[ViewVC] Diff of: cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.187 by root, Mon Sep 29 03:31:14 2008 UTC vs.
Revision 1.197 by root, Tue Oct 21 20:52:30 2008 UTC

…		…
685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
687		687
688	This "unloop state" will be cleared when entering C<ev_loop> again.	688	This "unloop state" will be cleared when entering C<ev_loop> again.
689		689
		690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		691
690	=item ev_ref (loop)	692	=item ev_ref (loop)
691		693
692	=item ev_unref (loop)	694	=item ev_unref (loop)
693		695
694	Ref/unref can be used to add or remove a reference count on the event	696	Ref/unref can be used to add or remove a reference count on the event
…		…
892	=item C<EV_ERROR>	894	=item C<EV_ERROR>
893		895
894	An unspecified error has occurred, the watcher has been stopped. This might	896	An unspecified error has occurred, the watcher has been stopped. This might
895	happen because the watcher could not be properly started because libev	897	happen because the watcher could not be properly started because libev
896	ran out of memory, a file descriptor was found to be closed or any other	898	ran out of memory, a file descriptor was found to be closed or any other
		899	problem. Libev considers these application bugs.
		900
897	problem. You best act on it by reporting the problem and somehow coping	901	You best act on it by reporting the problem and somehow coping with the
898	with the watcher being stopped.	902	watcher being stopped. Note that well-written programs should not receive
		903	an error ever, so when your watcher receives it, this usually indicates a
		904	bug in your program.
899		905
900	Libev will usually signal a few "dummy" events together with an error, for	906	Libev will usually signal a few "dummy" events together with an error, for
901	example it might indicate that a fd is readable or writable, and if your	907	example it might indicate that a fd is readable or writable, and if your
902	callbacks is well-written it can just attempt the operation and cope with	908	callbacks is well-written it can just attempt the operation and cope with
903	the error from read() or write(). This will not work in multi-threaded	909	the error from read() or write(). This will not work in multi-threaded
…		…
967		973
968	ev_io_start (EV_DEFAULT_UC, &w);	974	ev_io_start (EV_DEFAULT_UC, &w);
969		975
970	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)	976	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)
971		977
972	Stops the given watcher again (if active) and clears the pending	978	Stops the given watcher if active, and clears the pending status (whether
		979	the watcher was active or not).
		980
973	status. It is possible that stopped watchers are pending (for example,	981	It is possible that stopped watchers are pending - for example,
974	non-repeating timers are being stopped when they become pending), but	982	non-repeating timers are being stopped when they become pending - but
975	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	983	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
976	you want to free or reuse the memory used by the watcher it is therefore a	984	pending. If you want to free or reuse the memory used by the watcher it is
977	good idea to always call its C<ev_TYPE_stop> function.	985	therefore a good idea to always call its C<ev_TYPE_stop> function.
978		986
979	=item bool ev_is_active (ev_TYPE *watcher)	987	=item bool ev_is_active (ev_TYPE *watcher)
980		988
981	Returns a true value iff the watcher is active (i.e. it has been started	989	Returns a true value iff the watcher is active (i.e. it has been started
982	and not yet been stopped). As long as a watcher is active you must not modify	990	and not yet been stopped). As long as a watcher is active you must not modify
…		…
1625		1633
1626	=back	1634	=back
1627		1635
1628	=head3 Examples	1636	=head3 Examples
1629		1637
1630	Example: Try to exit cleanly on SIGINT and SIGTERM.	1638	Example: Try to exit cleanly on SIGINT.
1631		1639
1632	static void	1640	static void
1633	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1641	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
1634	{	1642	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	1643	ev_unloop (loop, EVUNLOOP_ALL);
1636	}	1644	}
1637		1645
1638	struct ev_signal signal_watcher;	1646	struct ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1647	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &sigint_cb);	1648	ev_signal_start (loop, &signal_watcher);
1641		1649
1642		1650
1643	=head2 C<ev_child> - watch out for process status changes	1651	=head2 C<ev_child> - watch out for process status changes
1644		1652
1645	Child watchers trigger when your process receives a SIGCHLD in response to	1653	Child watchers trigger when your process receives a SIGCHLD in response to
…		…
1792	to exchange stat structures with application programs compiled using the	1800	to exchange stat structures with application programs compiled using the
1793	default compilation environment.	1801	default compilation environment.
