[ViewVC] Diff of: cvs/libeio/eio.pod

Comparing libeio/eio.pod (file contents):
Revision 1.15 by root, Tue Jul 5 16:57:41 2011 UTC vs.
Revision 1.27 by root, Sun Jul 24 03:32:54 2011 UTC

…		…
45	Unlike the name component C<stamp> might indicate, it is also used for	45	Unlike the name component C<stamp> might indicate, it is also used for
46	time differences throughout libeio.	46	time differences throughout libeio.
47		47
48	=head2 FORK SUPPORT	48	=head2 FORK SUPPORT
49		49
50	Calling C<fork ()> is fully supported by this module. It is implemented in these steps:	50	Usage of pthreads in a program changes the semantics of fork
		51	considerably. Specifically, only async-safe functions can be called after
		52	fork. Libeio uses pthreads, so this applies, and makes using fork hard for
		53	anything but relatively fork + exec uses.
51		54
52	1. wait till all requests in "execute" state have been handled	55	This library only works in the process that initialised it: Forking is
53	(basically requests that are already handed over to the kernel).	56	fully supported, but using libeio in any other process than the one that
54	2. fork	57	called C<eio_init> is not.
55	3. in the parent, continue business as usual, done
56	4. in the child, destroy all ready and pending requests and free the
57	memory used by the worker threads. This gives you a fully empty
58	libeio queue.
59		58
60	Note, however, since libeio does use threads, thr above guarantee doesn't	59	You might get around by not I<using> libeio before (or after) forking in
61	cover your libc, for example, malloc and other libc functions are not	60	the parent, and using it in the child afterwards. You could also try to
62	fork-safe, so there is very little you can do after a fork, and in fatc,	61	call the L<eio_init> function again in the child, which will brutally
63	the above might crash, and thus change.	62	reinitialise all data structures, which isn't POSIX conformant, but
		63	typically works.
		64
		65	Otherwise, the only recommendation you should follow is: treat fork code
		66	the same way you treat signal handlers, and only ever call C<eio_init> in
		67	the process that uses it, and only once ever.
64		68
65	=head1 INITIALISATION/INTEGRATION	69	=head1 INITIALISATION/INTEGRATION
66		70
67	Before you can call any eio functions you first have to initialise the	71	Before you can call any eio functions you first have to initialise the
68	library. The library integrates into any event loop, but can also be used	72	library. The library integrates into any event loop, but can also be used
…		…
77	This function initialises the library. On success it returns C<0>, on	81	This function initialises the library. On success it returns C<0>, on
78	failure it returns C<-1> and sets C<errno> appropriately.	82	failure it returns C<-1> and sets C<errno> appropriately.
79		83
80	It accepts two function pointers specifying callbacks as argument, both of	84	It accepts two function pointers specifying callbacks as argument, both of
81	which can be C<0>, in which case the callback isn't called.	85	which can be C<0>, in which case the callback isn't called.
		86
		87	There is currently no way to change these callbacks later, or to
		88	"uninitialise" the library again.
82		89
83	=item want_poll callback	90	=item want_poll callback
84		91
85	The C<want_poll> callback is invoked whenever libeio wants attention (i.e.	92	The C<want_poll> callback is invoked whenever libeio wants attention (i.e.
86	it wants to be polled by calling C<eio_poll>). It is "edge-triggered",	93	it wants to be polled by calling C<eio_poll>). It is "edge-triggered",
…		…
130		137
131	If C<eio_poll ()> is configured to not handle all results in one go	138	If C<eio_poll ()> is configured to not handle all results in one go
132	(i.e. it returns C<-1>) then you should start an idle watcher that calls	139	(i.e. it returns C<-1>) then you should start an idle watcher that calls
