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

Comparing libev/ev.pod (file contents):
Revision 1.186 by root, Wed Sep 24 07:56:14 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,
…		…
2242	So when you want to use this feature you will always have to be prepared	2251	So when you want to use this feature you will always have to be prepared
2243	that you cannot get an embeddable loop. The recommended way to get around	2252	that you cannot get an embeddable loop. The recommended way to get around
2244	this is to have a separate variables for your embeddable loop, try to	2253	this is to have a separate variables for your embeddable loop, try to
2245	create it, and if that fails, use the normal loop for everything.	2254	create it, and if that fails, use the normal loop for everything.
2246		2255
		2256	=head3 C<ev_embed> and fork
		2257
		2258	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2259	automatically be applied to the embedded loop as well, so no special
		2260	fork handling is required in that case. When the watcher is not running,
		2261	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2262	as applicable.
		2263
2247	=head3 Watcher-Specific Functions and Data Members	2264	=head3 Watcher-Specific Functions and Data Members
2248		2265
2249	=over 4	2266	=over 4
2250		2267
2251	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)	2268	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
…		…
2376	=over 4	2393	=over 4
2377		2394
2378	=item queueing from a signal handler context	2395	=item queueing from a signal handler context
2379		2396
2380	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
2381	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
2382	some fictitious SIGUSR1 handler:	2399	an example that does that for some fictitious SIGUSR1 handler:
2383		2400
2384	static ev_async mysig;	2401	static ev_async mysig;
2385		2402
2386	static void	2403	static void
2387	sigusr1_handler (void)	2404	sigusr1_handler (void)
…		…
2494	=over 4	2511	=over 4
2495		2512
2496	=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)
2497		2514
2498	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
2499	callback on whichever event happens first and automatically stop both	2516	callback on whichever event happens first and automatically stops both
2500	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
2501	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
2502	more watchers yourself.	2519	more watchers yourself.
2503		2520
2504	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
2505	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
2506	C<events> set will be created and started.	2523	the given C<fd> and C<events> set will be created and started.
2507		2524
2508	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
2509	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
2510	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.
2511	dubious value.
2512		2528
2513	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
2514	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
2515	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>
2516	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.
2517		2537
2518	static void stdin_ready (int revents, void *arg)	2538	static void stdin_ready (int revents, void *arg)
2519	{	2539	{
		2540	if (revents & EV_READ)
		2541	/* stdin might have data for us, joy! */;
2520	if (revents & EV_TIMEOUT)	2542	else if (revents & EV_TIMEOUT)
2521	/* doh, nothing entered */;	2543	/* doh, nothing entered */;
2522	else if (revents & EV_READ)
2523	/* stdin might have data for us, joy! */;
2524	}	2544	}
2525		2545
2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2546	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2527		2547
2528	=item ev_feed_event (ev_loop , watcher , int revents)	2548	=item ev_feed_event (ev_loop , watcher , int revents)
…		…
3298	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:
3299		3319
3300	#include "ev_cpp.h"	3320	#include "ev_cpp.h"
3301	#include "ev.c"	3321	#include "ev.c"
3302		3322
		3323	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3303		3324
3304	=head1 THREADS AND COROUTINES	3325	=head2 THREADS AND COROUTINES
3305		3326
3306	=head2 THREADS	3327	=head3 THREADS
3307		3328
3308	All libev functions are reentrant and thread-safe unless explicitly	3329	All libev functions are reentrant and thread-safe unless explicitly
3309	documented otherwise, but it uses no locking itself. This means that you	3330	documented otherwise, but libev implements no locking itself. This means
3310	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
3311	concurrent calls into any libev function with the same loop parameter	3332	are no concurrent calls into any libev function with the same loop
3312	(C<ev_default_*> calls have an implicit default loop parameter, of	3333	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3313	course): libev guarantees that different event loops share no data	3334	of course): libev guarantees that different event loops share no data
3314	structures that need any locking.	3335	structures that need any locking.