1794		1802
1795	=head3 Inotify and Kqueue	1803	=head3 Inotify and Kqueue
1796		1804
1797	When C<inotify (7)> support has been compiled into libev (generally only	1805	When C<inotify (7)> support has been compiled into libev (generally
		1806	only available with Linux 2.6.25 or above due to bugs in earlier
1798	available with Linux) and present at runtime, it will be used to speed up	1807	implementations) and present at runtime, it will be used to speed up
1799	change detection where possible. The inotify descriptor will be created lazily	1808	change detection where possible. The inotify descriptor will be created
1800	when the first C<ev_stat> watcher is being started.	1809	lazily when the first C<ev_stat> watcher is being started.
1801		1810
1802	Inotify presence does not change the semantics of C<ev_stat> watchers	1811	Inotify presence does not change the semantics of C<ev_stat> watchers
1803	except that changes might be detected earlier, and in some cases, to avoid	1812	except that changes might be detected earlier, and in some cases, to avoid
1804	making regular C<stat> calls. Even in the presence of inotify support	1813	making regular C<stat> calls. Even in the presence of inotify support
1805	there are many cases where libev has to resort to regular C<stat> polling,	1814	there are many cases where libev has to resort to regular C<stat> polling,
…		…
2384	=over 4	2393	=over 4
2385		2394
2386	=item queueing from a signal handler context	2395	=item queueing from a signal handler context
2387		2396
2388	To implement race-free queueing, you simply add to the queue in the signal	2397	To implement race-free queueing, you simply add to the queue in the signal
2389	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2398	handler but you block the signal handler in the watcher callback. Here is
2390	some fictitious SIGUSR1 handler:	2399	an example that does that for some fictitious SIGUSR1 handler:
2391		2400
2392	static ev_async mysig;	2401	static ev_async mysig;
2393		2402
2394	static void	2403	static void
2395	sigusr1_handler (void)	2404	sigusr1_handler (void)
…		…
2502	=over 4	2511	=over 4
2503		2512
2504	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2513	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2505		2514
2506	This function combines a simple timer and an I/O watcher, calls your	2515	This function combines a simple timer and an I/O watcher, calls your
2507	callback on whichever event happens first and automatically stop both	2516	callback on whichever event happens first and automatically stops both
2508	watchers. This is useful if you want to wait for a single event on an fd	2517	watchers. This is useful if you want to wait for a single event on an fd
2509	or timeout without having to allocate/configure/start/stop/free one or	2518	or timeout without having to allocate/configure/start/stop/free one or
2510	more watchers yourself.	2519	more watchers yourself.
2511		2520
2512	If C<fd> is less than 0, then no I/O watcher will be started and events	2521	If C<fd> is less than 0, then no I/O watcher will be started and the
2513	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2522	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2514	C<events> set will be created and started.	2523	the given C<fd> and C<events> set will be created and started.
2515		2524
2516	If C<timeout> is less than 0, then no timeout watcher will be	2525	If C<timeout> is less than 0, then no timeout watcher will be
2517	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2526	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2518	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2527	repeat = 0) will be started. C<0> is a valid timeout.
2519	dubious value.
2520		2528
2521	The callback has the type C<void (cb)(int revents, void arg)> and gets	2529	The callback has the type C<void (cb)(int revents, void arg)> and gets
2522	passed an C<revents> set like normal event callbacks (a combination of	2530	passed an C<revents> set like normal event callbacks (a combination of
2523	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2531	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2524	value passed to C<ev_once>:	2532	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2533	a timeout and an io event at the same time - you probably should give io
		2534	events precedence.