133	C<eio_poll> until it returns something C<!= -1>.	140	C<eio_poll> until it returns something C<!= -1>.
134		141
135	A full-featured wrapper would look as follows (if C<eio_poll> is handling	142	A full-featured connector between libeio and libev would look as follows
136	all requests, it can of course be simplified a lot by removing the idle	143	(if C<eio_poll> is handling all requests, it can of course be simplified a
137	watcher logic):	144	lot by removing the idle watcher logic):
138		145
139	static struct ev_loop *loop;	146	static struct ev_loop *loop;
140	static ev_idle repeat_watcher;	147	static ev_idle repeat_watcher;
141	static ev_async ready_watcher;	148	static ev_async ready_watcher;
142		149
143	/* idle watcher callback, only used when eio_poll */	150	/* idle watcher callback, only used when eio_poll */
144	/* didn't handle all results in one call */	151	/* didn't handle all results in one call */
145	static void	152	static void
146	repeat (EV_P_ ev_idle *w, int revents)	153	repeat (EV_P_ ev_idle *w, int revents)
147	{	154	{
148	if (eio_poll () != -1)	155	if (eio_poll () != -1)
149	ev_idle_stop (EV_A_ w);	156	ev_idle_stop (EV_A_ w);
150	}	157	}
151		158
152	/* eio has some results, process them */	159	/* eio has some results, process them */
153	static void	160	static void
154	ready (EV_P_ ev_async *w, int revents)	161	ready (EV_P_ ev_async *w, int revents)
155	{	162	{
156	if (eio_poll () == -1)	163	if (eio_poll () == -1)
157	ev_idle_start (EV_A_ &repeat_watcher);	164	ev_idle_start (EV_A_ &repeat_watcher);
158	}	165	}
159		166
160	/* wake up the event loop */	167	/* wake up the event loop */
161	static void	168	static void
162	want_poll (void)	169	want_poll (void)
163	{	170	{
164	ev_async_send (loop, &ready_watcher)	171	ev_async_send (loop, &ready_watcher)
165	}	172	}
166		173
167	void	174	void
168	my_init_eio ()	175	my_init_eio ()
169	{	176	{
170	loop = EV_DEFAULT;	177	loop = EV_DEFAULT;
171		178
172	ev_idle_init (&repeat_watcher, repeat);	179	ev_idle_init (&repeat_watcher, repeat);
173	ev_async_init (&ready_watcher, ready);	180	ev_async_init (&ready_watcher, ready);
174	ev_async_start (loop &watcher);	181	ev_async_start (loop &watcher);
175		182
176	eio_init (want_poll, 0);	183	eio_init (want_poll, 0);
177	}	184	}
178		185
179	For most other event loops, you would typically use a pipe - the event	186	For most other event loops, you would typically use a pipe - the event
180	loop should be told to wait for read readiness on the read end. In	187	loop should be told to wait for read readiness on the read end. In
181	C<want_poll> you would write a single byte, in C<done_poll> you would try	188	C<want_poll> you would write a single byte, in C<done_poll> you would try
182	to read that byte, and in the callback for the read end, you would call	189	to read that byte, and in the callback for the read end, you would call
183	C<eio_poll>. The race is avoided here because the event loop should invoke	190	C<eio_poll>.
184	your callback again and again until the byte has been read (as the pipe	191
185	read callback does not read it, only C<done_poll>).	192	You don't have to take special care in the case C<eio_poll> doesn't handle
		193	all requests, as the done callback will not be invoked, so the event loop
		194	will still signal readiness for the pipe until I<all> results have been
		195	processed.
186		196
187		197
188	=head1 HIGH LEVEL REQUEST API	198	=head1 HIGH LEVEL REQUEST API
189		199
190	Libeio has both a high-level API, which consists of calling a request	200	Libeio has both a high-level API, which consists of calling a request
…		…
257	}	267	}
258		268
259	/* the first three arguments are passed to open(2) */	269	/* the first three arguments are passed to open(2) */
260	/* the remaining are priority, callback and data */	270	/* the remaining are priority, callback and data */
261	if (!eio_open ("/etc/passwd", O_RDONLY, 0, 0, file_open_done, 0))	271	if (!eio_open ("/etc/passwd", O_RDONLY, 0, 0, file_open_done, 0))
262	abort (); /* something ent wrong, we will all die!!! */	272	abort (); /* something went wrong, we will all die!!! */
263		273
264	Note that you additionally need to call C<eio_poll> when the C<want_cb>	274	Note that you additionally need to call C<eio_poll> when the C<want_cb>
265	indicates that requests are ready to be processed.	275	indicates that requests are ready to be processed.