3315		3336
3316	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
3317	concurrently from multiple threads, calls with the same loop parameter	3338	concurrently from multiple threads, calls with the same loop parameter
3318	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
…		…
3358	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
3359	watcher callback into the event loop interested in the signal.	3380	watcher callback into the event loop interested in the signal.
3360		3381
3361	=back	3382	=back
3362		3383
3363	=head2 COROUTINES	3384	=head3 COROUTINES
3364		3385
3365	Libev is much more accommodating to coroutines ("cooperative threads"):	3386	Libev is very accommodating to coroutines ("cooperative threads"):
3366	libev fully supports nesting calls to it's functions from different	3387	libev fully supports nesting calls to its functions from different
3367	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
3368	different coroutines and switch freely between both coroutines running the	3389	different coroutines, and switch freely between both coroutines running the
3369	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
3370	you must not do this from C<ev_periodic> reschedule callbacks.	3391	you must not do this from C<ev_periodic> reschedule callbacks.
3371		3392
3372	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
3373	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.
3374		3396
		3397	=head2 COMPILER WARNINGS
3375		3398
3376	=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.
3377		3402
3378	In this section the complexities of (many of) the algorithms used inside	3403	However, these are unavoidable for many reasons. For one, each compiler
3379	libev will be explained. For complexity discussions about backends see the	3404	has different warnings, and each user has different tastes regarding
3380	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.
3381		3407
3382	All of the following are about amortised time: If an array needs to be	3408	Another reason is that some compiler warnings require elaborate
3383	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
3384	happens asymptotically never with higher number of elements, so O(1) might	3410	maintainable.
3385	mean it might do a lengthy realloc operation in rare cases, but on average
3386	it is much faster and asymptotically approaches constant time.
3387		3411
3388	=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.
3389		3418
3390	=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.
3391		3424
3392	This means that, when you have a watcher that triggers in one hour and
3393	there are 100 watchers that would trigger before that then inserting will
3394	have to skip roughly seven (C<ld 100>) of these watchers.
3395		3425
3396	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3426	=head2 VALGRIND
3397		3427
3398	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
3399	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.
3400		3430
3401	=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:
3402		3433
3403	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.
3404		3437
3405	=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.
3406		3440
3407	=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.
3408		3445
3409	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
3410	correct watcher to remove. The lists are usually short (you don't usually	3447	make it into some kind of religion.
3411	have many watchers waiting for the same fd or signal).
3412		3448
3413	=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.
3414		3454
3415	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
3416	fixed position in the storage array.	3456	I suggest using suppression lists.
3417		3457
3418	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3419		3458
3420	A change means an I/O watcher gets started or stopped, which requires	3459	=head1 PORTABILITY NOTES
3421	libev to recalculate its status (and possibly tell the kernel, depending
3422	on backend and whether C<ev_io_set> was used).
3423		3460
3424	=item Activating one watcher (putting it into the pending state): O(1)
3425
3426	=item Priority handling: O(number_of_priorities)
3427
3428	Priorities are implemented by allocating some space for each
3429	priority. When doing priority-based operations, libev usually has to
3430	linearly search all the priorities, but starting/stopping and activating
3431	watchers becomes O(1) with respect to priority handling.
3432
3433	=item Sending an ev_async: O(1)
3434
3435	=item Processing ev_async_send: O(number_of_async_watchers)
3436
3437	=item Processing signals: O(max_signal_number)
3438
3439	Sending involves a system call I<iff> there were no other C<ev_async_send>
3440	calls in the current loop iteration. Checking for async and signal events
3441	involves iterating over all running async watchers or all signal numbers.
3442
3443	=back
3444
3445
3446	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3461	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3447		3462
3448	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
3449	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
3450	model. Libev still offers limited functionality on this platform in	3465	model. Libev still offers limited functionality on this platform in
3451	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
…		…
3538	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
3539	calling select (O(n²)) will likely make this unworkable.	3554	calling select (O(n²)) will likely make this unworkable.