		2535
		2536	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2525		2537
2526	static void stdin_ready (int revents, void *arg)	2538	static void stdin_ready (int revents, void *arg)
2527	{	2539	{
		2540	if (revents & EV_READ)
		2541	/* stdin might have data for us, joy! */;
2528	if (revents & EV_TIMEOUT)	2542	else if (revents & EV_TIMEOUT)
2529	/* doh, nothing entered */;	2543	/* doh, nothing entered */;
2530	else if (revents & EV_READ)
2531	/* stdin might have data for us, joy! */;
2532	}	2544	}
2533		2545
2534	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2546	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2535		2547
2536	=item ev_feed_event (ev_loop , watcher , int revents)	2548	=item ev_feed_event (ev_loop , watcher , int revents)
…		…
3306	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3318	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3307		3319
3308	#include "ev_cpp.h"	3320	#include "ev_cpp.h"
3309	#include "ev.c"	3321	#include "ev.c"
3310		3322
		3323	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3311		3324
3312	=head1 THREADS AND COROUTINES	3325	=head2 THREADS AND COROUTINES
3313		3326
3314	=head2 THREADS	3327	=head3 THREADS
3315		3328
3316	All libev functions are reentrant and thread-safe unless explicitly	3329	All libev functions are reentrant and thread-safe unless explicitly
3317	documented otherwise, but it uses no locking itself. This means that you	3330	documented otherwise, but libev implements no locking itself. This means
3318	can use as many loops as you want in parallel, as long as there are no	3331	that you can use as many loops as you want in parallel, as long as there
3319	concurrent calls into any libev function with the same loop parameter	3332	are no concurrent calls into any libev function with the same loop
3320	(C<ev_default_*> calls have an implicit default loop parameter, of	3333	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3321	course): libev guarantees that different event loops share no data	3334	of course): libev guarantees that different event loops share no data
3322	structures that need any locking.	3335	structures that need any locking.
3323		3336
3324	Or to put it differently: calls with different loop parameters can be done	3337	Or to put it differently: calls with different loop parameters can be done
3325	concurrently from multiple threads, calls with the same loop parameter	3338	concurrently from multiple threads, calls with the same loop parameter
3326	must be done serially (but can be done from different threads, as long as	3339	must be done serially (but can be done from different threads, as long as
…		…
3366	default loop and triggering an C<ev_async> watcher from the default loop	3379	default loop and triggering an C<ev_async> watcher from the default loop
3367	watcher callback into the event loop interested in the signal.	3380	watcher callback into the event loop interested in the signal.
3368		3381
3369	=back	3382	=back
3370		3383
3371	=head2 COROUTINES	3384	=head3 COROUTINES
3372		3385
3373	Libev is much more accommodating to coroutines ("cooperative threads"):	3386	Libev is very accommodating to coroutines ("cooperative threads"):
3374	libev fully supports nesting calls to it's functions from different	3387	libev fully supports nesting calls to its functions from different
3375	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3388	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3376	different coroutines and switch freely between both coroutines running the	3389	different coroutines, and switch freely between both coroutines running the
3377	loop, as long as you don't confuse yourself). The only exception is that	3390	loop, as long as you don't confuse yourself). The only exception is that
3378	you must not do this from C<ev_periodic> reschedule callbacks.	3391	you must not do this from C<ev_periodic> reschedule callbacks.
3379		3392
3380	Care has been taken to ensure that libev does not keep local state inside	3393	Care has been taken to ensure that libev does not keep local state inside
3381	C<ev_loop>, and other calls do not usually allow coroutine switches.	3394	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3395	they do not clal any callbacks.
3382		3396
		3397	=head2 COMPILER WARNINGS
3383		3398
3384	=head1 COMPLEXITIES	3399	Depending on your compiler and compiler settings, you might get no or a
		3400	lot of warnings when compiling libev code. Some people are apparently
		3401	scared by this.
3385		3402
3386	In this section the complexities of (many of) the algorithms used inside	3403	However, these are unavoidable for many reasons. For one, each compiler
3387	libev will be explained. For complexity discussions about backends see the	3404	has different warnings, and each user has different tastes regarding
3388	documentation for C<ev_default_init>.	3405	warning options. "Warn-free" code therefore cannot be a goal except when
		3406	targeting a specific compiler and compiler-version.