		276
		277	=head2 CANCELLING REQUESTS
		278
		279	Sometimes the need for a request goes away before the request is
		280	finished. In that case, one can cancel the request by a call to
		281	C<eio_cancel>:
		282
		283	=over 4
		284
		285	=item eio_cancel (eio_req *req)
		286
		287	Cancel the request (and all its subrequests). If the request is currently
		288	executing it might still continue to execute, and in other cases it might
		289	still take a while till the request is cancelled.
		290
		291	Even if cancelled, the finish callback will still be invoked - the
		292	callbacks of all cancellable requests need to check whether the request
		293	has been cancelled by calling C<EIO_CANCELLED (req)>:
		294
		295	static int
		296	my_eio_cb (eio_req *req)
		297	{
		298	if (EIO_CANCELLED (req))
		299	return 0;
		300	}
		301
		302	In addition, cancelled requests will I<either> have C<< req->result >>
		303	set to C<-1> and C<errno> to C<ECANCELED>, or I<otherwise> they were
		304	successfully executed, despite being cancelled (e.g. when they have
		305	already been executed at the time they were cancelled).
		306
		307	C<EIO_CANCELLED> is still true for requests that have successfully
		308	executed, as long as C<eio_cancel> was called on them at some point.
		309
		310	=back
266		311
267	=head2 AVAILABLE REQUESTS	312	=head2 AVAILABLE REQUESTS
268		313
269	The following request functions are available. I<All> of them return the	314	The following request functions are available. I<All> of them return the
270	C<eio_req *> on success and C<0> on failure, and I<all> of them have the	315	C<eio_req *> on success and C<0> on failure, and I<all> of them have the
…		…
366	free (target);	411	free (target);
367	}	412	}
368		413
369	=item eio_realpath (const char path, int pri, eio_cb cb, void data)	414	=item eio_realpath (const char path, int pri, eio_cb cb, void data)
370		415
371	Similar to the realpath libc function, but unlike that one, result is	416	Similar to the realpath libc function, but unlike that one, C<<
372	C<-1> on failure and the length of the returned path in C<ptr2> (which is	417	req->result >> is C<-1> on failure. On success, the result is the length
373	not 0-terminated) - this is similar to readlink.	418	of the returned path in C<ptr2> (which is I<NOT> 0-terminated) - this is
		419	similar to readlink.
374		420
375	=item eio_stat (const char path, int pri, eio_cb cb, void data)	421	=item eio_stat (const char path, int pri, eio_cb cb, void data)
376		422
377	=item eio_lstat (const char path, int pri, eio_cb cb, void data)	423	=item eio_lstat (const char path, int pri, eio_cb cb, void data)
378		424
379	=item eio_fstat (int fd, int pri, eio_cb cb, void *data)	425	=item eio_fstat (int fd, int pri, eio_cb cb, void *data)
380		426
381	Stats a file - if C<< req->result >> indicates success, then you can	427	Stats a file - if C<< req->result >> indicates success, then you can
382	access the C<struct stat>-like structure via C<< req->ptr2 >>:	428	access the C<struct stat>-like structure via C<< req->ptr2 >>:
383		429
384	EIO_STRUCT_STAT statdata = (EIO_STRUCT_STAT )req->ptr2;	430	EIO_STRUCT_STAT statdata = (EIO_STRUCT_STAT )req->ptr2;
385		431
386	=item eio_statvfs (const char path, int pri, eio_cb cb, void data)	432	=item eio_statvfs (const char path, int pri, eio_cb cb, void data)
387		433
388	=item eio_fstatvfs (int fd, int pri, eio_cb cb, void *data)	434	=item eio_fstatvfs (int fd, int pri, eio_cb cb, void *data)
389		435
390	Stats a filesystem - if C<< req->result >> indicates success, then you can	436	Stats a filesystem - if C<< req->result >> indicates success, then you can
391	access the C<struct statvfs>-like structure via C<< req->ptr2 >>:	437	access the C<struct statvfs>-like structure via C<< req->ptr2 >>:
392		438
393	EIO_STRUCT_STATVFS statdata = (EIO_STRUCT_STATVFS )req->ptr2;	439	EIO_STRUCT_STATVFS statdata = (EIO_STRUCT_STATVFS )req->ptr2;
394		440
395	=back	441	=back
396		442
397	=head3 READING DIRECTORIES	443	=head3 READING DIRECTORIES
398		444
399	Reading directories sounds simple, but can be rather demanding, especially	445	Reading directories sounds simple, but can be rather demanding, especially
400	if you want to do stuff such as traversing a diretcory hierarchy or	446	if you want to do stuff such as traversing a directory hierarchy or
401	processing all files in a directory. Libeio can assist thess complex tasks	447	processing all files in a directory. Libeio can assist these complex tasks
402	with it's C<eio_readdir> call.	448	with it's C<eio_readdir> call.
