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

Comparing libev/ev.pod (file contents):
Revision 1.184 by root, Tue Sep 23 09:11:14 2008 UTC vs.
Revision 1.194 by root, Mon Oct 20 16:08:36 2008 UTC

…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	215	recommended ones.
216		216
217	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
218		218
219	=item ev_set_allocator (void (cb)(void *ptr, long size))	219	=item ev_set_allocator (void (cb)(void *ptr, long size)) [NOT REENTRANT]
220		220
221	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	223	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	224	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	250	}
251		251
252	...	252	...
253	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
254		254
255	=item ev_set_syserr_cb (void (cb)(const char msg));	255	=item ev_set_syserr_cb (void (cb)(const char msg)); [NOT REENTRANT]
256		256
257	Set the callback function to call on a retryable system call error (such	257	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	260	callback is set, then libev will expect it to remedy the situation, no
…		…
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
…		…
1625		1627
1626	=back	1628	=back
1627		1629
1628	=head3 Examples	1630	=head3 Examples
1629		1631
1630	Example: Try to exit cleanly on SIGINT and SIGTERM.	1632	Example: Try to exit cleanly on SIGINT.
1631		1633
1632	static void	1634	static void
1633	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1635	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
1634	{	1636	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	1637	ev_unloop (loop, EVUNLOOP_ALL);
1636	}	1638	}
1637		1639
1638	struct ev_signal signal_watcher;	1640	struct ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1641	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &sigint_cb);	1642	ev_signal_start (loop, &signal_watcher);
1641		1643
1642		1644
1643	=head2 C<ev_child> - watch out for process status changes	1645	=head2 C<ev_child> - watch out for process status changes
1644		1646
1645	Child watchers trigger when your process receives a SIGCHLD in response to	1647	Child watchers trigger when your process receives a SIGCHLD in response to
…		…
2242	So when you want to use this feature you will always have to be prepared	2244	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	2245	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	2246	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.	2247	create it, and if that fails, use the normal loop for everything.
2246		2248
		2249	=head3 C<ev_embed> and fork
		2250
		2251	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2252	automatically be applied to the embedded loop as well, so no special
		2253	fork handling is required in that case. When the watcher is not running,
		2254	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2255	as applicable.
		2256
2247	=head3 Watcher-Specific Functions and Data Members	2257	=head3 Watcher-Specific Functions and Data Members
2248		2258
2249	=over 4	2259	=over 4
2250		2260
2251	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)	2261	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
…		…
2376	=over 4	2386	=over 4
2377		2387
2378	=item queueing from a signal handler context	2388	=item queueing from a signal handler context
2379		2389
2380	To implement race-free queueing, you simply add to the queue in the signal	2390	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	2391	handler but you block the signal handler in the watcher callback. Here is
2382	some fictitious SIGUSR1 handler:	2392	an example that does that for some fictitious SIGUSR1 handler:
2383		2393
2384	static ev_async mysig;	2394	static ev_async mysig;
2385		2395
2386	static void	2396	static void
2387	sigusr1_handler (void)	2397	sigusr1_handler (void)
…		…
2494	=over 4	2504	=over 4
2495		2505
2496	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2506	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2497		2507
2498	This function combines a simple timer and an I/O watcher, calls your	2508	This function combines a simple timer and an I/O watcher, calls your
2499	callback on whichever event happens first and automatically stop both	2509	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	2510	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	2511	or timeout without having to allocate/configure/start/stop/free one or
2502	more watchers yourself.	2512	more watchers yourself.
2503		2513
2504	If C<fd> is less than 0, then no I/O watcher will be started and events	2514	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	2515	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2506	C<events> set will be created and started.	2516	the given C<fd> and C<events> set will be created and started.
2507		2517
2508	If C<timeout> is less than 0, then no timeout watcher will be	2518	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	2519	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	2520	repeat = 0) will be started. C<0> is a valid timeout.
2511	dubious value.
2512		2521
2513	The callback has the type C<void (cb)(int revents, void arg)> and gets	2522	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	2523	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>	2524	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2516	value passed to C<ev_once>:	2525	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2526	a timeout and an io event at the same time - you probably should give io
		2527	events precedence.