3389		3407
3390	All of the following are about amortised time: If an array needs to be	3408	Another reason is that some compiler warnings require elaborate
3391	extended, libev needs to realloc and move the whole array, but this	3409	workarounds, or other changes to the code that make it less clear and less
3392	happens asymptotically never with higher number of elements, so O(1) might	3410	maintainable.
3393	mean it might do a lengthy realloc operation in rare cases, but on average
3394	it is much faster and asymptotically approaches constant time.
3395		3411
3396	=over 4	3412	And of course, some compiler warnings are just plain stupid, or simply
		3413	wrong (because they don't actually warn about the condition their message
		3414	seems to warn about). For example, certain older gcc versions had some
		3415	warnings that resulted an extreme number of false positives. These have
		3416	been fixed, but some people still insist on making code warn-free with
		3417	such buggy versions.
3397		3418
3398	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3419	While libev is written to generate as few warnings as possible,
		3420	"warn-free" code is not a goal, and it is recommended not to build libev
		3421	with any compiler warnings enabled unless you are prepared to cope with
		3422	them (e.g. by ignoring them). Remember that warnings are just that:
		3423	warnings, not errors, or proof of bugs.
3399		3424
3400	This means that, when you have a watcher that triggers in one hour and
3401	there are 100 watchers that would trigger before that then inserting will
3402	have to skip roughly seven (C<ld 100>) of these watchers.
3403		3425
3404	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3426	=head2 VALGRIND
3405		3427
3406	That means that changing a timer costs less than removing/adding them	3428	Valgrind has a special section here because it is a popular tool that is
3407	as only the relative motion in the event queue has to be paid for.	3429	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3408		3430
3409	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3431	If you think you found a bug (memory leak, uninitialised data access etc.)
		3432	in libev, then check twice: If valgrind reports something like:
3410		3433
3411	These just add the watcher into an array or at the head of a list.	3434	==2274== definitely lost: 0 bytes in 0 blocks.
		3435	==2274== possibly lost: 0 bytes in 0 blocks.
		3436	==2274== still reachable: 256 bytes in 1 blocks.
3412		3437
3413	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3438	Then there is no memory leak, just as memory accounted to global variables
		3439	is not a memleak - the memory is still being refernced, and didn't leak.
3414		3440
3415	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3441	Similarly, under some circumstances, valgrind might report kernel bugs
		3442	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3443	although an acceptable workaround has been found here), or it might be
		3444	confused.
3416		3445
3417	These watchers are stored in lists then need to be walked to find the	3446	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3418	correct watcher to remove. The lists are usually short (you don't usually	3447	make it into some kind of religion.
3419	have many watchers waiting for the same fd or signal).
3420		3448
3421	=item Finding the next timer in each loop iteration: O(1)	3449	If you are unsure about something, feel free to contact the mailing list
		3450	with the full valgrind report and an explanation on why you think this
		3451	is a bug in libev (best check the archives, too :). However, don't be
		3452	annoyed when you get a brisk "this is no bug" answer and take the chance
		3453	of learning how to interpret valgrind properly.
3422		3454
3423	By virtue of using a binary or 4-heap, the next timer is always found at a	3455	If you need, for some reason, empty reports from valgrind for your project
3424	fixed position in the storage array.	3456	I suggest using suppression lists.
3425		3457
3426	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3427		3458
3428	A change means an I/O watcher gets started or stopped, which requires	3459	=head1 PORTABILITY NOTES
3429	libev to recalculate its status (and possibly tell the kernel, depending
3430	on backend and whether C<ev_io_set> was used).
3431		3460
3432	=item Activating one watcher (putting it into the pending state): O(1)
3433
3434	=item Priority handling: O(number_of_priorities)
3435
3436	Priorities are implemented by allocating some space for each
3437	priority. When doing priority-based operations, libev usually has to
3438	linearly search all the priorities, but starting/stopping and activating
3439	watchers becomes O(1) with respect to priority handling.
3440
3441	=item Sending an ev_async: O(1)
3442
3443	=item Processing ev_async_send: O(number_of_async_watchers)
3444
3445	=item Processing signals: O(max_signal_number)
3446
3447	Sending involves a system call I<iff> there were no other C<ev_async_send>
3448	calls in the current loop iteration. Checking for async and signal events
3449	involves iterating over all running async watchers or all signal numbers.