403		449
404	=over 4	450	=over 4
405		451
406	=item eio_readdir (const char path, int flags, int pri, eio_cb cb, void data)	452	=item eio_readdir (const char path, int flags, int pri, eio_cb cb, void data)
…		…
438		484
439	If this flag is specified, then, in addition to the names in C<ptr2>,	485	If this flag is specified, then, in addition to the names in C<ptr2>,
440	also an array of C<struct eio_dirent> is returned, in C<ptr1>. A C<struct	486	also an array of C<struct eio_dirent> is returned, in C<ptr1>. A C<struct
441	eio_dirent> looks like this:	487	eio_dirent> looks like this:
442		488
443	struct eio_dirent	489	struct eio_dirent
444	{	490	{
445	int nameofs; /* offset of null-terminated name string in (char )req->ptr2 /	491	int nameofs; /* offset of null-terminated name string in (char )req->ptr2 /
446	unsigned short namelen; /* size of filename without trailing 0 */	492	unsigned short namelen; /* size of filename without trailing 0 */
447	unsigned char type; /* one of EIO_DT_* */	493	unsigned char type; /* one of EIO_DT_* */
448	signed char score; /* internal use */	494	signed char score; /* internal use */
449	ino_t inode; /* the inode number, if available, otherwise unspecified */	495	ino_t inode; /* the inode number, if available, otherwise unspecified */
450	};	496	};
451		497
452	The only members you normally would access are C<nameofs>, which is the	498	The only members you normally would access are C<nameofs>, which is the
453	byte-offset from C<ptr2> to the start of the name, C<namelen> and C<type>.	499	byte-offset from C<ptr2> to the start of the name, C<namelen> and C<type>.
454		500
455	C<type> can be one of:	501	C<type> can be one of:
…		…
498	When this flag is specified, then the names will be returned in an order	544	When this flag is specified, then the names will be returned in an order
499	suitable for stat()'ing each one. That is, when you plan to stat()	545	suitable for stat()'ing each one. That is, when you plan to stat()
500	all files in the given directory, then the returned order will likely	546	all files in the given directory, then the returned order will likely
501	be fastest.	547	be fastest.
502		548
503	If both this flag and C<EIO_READDIR_DIRS_FIRST> are specified, then	549	If both this flag and C<EIO_READDIR_DIRS_FIRST> are specified, then the
504	the likely dirs come first, resulting in a less optimal stat order.	550	likely directories come first, resulting in a less optimal stat order.
505		551
506	=item EIO_READDIR_FOUND_UNKNOWN	552	=item EIO_READDIR_FOUND_UNKNOWN
507		553
508	This flag should not be specified when calling C<eio_readdir>. Instead,	554	This flag should not be specified when calling C<eio_readdir>. Instead,
509	it is being set by C<eio_readdir> (you can access the C<flags> via C<<	555	it is being set by C<eio_readdir> (you can access the C<flags> via C<<
510	req->int1 >>, when any of the C<type>'s found were C<EIO_DT_UNKNOWN>. The	556	req->int1 >>, when any of the C<type>'s found were C<EIO_DT_UNKNOWN>. The
511	absense of this flag therefore indicates that all C<type>'s are known,	557	absence of this flag therefore indicates that all C<type>'s are known,
512	which can be used to speed up some algorithms.	558	which can be used to speed up some algorithms.