		2528
		2529	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2517		2530
2518	static void stdin_ready (int revents, void *arg)	2531	static void stdin_ready (int revents, void *arg)
2519	{	2532	{
		2533	if (revents & EV_READ)
		2534	/* stdin might have data for us, joy! */;
2520	if (revents & EV_TIMEOUT)	2535	else if (revents & EV_TIMEOUT)
2521	/* doh, nothing entered */;	2536	/* doh, nothing entered */;
2522	else if (revents & EV_READ)
2523	/* stdin might have data for us, joy! */;
2524	}	2537	}
2525		2538
2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2539	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2527		2540
2528	=item ev_feed_event (ev_loop , watcher , int revents)	2541	=item ev_feed_event (ev_loop , watcher , int revents)
…		…
3241	definition and a statement, respectively. See the F<ev.h> header file for	3254	definition and a statement, respectively. See the F<ev.h> header file for
3242	their default definitions. One possible use for overriding these is to	3255	their default definitions. One possible use for overriding these is to
3243	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3256	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3244	method calls instead of plain function calls in C++.	3257	method calls instead of plain function calls in C++.
3245		3258
		3259	=back
		3260
3246	=head2 EXPORTED API SYMBOLS	3261	=head2 EXPORTED API SYMBOLS
3247		3262
3248	If you need to re-export the API (e.g. via a DLL) and you need a list of	3263	If you need to re-export the API (e.g. via a DLL) and you need a list of
3249	exported symbols, you can use the provided F<Symbol.*> files which list	3264	exported symbols, you can use the provided F<Symbol.*> files which list
3250	all public symbols, one per line:	3265	all public symbols, one per line:
…		…
3296	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3311	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3297		3312
3298	#include "ev_cpp.h"	3313	#include "ev_cpp.h"
3299	#include "ev.c"	3314	#include "ev.c"
3300		3315
		3316	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3301		3317
3302	=head1 THREADS AND COROUTINES	3318	=head2 THREADS AND COROUTINES
3303		3319
3304	=head2 THREADS	3320	=head3 THREADS
3305		3321
3306	Libev itself is thread-safe (unless the opposite is specifically	3322	All libev functions are reentrant and thread-safe unless explicitly
3307	documented for a function), but it uses no locking itself. This means that	3323	documented otherwise, but libev implements no locking itself. This means
3308	you can use as many loops as you want in parallel, as long as only one	3324	that you can use as many loops as you want in parallel, as long as there
3309	thread ever calls into one libev function with the same loop parameter:	3325	are no concurrent calls into any libev function with the same loop
		3326	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3310	libev guarantees that different event loops share no data structures that	3327	of course): libev guarantees that different event loops share no data
3311	need locking.	3328	structures that need any locking.
3312		3329
3313	Or to put it differently: calls with different loop parameters can be done	3330	Or to put it differently: calls with different loop parameters can be done
3314	concurrently from multiple threads, calls with the same loop parameter	3331	concurrently from multiple threads, calls with the same loop parameter
3315	must be done serially (but can be done from different threads, as long as	3332	must be done serially (but can be done from different threads, as long as
3316	only one thread ever is inside a call at any point in time, e.g. by using	3333	only one thread ever is inside a call at any point in time, e.g. by using
3317	a mutex per loop).	3334	a mutex per loop).
3318		3335
3319	Specifically to support threads (and signal handlers), libev implements	3336	Specifically to support threads (and signal handlers), libev implements
3320	so-called C<ev_async> watchers, which allow some limited form of	3337	so-called C<ev_async> watchers, which allow some limited form of
3321	concurrency on the same event loop.	3338	concurrency on the same event loop, namely waking it up "from the
		3339	outside".
3322		3340
3323	If you want to know which design (one loop, locking, or multiple loops	3341	If you want to know which design (one loop, locking, or multiple loops
3324	without or something else still) is best for your problem, then I cannot	3342	without or something else still) is best for your problem, then I cannot
3325	help you. I can give some generic advice however:	3343	help you, but here is some generic advice:
3326		3344
3327	=over 4	3345	=over 4
3328		3346
3329	=item * most applications have a main thread: use the default libev loop	3347	=item * most applications have a main thread: use the default libev loop
3330	in that thread, or create a separate thread running only the default loop.	3348	in that thread, or create a separate thread running only the default loop.
…		…
3354	default loop and triggering an C<ev_async> watcher from the default loop	3372	default loop and triggering an C<ev_async> watcher from the default loop
3355	watcher callback into the event loop interested in the signal.	3373	watcher callback into the event loop interested in the signal.
3356		3374
3357	=back	3375	=back
3358		3376
3359	=head2 COROUTINES	3377	=head3 COROUTINES
3360		3378
3361	Libev is much more accommodating to coroutines ("cooperative threads"):	3379	Libev is very accommodating to coroutines ("cooperative threads"):
3362	libev fully supports nesting calls to it's functions from different	3380	libev fully supports nesting calls to its functions from different
3363	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3381	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3364	different coroutines and switch freely between both coroutines running the	3382	different coroutines, and switch freely between both coroutines running the
3365	loop, as long as you don't confuse yourself). The only exception is that	3383	loop, as long as you don't confuse yourself). The only exception is that
3366	you must not do this from C<ev_periodic> reschedule callbacks.	3384	you must not do this from C<ev_periodic> reschedule callbacks.