3450
3451	=back
3452
3453
3454	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3461	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3455		3462
3456	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3463	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3457	requires, and its I/O model is fundamentally incompatible with the POSIX	3464	requires, and its I/O model is fundamentally incompatible with the POSIX
3458	model. Libev still offers limited functionality on this platform in	3465	model. Libev still offers limited functionality on this platform in
3459	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3466	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3546	wrap all I/O functions and provide your own fd management, but the cost of	3553	wrap all I/O functions and provide your own fd management, but the cost of
3547	calling select (O(n²)) will likely make this unworkable.	3554	calling select (O(n²)) will likely make this unworkable.
3548		3555
3549	=back	3556	=back
3550		3557
3551
3552	=head1 PORTABILITY REQUIREMENTS	3558	=head2 PORTABILITY REQUIREMENTS
3553		3559
3554	In addition to a working ISO-C implementation, libev relies on a few	3560	In addition to a working ISO-C implementation and of course the
3555	additional extensions:	3561	backend-specific APIs, libev relies on a few additional extensions:
3556		3562
3557	=over 4	3563	=over 4
3558		3564
3559	=item C<void ()(ev_watcher_type , int revents)> must have compatible	3565	=item C<void ()(ev_watcher_type , int revents)> must have compatible
3560	calling conventions regardless of C<ev_watcher_type *>.	3566	calling conventions regardless of C<ev_watcher_type *>.
…		…
3585	except the initial one, and run the default loop in the initial thread as	3591	except the initial one, and run the default loop in the initial thread as
3586	well.	3592	well.
3587		3593
3588	=item C<long> must be large enough for common memory allocation sizes	3594	=item C<long> must be large enough for common memory allocation sizes
3589		3595
3590	To improve portability and simplify using libev, libev uses C<long>	3596	To improve portability and simplify its API, libev uses C<long> internally
3591	internally instead of C<size_t> when allocating its data structures. On	3597	instead of C<size_t> when allocating its data structures. On non-POSIX
3592	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3598	systems (Microsoft...) this might be unexpectedly low, but is still at
3593	is still at least 31 bits everywhere, which is enough for hundreds of	3599	least 31 bits everywhere, which is enough for hundreds of millions of
3594	millions of watchers.	3600	watchers.
3595		3601
3596	=item C<double> must hold a time value in seconds with enough accuracy	3602	=item C<double> must hold a time value in seconds with enough accuracy
3597		3603
3598	The type C<double> is used to represent timestamps. It is required to	3604	The type C<double> is used to represent timestamps. It is required to
3599	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3605	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3603	=back	3609	=back
3604		3610
3605	If you know of other additional requirements drop me a note.	3611	If you know of other additional requirements drop me a note.
3606		3612
3607		3613
3608	=head1 COMPILER WARNINGS	3614	=head1 ALGORITHMIC COMPLEXITIES
3609		3615
3610	Depending on your compiler and compiler settings, you might get no or a	3616	In this section the complexities of (many of) the algorithms used inside
3611	lot of warnings when compiling libev code. Some people are apparently	3617	libev will be documented. For complexity discussions about backends see
3612	scared by this.	3618	the documentation for C<ev_default_init>.
3613		3619
3614	However, these are unavoidable for many reasons. For one, each compiler	3620	All of the following are about amortised time: If an array needs to be
3615	has different warnings, and each user has different tastes regarding	3621	extended, libev needs to realloc and move the whole array, but this
3616	warning options. "Warn-free" code therefore cannot be a goal except when	3622	happens asymptotically rarer with higher number of elements, so O(1) might
3617	targeting a specific compiler and compiler-version.	3623	mean that libev does a lengthy realloc operation in rare cases, but on
		3624	average it is much faster and asymptotically approaches constant time.
3618		3625
3619	Another reason is that some compiler warnings require elaborate	3626	=over 4
3620	workarounds, or other changes to the code that make it less clear and less
3621	maintainable.