513		559
514	A typical use case would be to identify all subdirectories within a	560	A typical use case would be to identify all subdirectories within a
515	directory - you would ask C<eio_readdir> for C<EIO_READDIR_DIRS_FIRST>. If	561	directory - you would ask C<eio_readdir> for C<EIO_READDIR_DIRS_FIRST>. If
516	then this flag is I<NOT> set, then all the entries at the beginning of the	562	then this flag is I<NOT> set, then all the entries at the beginning of the
…		…
546	=item eio_readahead (int fd, off_t offset, size_t length, int pri, eio_cb cb, void *data)	592	=item eio_readahead (int fd, off_t offset, size_t length, int pri, eio_cb cb, void *data)
547		593
548	Calls C<readahead(2)>. If the syscall is missing, then the call is	594	Calls C<readahead(2)>. If the syscall is missing, then the call is
549	emulated by simply reading the data (currently in 64kiB chunks).	595	emulated by simply reading the data (currently in 64kiB chunks).
550		596
		597	=item eio_syncfs (int fd, int pri, eio_cb cb, void *data)
		598
		599	Calls Linux' C<syncfs> syscall, if available. Returns C<-1> and sets
		600	C<errno> to C<ENOSYS> if the call is missing I<but still calls sync()>,
		601	if the C<fd> is C<< >= 0 >>, so you can probe for the availability of the
		602	syscall with a negative C<fd> argument and checking for C<-1/ENOSYS>.
		603
551	=item eio_sync_file_range (int fd, off_t offset, size_t nbytes, unsigned int flags, int pri, eio_cb cb, void *data)	604	=item eio_sync_file_range (int fd, off_t offset, size_t nbytes, unsigned int flags, int pri, eio_cb cb, void *data)
552		605
553	Calls C<sync_file_range>. If the syscall is missing, then this is the same	606	Calls C<sync_file_range>. If the syscall is missing, then this is the same
554	as calling C<fdatasync>.	607	as calling C<fdatasync>.
555		608
556	Flags can be any combination of C<EIO_SYNC_FILE_RANGE_WAIT_BEFORE>,	609	Flags can be any combination of C<EIO_SYNC_FILE_RANGE_WAIT_BEFORE>,
557	C<EIO_SYNC_FILE_RANGE_WRITE> and C<EIO_SYNC_FILE_RANGE_WAIT_AFTER>.	610	C<EIO_SYNC_FILE_RANGE_WRITE> and C<EIO_SYNC_FILE_RANGE_WAIT_AFTER>.
		611
		612	=item eio_fallocate (int fd, int mode, off_t offset, off_t len, int pri, eio_cb cb, void *data)
		613
		614	Calls C<fallocate> (note: I<NOT> C<posix_fallocate>!). If the syscall is
		615	missing, then it returns failure and sets C<errno> to C<ENOSYS>.
		616
		617	The C<mode> argument can be C<0> (for behaviour similar to
		618	C<posix_fallocate>), or C<EIO_FALLOC_FL_KEEP_SIZE>, which keeps the size
		619	of the file unchanged (but still preallocates space beyond end of file).
558		620
559	=back	621	=back
560		622
561	=head3 LIBEIO-SPECIFIC REQUESTS	623	=head3 LIBEIO-SPECIFIC REQUESTS
562		624
…		…
604		666
605	eio_custom (my_open, 0, my_open_done, "/etc/passwd");	667	eio_custom (my_open, 0, my_open_done, "/etc/passwd");
606		668
607	=item eio_busy (eio_tstamp delay, int pri, eio_cb cb, void *data)	669	=item eio_busy (eio_tstamp delay, int pri, eio_cb cb, void *data)
608		670
609	This is a a request that takes C<delay> seconds to execute, but otherwise	671	This is a request that takes C<delay> seconds to execute, but otherwise
610	does nothing - it simply puts one of the worker threads to sleep for this	672	does nothing - it simply puts one of the worker threads to sleep for this
611	long.	673	long.