3367		3385
3368	Care has been taken to ensure that libev does not keep local state inside	3386	Care has been taken to ensure that libev does not keep local state inside
3369	C<ev_loop>, and other calls do not usually allow coroutine switches.	3387	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3388	they do not clal any callbacks.
3370		3389
		3390	=head2 COMPILER WARNINGS
3371		3391
3372	=head1 COMPLEXITIES	3392	Depending on your compiler and compiler settings, you might get no or a
		3393	lot of warnings when compiling libev code. Some people are apparently
		3394	scared by this.
3373		3395
3374	In this section the complexities of (many of) the algorithms used inside	3396	However, these are unavoidable for many reasons. For one, each compiler
3375	libev will be explained. For complexity discussions about backends see the	3397	has different warnings, and each user has different tastes regarding
3376	documentation for C<ev_default_init>.	3398	warning options. "Warn-free" code therefore cannot be a goal except when
		3399	targeting a specific compiler and compiler-version.
3377		3400
3378	All of the following are about amortised time: If an array needs to be	3401	Another reason is that some compiler warnings require elaborate
3379	extended, libev needs to realloc and move the whole array, but this	3402	workarounds, or other changes to the code that make it less clear and less
3380	happens asymptotically never with higher number of elements, so O(1) might	3403	maintainable.
3381	mean it might do a lengthy realloc operation in rare cases, but on average
3382	it is much faster and asymptotically approaches constant time.
3383		3404
3384	=over 4	3405	And of course, some compiler warnings are just plain stupid, or simply
		3406	wrong (because they don't actually warn about the condition their message
		3407	seems to warn about). For example, certain older gcc versions had some
		3408	warnings that resulted an extreme number of false positives. These have
		3409	been fixed, but some people still insist on making code warn-free with
		3410	such buggy versions.
3385		3411
3386	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3412	While libev is written to generate as few warnings as possible,
		3413	"warn-free" code is not a goal, and it is recommended not to build libev
		3414	with any compiler warnings enabled unless you are prepared to cope with
		3415	them (e.g. by ignoring them). Remember that warnings are just that:
		3416	warnings, not errors, or proof of bugs.
3387		3417
3388	This means that, when you have a watcher that triggers in one hour and
3389	there are 100 watchers that would trigger before that then inserting will
3390	have to skip roughly seven (C<ld 100>) of these watchers.
3391		3418
3392	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3419	=head2 VALGRIND
3393		3420
3394	That means that changing a timer costs less than removing/adding them	3421	Valgrind has a special section here because it is a popular tool that is
3395	as only the relative motion in the event queue has to be paid for.	3422	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3396		3423
3397	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3424	If you think you found a bug (memory leak, uninitialised data access etc.)
		3425	in libev, then check twice: If valgrind reports something like:
3398		3426
3399	These just add the watcher into an array or at the head of a list.	3427	==2274== definitely lost: 0 bytes in 0 blocks.
		3428	==2274== possibly lost: 0 bytes in 0 blocks.
		3429	==2274== still reachable: 256 bytes in 1 blocks.
3400		3430
3401	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3431	Then there is no memory leak, just as memory accounted to global variables
		3432	is not a memleak - the memory is still being refernced, and didn't leak.
3402		3433
3403	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3434	Similarly, under some circumstances, valgrind might report kernel bugs
		3435	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3436	although an acceptable workaround has been found here), or it might be
		3437	confused.
3404		3438
3405	These watchers are stored in lists then need to be walked to find the	3439	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3406	correct watcher to remove. The lists are usually short (you don't usually	3440	make it into some kind of religion.
3407	have many watchers waiting for the same fd or signal).
3408		3441
3409	=item Finding the next timer in each loop iteration: O(1)	3442	If you are unsure about something, feel free to contact the mailing list
		3443	with the full valgrind report and an explanation on why you think this
		3444	is a bug in libev (best check the archives, too :). However, don't be
		3445	annoyed when you get a brisk "this is no bug" answer and take the chance
		3446	of learning how to interpret valgrind properly.
3410		3447
3411	By virtue of using a binary or 4-heap, the next timer is always found at a	3448	If you need, for some reason, empty reports from valgrind for your project
3412	fixed position in the storage array.	3449	I suggest using suppression lists.