3540		3555
3541	=back	3556	=back
3542		3557
3543
3544	=head1 PORTABILITY REQUIREMENTS	3558	=head2 PORTABILITY REQUIREMENTS
3545		3559
3546	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
3547	additional extensions:	3561	backend-specific APIs, libev relies on a few additional extensions:
3548		3562
3549	=over 4	3563	=over 4
3550		3564
3551	=item C<void ()(ev_watcher_type , int revents)> must have compatible	3565	=item C<void ()(ev_watcher_type , int revents)> must have compatible
3552	calling conventions regardless of C<ev_watcher_type *>.	3566	calling conventions regardless of C<ev_watcher_type *>.
…		…
3577	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
3578	well.	3592	well.
3579		3593
3580	=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
3581		3595
3582	To improve portability and simplify using libev, libev uses C<long>	3596	To improve portability and simplify its API, libev uses C<long> internally
3583	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
3584	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3598	systems (Microsoft...) this might be unexpectedly low, but is still at
3585	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
3586	millions of watchers.	3600	watchers.
3587		3601
3588	=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
3589		3603
3590	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
3591	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
…		…
3595	=back	3609	=back
3596		3610
3597	If you know of other additional requirements drop me a note.	3611	If you know of other additional requirements drop me a note.
3598		3612
3599		3613
3600	=head1 COMPILER WARNINGS	3614	=head1 ALGORITHMIC COMPLEXITIES
3601		3615
3602	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
3603	lot of warnings when compiling libev code. Some people are apparently	3617	libev will be documented. For complexity discussions about backends see
3604	scared by this.	3618	the documentation for C<ev_default_init>.
3605		3619
3606	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
3607	has different warnings, and each user has different tastes regarding	3621	extended, libev needs to realloc and move the whole array, but this
3608	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
3609	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.
3610		3625
3611	Another reason is that some compiler warnings require elaborate	3626	=over 4
3612	workarounds, or other changes to the code that make it less clear and less
3613	maintainable.
3614		3627
3615	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)
3616	wrong (because they don't actually warn about the condition their message
3617	seems to warn about).
3618		3629
3619	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
3620	"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
3621	with any compiler warnings enabled unless you are prepared to cope with	3632	have to skip roughly seven (C<ld 100>) of these watchers.
3622	them (e.g. by ignoring them). Remember that warnings are just that:
3623	warnings, not errors, or proof of bugs.
3624		3633
		3634	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3625		3635
3626	=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.
3627		3638
3628	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)
3629	highly useful, but valgrind reports are very hard to interpret.
3630		3640
3631	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.
3632	in libev, then check twice: If valgrind reports something like:
3633		3642
3634	==2274== definitely lost: 0 bytes in 0 blocks.	3643	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3635	==2274== possibly lost: 0 bytes in 0 blocks.
3636	==2274== still reachable: 256 bytes in 1 blocks.
3637		3644
3638	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))
3639	valgrind might report kernel bugs as if it were a bug in libev, or it
3640	might be confused (it is a very good tool, but only a tool).
3641		3646
3642	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
3643	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
3644	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
3645	no bug" answer and take the chance of learning how to interpret valgrind	3650	is rare).
3646	properly.
3647		3651
3648	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)
3649	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
3650		3683
3651		3684
3652	=head1 AUTHOR	3685	=head1 AUTHOR
3653		3686
3654	Marc Lehmann <libev@schmorp.de>.	3687	Marc Lehmann <libev@schmorp.de>.

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing libev/ev.pod (file contents): Revision 1.186 by root, Wed Sep 24 07:56:14 2008 UTC vs. Revision 1.197 by root, Tue Oct 21 20:52:30 2008 UTC

Diff Legend

Comparing libev/ev.pod (file contents):
Revision 1.186 by root, Wed Sep 24 07:56:14 2008 UTC vs.
Revision 1.197 by root, Tue Oct 21 20:52:30 2008 UTC