612		674
613	This request can be used to artificially increase load, e.g. for debugging	675	This request can be used to artificially increase load, e.g. for debugging
614	or benchmarking reasons.	676	or benchmarking reasons.
…		…
630	There are two primary use cases for this: a) bundle many requests into a	692	There are two primary use cases for this: a) bundle many requests into a
631	single, composite, request with a definite callback and the ability to	693	single, composite, request with a definite callback and the ability to
632	cancel the whole request with its subrequests and b) limiting the number	694	cancel the whole request with its subrequests and b) limiting the number
633	of "active" requests.	695	of "active" requests.
634		696
635	Further below you will find more dicussion of these topics - first follows	697	Further below you will find more discussion of these topics - first
636	the reference section detailing the request generator and other methods.	698	follows the reference section detailing the request generator and other
		699	methods.
637		700
638	=over 4	701	=over 4
639		702
640	=item eio_grp (eio_cb cb, void *data)	703	=item eio_req grp = eio_grp (eio_cb cb, void data)
641		704
642	Creates and submits a group request.	705	Creates, submits and returns a group request. Note that it doesn't have a
		706	priority, unlike all other requests.
643		707
644	=back	708	=item eio_grp_add (eio_req grp, eio_req req)
645		709
		710	Adds a request to the request group.
		711
		712	=item eio_grp_cancel (eio_req *grp)
		713
		714	Cancels all requests I<in> the group, but I<not> the group request
		715	itself. You can cancel the group request I<and> all subrequests via a
		716	normal C<eio_cancel> call.
		717
		718	=back
		719
		720	=head4 GROUP REQUEST LIFETIME
		721
		722	Left alone, a group request will instantly move to the pending state and
		723	will be finished at the next call of C<eio_poll>.
		724
		725	The usefulness stems from the fact that, if a subrequest is added to a
		726	group I<before> a call to C<eio_poll>, via C<eio_grp_add>, then the group
		727	will not finish until all the subrequests have finished.
		728
		729	So the usage cycle of a group request is like this: after it is created,
		730	you normally instantly add a subrequest. If none is added, the group
		731	request will finish on it's own. As long as subrequests are added before
		732	the group request is finished it will be kept from finishing, that is the
		733	callbacks of any subrequests can, in turn, add more requests to the group,
		734	and as long as any requests are active, the group request itself will not
		735	finish.
		736
		737	=head4 CREATING COMPOSITE REQUESTS
		738
		739	Imagine you wanted to create an C<eio_load> request that opens a file,
		740	reads it and closes it. This means it has to execute at least three eio
		741	requests, but for various reasons it might be nice if that request looked
		742	like any other eio request.
		743
		744	This can be done with groups:
		745
		746	=over 4
		747
		748	=item 1) create the request object
		749
		750	Create a group that contains all further requests. This is the request you
		751	can return as "the load request".
		752
		753	=item 2) open the file, maybe
		754
		755	Next, open the file with C<eio_open> and add the request to the group
		756	request and you are finished setting up the request.
		757
		758	If, for some reason, you cannot C<eio_open> (path is a null ptr?) you
		759	can set C<< grp->result >> to C<-1> to signal an error and let the group
		760	request finish on its own.
		761
		762	=item 3) open callback adds more requests
		763
		764	In the open callback, if the open was not successful, copy C<<
		765	req->errorno >> to C<< grp->errorno >> and set C<< grp->errorno >> to
		766	C<-1> to signal an error.
		767
		768	Otherwise, malloc some memory or so and issue a read request, adding the
		769	read request to the group.
		770
		771	=item 4) continue issuing requests till finished
		772
		773	In the real callback, check for errors and possibly continue with
		774	C<eio_close> or any other eio request in the same way.
		775
		776	As soon as no new requests are added the group request will finish. Make
		777	sure you I<always> set C<< grp->result >> to some sensible value.