3413		3450
3414	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3415		3451
3416	A change means an I/O watcher gets started or stopped, which requires	3452	=head1 PORTABILITY NOTES
3417	libev to recalculate its status (and possibly tell the kernel, depending
3418	on backend and whether C<ev_io_set> was used).
3419		3453
3420	=item Activating one watcher (putting it into the pending state): O(1)
3421
3422	=item Priority handling: O(number_of_priorities)
3423
3424	Priorities are implemented by allocating some space for each
3425	priority. When doing priority-based operations, libev usually has to
3426	linearly search all the priorities, but starting/stopping and activating
3427	watchers becomes O(1) with respect to priority handling.
3428
3429	=item Sending an ev_async: O(1)
3430
3431	=item Processing ev_async_send: O(number_of_async_watchers)
3432
3433	=item Processing signals: O(max_signal_number)
3434
3435	Sending involves a system call I<iff> there were no other C<ev_async_send>
3436	calls in the current loop iteration. Checking for async and signal events
3437	involves iterating over all running async watchers or all signal numbers.
3438
3439	=back
3440
3441
3442	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3454	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3443		3455
3444	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3456	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3445	requires, and its I/O model is fundamentally incompatible with the POSIX	3457	requires, and its I/O model is fundamentally incompatible with the POSIX
3446	model. Libev still offers limited functionality on this platform in	3458	model. Libev still offers limited functionality on this platform in
3447	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3459	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3534	wrap all I/O functions and provide your own fd management, but the cost of	3546	wrap all I/O functions and provide your own fd management, but the cost of
3535	calling select (O(n²)) will likely make this unworkable.	3547	calling select (O(n²)) will likely make this unworkable.
3536		3548
3537	=back	3549	=back
3538		3550
3539
3540	=head1 PORTABILITY REQUIREMENTS	3551	=head2 PORTABILITY REQUIREMENTS
3541		3552
3542	In addition to a working ISO-C implementation, libev relies on a few	3553	In addition to a working ISO-C implementation and of course the
3543	additional extensions:	3554	backend-specific APIs, libev relies on a few additional extensions:
3544		3555
3545	=over 4	3556	=over 4
3546		3557
3547	=item C<void ()(ev_watcher_type , int revents)> must have compatible	3558	=item C<void ()(ev_watcher_type , int revents)> must have compatible
3548	calling conventions regardless of C<ev_watcher_type *>.	3559	calling conventions regardless of C<ev_watcher_type *>.
…		…
3573	except the initial one, and run the default loop in the initial thread as	3584	except the initial one, and run the default loop in the initial thread as
3574	well.	3585	well.
3575		3586
3576	=item C<long> must be large enough for common memory allocation sizes	3587	=item C<long> must be large enough for common memory allocation sizes
3577		3588
3578	To improve portability and simplify using libev, libev uses C<long>	3589	To improve portability and simplify its API, libev uses C<long> internally
3579	internally instead of C<size_t> when allocating its data structures. On	3590	instead of C<size_t> when allocating its data structures. On non-POSIX
3580	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3591	systems (Microsoft...) this might be unexpectedly low, but is still at
3581	is still at least 31 bits everywhere, which is enough for hundreds of	3592	least 31 bits everywhere, which is enough for hundreds of millions of
3582	millions of watchers.	3593	watchers.
3583		3594
3584	=item C<double> must hold a time value in seconds with enough accuracy	3595	=item C<double> must hold a time value in seconds with enough accuracy
3585		3596
3586	The type C<double> is used to represent timestamps. It is required to	3597	The type C<double> is used to represent timestamps. It is required to
3587	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3598	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3591	=back	3602	=back
3592		3603
3593	If you know of other additional requirements drop me a note.	3604	If you know of other additional requirements drop me a note.
3594		3605
3595		3606
3596	=head1 COMPILER WARNINGS	3607	=head1 ALGORITHMIC COMPLEXITIES
3597		3608
3598	Depending on your compiler and compiler settings, you might get no or a	3609	In this section the complexities of (many of) the algorithms used inside
3599	lot of warnings when compiling libev code. Some people are apparently	3610	libev will be documented. For complexity discussions about backends see
3600	scared by this.	3611	the documentation for C<ev_default_init>.
