower priority than - any existing coroutine. + The idle coro ($Coro::idle) always has a lower priority than any + existing coro. - Changing the priority of the current coroutine will take effect - immediately, but changing the priority of coroutines in the ready - queue (but not running) will only take effect after the next - schedule (of that coroutine). This is a bug that will be fixed in - some future version. + Changing the priority of the current coro will take effect + immediately, but changing the priority of coro in the ready queue + (but not running) will only take effect after the next schedule (of + that coro). This is a bug that will be fixed in some future version. - $newprio = $coroutine->nice ($change) + $newprio = $coro->nice ($change) Similar to "prio", but subtract the given value from the priority (i.e. higher values mean lower priority, just as in unix). - $olddesc = $coroutine->desc ($newdesc) + $olddesc = $coro->desc ($newdesc) Sets (or gets in case the argument is missing) the description for - this coroutine. This is just a free-form string you can associate - with a coroutine. + this coro. This is just a free-form string you can associate with a + coro. - This method simply sets the "$coroutine->{desc}" member to the given + This method simply sets the "$coro->{desc}" member to the given string. You can modify this member directly if you wish. GLOBAL FUNCTIONS Coro::nready - Returns the number of coroutines that are currently in the ready - state, i.e. that can be switched to by calling "schedule" directory - or indirectly. The value 0 means that the only runnable coroutine is - the currently running one, so "cede" would have no effect, and + Returns the number of coro that are currently in the ready state, + i.e. that can be switched to by calling "schedule" directory or + indirectly. The value 0 means that the only runnable coro is the + currently running one, so "cede" would have no effect, and "schedule" would cause a deadlock unless there is an idle handler - that wakes up some coroutines. + that wakes up some coro. 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, "->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 + "Guard::guard" function instead. unblock_sub { ... } This utility function takes a BLOCK or code reference and "unblocks" it, returning a new coderef. Unblocking means that calling the new coderef will return immediately without blocking, returning nothing, while the original code ref will be called (with parameters) from - within another coroutine. + within another coro. The reason this function exists is that many event libraries (such - as the venerable Event module) are not coroutine-safe (a weaker form - 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 - "unblock_sub" is EV. + as the venerable Event module) are not thread-safe (a weaker form 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 "unblock_sub" is + EV. This function allows your callbacks to block by executing them in - another coroutine where it is safe to block. One example where - blocking is handy is when you use the Coro::AIO functions to save - results to disk, for example. + another coro where it is safe to block. One example where blocking + is handy is when you use the Coro::AIO functions to save results to + disk, for example. In short: simply use "unblock_sub { ... }" instead of "sub { ... }" when creating event callbacks that want to block. If your handler does not plan to block (e.g. simply sends a message - to another coroutine, or puts some other coroutine into the ready - queue), there is no reason to use "unblock_sub". + to another coro, or puts some other coro into the ready queue), + there is no reason to use "unblock_sub". Note that you also need to use "unblock_sub" for any other callbacks that are indirectly executed by any C-based event loop. For example, @@ -409,13 +457,13 @@ $cb = Coro::rouse_cb Create and return a "rouse callback". That's a code reference that, when called, will remember a copy of its arguments and notify the - owner coroutine of the callback. + owner coro of the callback. See the next function. @args = Coro::rouse_wait [$cb] Wait for the specified rouse callback (or the last one that was - created in this coroutine). + created in this coro). As soon as the callback is invoked (or when the callback was invoked before "rouse_wait"), it will return the arguments originally passed @@ -425,20 +473,20 @@ example. HOW TO WAIT FOR A CALLBACK - It is very common for a coroutine to wait for some callback to be - called. This occurs naturally when you use coroutines in an otherwise - event-based program, or when you use event-based libraries. + It is very common for a coro to wait for some callback to be called. + This occurs naturally when you use coro in an otherwise event-based + program, or when you use event-based libraries. These typically register a callback for some event, and call that - callback when the event occured. In a coroutine, however, you typically - want to just wait for the event, simplyifying things. + callback when the event occured. In a coro, however, you typically want + to just wait for the event, simplyifying things. For example "AnyEvent->child" registers a callback to be called when a specific child has exited: my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... }); - But from withina coroutine, you often just want to write this: + But from within a coro, you often just want to write this: my $status = wait_for_child $pid; @@ -446,8 +494,8 @@ "Coro::rouse_cb" and "Coro::rouse_wait". The first function, "rouse_cb", generates and returns a callback that, - when invoked, will save its arguments and notify the coroutine that - created the callback. + when invoked, will save its arguments and notify the coro that created + the callback. The second function, "rouse_wait", waits for the callback to be called (by calling "schedule" to go to sleep) and returns the arguments @@ -471,7 +519,7 @@ sub wait_for_child($) { my ($pid) = @_; - # store the current coroutine in $current, + # store the current coro in $current, # and provide result variables for the closure passed to ->child my $current = $Coro::current; my ($done, $rstatus); @@ -492,7 +540,7 @@ fork with pthread backend When Coro is compiled using the pthread backend (which isn't recommended but required on many BSDs as their libcs are completely - broken), then coroutines will not survive a fork. There is no known + broken), then coro will not survive a fork. There is no known workaround except to fix your libc and use a saner backend. perl process emulation ("threads") @@ -503,13 +551,13 @@ processes, as having the windows process emulation enabled under unix roughly halves perl performance, even when not used. - coroutine switching not signal safe - You must not switch to another coroutine from within a signal - handler (only relevant with %SIG - most event libraries provide safe + coro switching is not signal safe + You must not switch to another coro from within a signal handler + (only relevant with %SIG - most event libraries provide safe signals). That means you *MUST NOT* call any function that might "block" the - current coroutine - "cede", "schedule" "Coro::Semaphore->down" or + current coro - "cede", "schedule" "Coro::Semaphore->down" or anything that calls those. Everything else, including calling "ready", works.