3622		3627
3623	And of course, some compiler warnings are just plain stupid, or simply	3628	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3624	wrong (because they don't actually warn about the condition their message
3625	seems to warn about).
3626		3629
3627	While libev is written to generate as few warnings as possible,	3630	This means that, when you have a watcher that triggers in one hour and
3628	"warn-free" code is not a goal, and it is recommended not to build libev	3631	there are 100 watchers that would trigger before that, then inserting will
3629	with any compiler warnings enabled unless you are prepared to cope with	3632	have to skip roughly seven (C<ld 100>) of these watchers.
3630	them (e.g. by ignoring them). Remember that warnings are just that:
3631	warnings, not errors, or proof of bugs.
3632		3633
		3634	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3633		3635
3634	=head1 VALGRIND	3636	That means that changing a timer costs less than removing/adding them,
		3637	as only the relative motion in the event queue has to be paid for.
3635		3638
3636	Valgrind has a special section here because it is a popular tool that is	3639	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3637	highly useful, but valgrind reports are very hard to interpret.
3638		3640
3639	If you think you found a bug (memory leak, uninitialised data access etc.)	3641	These just add the watcher into an array or at the head of a list.
3640	in libev, then check twice: If valgrind reports something like:
3641		3642
3642	==2274== definitely lost: 0 bytes in 0 blocks.	3643	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3643	==2274== possibly lost: 0 bytes in 0 blocks.
3644	==2274== still reachable: 256 bytes in 1 blocks.
3645		3644
3646	Then there is no memory leak. Similarly, under some circumstances,	3645	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3647	valgrind might report kernel bugs as if it were a bug in libev, or it
3648	might be confused (it is a very good tool, but only a tool).
3649		3646
3650	If you are unsure about something, feel free to contact the mailing list	3647	These watchers are stored in lists, so they need to be walked to find the
3651	with the full valgrind report and an explanation on why you think this is	3648	correct watcher to remove. The lists are usually short (you don't usually
3652	a bug in libev. However, don't be annoyed when you get a brisk "this is	3649	have many watchers waiting for the same fd or signal: one is typical, two
3653	no bug" answer and take the chance of learning how to interpret valgrind	3650	is rare).
3654	properly.
3655		3651
3656	If you need, for some reason, empty reports from valgrind for your project	3652	=item Finding the next timer in each loop iteration: O(1)
3657	I suggest using suppression lists.	3653
		3654	By virtue of using a binary or 4-heap, the next timer is always found at a
		3655	fixed position in the storage array.
		3656
		3657	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3658
		3659	A change means an I/O watcher gets started or stopped, which requires
		3660	libev to recalculate its status (and possibly tell the kernel, depending
		3661	on backend and whether C<ev_io_set> was used).
		3662
		3663	=item Activating one watcher (putting it into the pending state): O(1)
		3664
		3665	=item Priority handling: O(number_of_priorities)
		3666
		3667	Priorities are implemented by allocating some space for each
		3668	priority. When doing priority-based operations, libev usually has to
		3669	linearly search all the priorities, but starting/stopping and activating
		3670	watchers becomes O(1) with respect to priority handling.
		3671
		3672	=item Sending an ev_async: O(1)
		3673
		3674	=item Processing ev_async_send: O(number_of_async_watchers)
		3675
		3676	=item Processing signals: O(max_signal_number)
		3677
		3678	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3679	calls in the current loop iteration. Checking for async and signal events
		3680	involves iterating over all running async watchers or all signal numbers.
		3681
		3682	=back
3658		3683
3659		3684
3660	=head1 AUTHOR	3685	=head1 AUTHOR
3661		3686
3662	Marc Lehmann <libev@schmorp.de>.	3687	Marc Lehmann <libev@schmorp.de>.

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Comparing libev/ev.pod (file contents): Revision 1.187 by root, Mon Sep 29 03:31:14 2008 UTC vs. Revision 1.197 by root, Tue Oct 21 20:52:30 2008 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.187 by root, Mon Sep 29 03:31:14 2008 UTC vs.
Revision 1.197 by root, Tue Oct 21 20:52:30 2008 UTC