3601		3612
3602	However, these are unavoidable for many reasons. For one, each compiler	3613	All of the following are about amortised time: If an array needs to be
3603	has different warnings, and each user has different tastes regarding	3614	extended, libev needs to realloc and move the whole array, but this
3604	warning options. "Warn-free" code therefore cannot be a goal except when	3615	happens asymptotically rarer with higher number of elements, so O(1) might
3605	targeting a specific compiler and compiler-version.	3616	mean that libev does a lengthy realloc operation in rare cases, but on
		3617	average it is much faster and asymptotically approaches constant time.
3606		3618
3607	Another reason is that some compiler warnings require elaborate	3619	=over 4
3608	workarounds, or other changes to the code that make it less clear and less
3609	maintainable.
3610		3620
3611	And of course, some compiler warnings are just plain stupid, or simply	3621	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3612	wrong (because they don't actually warn about the condition their message
3613	seems to warn about).
3614		3622
3615	While libev is written to generate as few warnings as possible,	3623	This means that, when you have a watcher that triggers in one hour and
3616	"warn-free" code is not a goal, and it is recommended not to build libev	3624	there are 100 watchers that would trigger before that, then inserting will
3617	with any compiler warnings enabled unless you are prepared to cope with	3625	have to skip roughly seven (C<ld 100>) of these watchers.
3618	them (e.g. by ignoring them). Remember that warnings are just that:
3619	warnings, not errors, or proof of bugs.
3620		3626
		3627	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3621		3628
3622	=head1 VALGRIND	3629	That means that changing a timer costs less than removing/adding them,
		3630	as only the relative motion in the event queue has to be paid for.
3623		3631
3624	Valgrind has a special section here because it is a popular tool that is	3632	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3625	highly useful, but valgrind reports are very hard to interpret.
3626		3633
3627	If you think you found a bug (memory leak, uninitialised data access etc.)	3634	These just add the watcher into an array or at the head of a list.
3628	in libev, then check twice: If valgrind reports something like:
3629		3635
3630	==2274== definitely lost: 0 bytes in 0 blocks.	3636	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3631	==2274== possibly lost: 0 bytes in 0 blocks.
3632	==2274== still reachable: 256 bytes in 1 blocks.
3633		3637
3634	Then there is no memory leak. Similarly, under some circumstances,	3638	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3635	valgrind might report kernel bugs as if it were a bug in libev, or it
3636	might be confused (it is a very good tool, but only a tool).
3637		3639
3638	If you are unsure about something, feel free to contact the mailing list	3640	These watchers are stored in lists, so they need to be walked to find the
3639	with the full valgrind report and an explanation on why you think this is	3641	correct watcher to remove. The lists are usually short (you don't usually
3640	a bug in libev. However, don't be annoyed when you get a brisk "this is	3642	have many watchers waiting for the same fd or signal: one is typical, two
3641	no bug" answer and take the chance of learning how to interpret valgrind	3643	is rare).
3642	properly.
3643		3644
3644	If you need, for some reason, empty reports from valgrind for your project	3645	=item Finding the next timer in each loop iteration: O(1)
3645	I suggest using suppression lists.	3646
		3647	By virtue of using a binary or 4-heap, the next timer is always found at a
		3648	fixed position in the storage array.
		3649
		3650	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3651
		3652	A change means an I/O watcher gets started or stopped, which requires
		3653	libev to recalculate its status (and possibly tell the kernel, depending
		3654	on backend and whether C<ev_io_set> was used).
		3655
		3656	=item Activating one watcher (putting it into the pending state): O(1)
		3657
		3658	=item Priority handling: O(number_of_priorities)
		3659
		3660	Priorities are implemented by allocating some space for each
		3661	priority. When doing priority-based operations, libev usually has to
		3662	linearly search all the priorities, but starting/stopping and activating
		3663	watchers becomes O(1) with respect to priority handling.
		3664
		3665	=item Sending an ev_async: O(1)
		3666
		3667	=item Processing ev_async_send: O(number_of_async_watchers)
		3668
		3669	=item Processing signals: O(max_signal_number)
		3670
		3671	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3672	calls in the current loop iteration. Checking for async and signal events
		3673	involves iterating over all running async watchers or all signal numbers.
		3674
		3675	=back
3646		3676
3647		3677
3648	=head1 AUTHOR	3678	=head1 AUTHOR
3649		3679
3650	Marc Lehmann <libev@schmorp.de>.	3680	Marc Lehmann <libev@schmorp.de>.

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Comparing libev/ev.pod (file contents): Revision 1.184 by root, Tue Sep 23 09:11:14 2008 UTC vs. Revision 1.194 by root, Mon Oct 20 16:08:36 2008 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.184 by root, Tue Sep 23 09:11:14 2008 UTC vs.
Revision 1.194 by root, Mon Oct 20 16:08:36 2008 UTC