		778
		779	=back
		780
		781	=head4 REQUEST LIMITING
646		782
647		783
648	#TODO	784	#TODO
649		785
650	/*****************************************************************************/
651	/* groups */
652
653	eio_req eio_grp (eio_cb cb, void data);
654	void eio_grp_feed (eio_req grp, void (feed)(eio_req *req), int limit);
655	void eio_grp_limit (eio_req *grp, int limit);	786	void eio_grp_limit (eio_req *grp, int limit);
656	void eio_grp_add (eio_req grp, eio_req req);
657	void eio_grp_cancel (eio_req grp); / cancels all sub requests but not the group */
658		787
659		788
660	=back	789	=back
661		790
662		791
…		…
668	=head1 ANATOMY AND LIFETIME OF AN EIO REQUEST	797	=head1 ANATOMY AND LIFETIME OF AN EIO REQUEST
669		798
670	A request is represented by a structure of type C<eio_req>. To initialise	799	A request is represented by a structure of type C<eio_req>. To initialise
671	it, clear it to all zero bytes:	800	it, clear it to all zero bytes:
672		801
673	eio_req req;	802	eio_req req;
674		803
675	memset (&req, 0, sizeof (req));	804	memset (&req, 0, sizeof (req));
676		805
677	A more common way to initialise a new C<eio_req> is to use C<calloc>:	806	A more common way to initialise a new C<eio_req> is to use C<calloc>:
678		807
679	eio_req req = calloc (1, sizeof (req));	808	eio_req req = calloc (1, sizeof (req));
680		809
681	In either case, libeio neither allocates, initialises or frees the	810	In either case, libeio neither allocates, initialises or frees the
682	C<eio_req> structure for you - it merely uses it.	811	C<eio_req> structure for you - it merely uses it.
683		812
684	zero	813	zero
…		…
702	for example, in interactive programs, you might want to limit this time to	831	for example, in interactive programs, you might want to limit this time to
703	C<0.01> seconds or so.	832	C<0.01> seconds or so.
704		833
705	Note that:	834	Note that:
706		835
		836	=over 4
		837
707	a) libeio doesn't know how long your request callbacks take, so the time	838	=item a) libeio doesn't know how long your request callbacks take, so the
708	spent in C<eio_poll> is up to one callback invocation longer then this	839	time spent in C<eio_poll> is up to one callback invocation longer then
709	interval.	840	this interval.
710		841
711	b) this is implemented by calling C<gettimeofday> after each request,	842	=item b) this is implemented by calling C<gettimeofday> after each
712	which can be costly.	843	request, which can be costly.
713		844
714	c) at least one request will be handled.	845	=item c) at least one request will be handled.
		846
		847	=back
715		848
716	=item eio_set_max_poll_reqs (unsigned int nreqs)	849	=item eio_set_max_poll_reqs (unsigned int nreqs)
717		850
718	When C<nreqs> is non-zero, then C<eio_poll> will not handle more than	851	When C<nreqs> is non-zero, then C<eio_poll> will not handle more than
719	C<nreqs> requests per invocation. This is a less costly way to limit the	852	C<nreqs> requests per invocation. This is a less costly way to limit the
…		…
789	This symbol governs the stack size for each eio thread. Libeio itself	922	This symbol governs the stack size for each eio thread. Libeio itself
790	was written to use very little stackspace, but when using C<EIO_CUSTOM>	923	was written to use very little stackspace, but when using C<EIO_CUSTOM>
791	requests, you might want to increase this.	924	requests, you might want to increase this.
792		925
793	If this symbol is undefined (the default) then libeio will use its default	926	If this symbol is undefined (the default) then libeio will use its default
794	stack size (C<sizeof (long) * 4096> currently). If it is defined, but	927	stack size (C<sizeof (void ) 4096> currently). If it is defined, but
795	C<0>, then the default operating system stack size will be used. In all	928	C<0>, then the default operating system stack size will be used. In all
796	other cases, the value must be an expression that evaluates to the desired	929	other cases, the value must be an expression that evaluates to the desired
797	stack size.	930	stack size.
798		931
799	=back	932	=back

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Comparing libeio/eio.pod (file contents): Revision 1.15 by root, Tue Jul 5 16:57:41 2011 UTC vs. Revision 1.27 by root, Sun Jul 24 03:32:54 2011 UTC

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Comparing libeio/eio.pod (file contents):
Revision 1.15 by root, Tue Jul 5 16:57:41 2011 UTC vs.
Revision 1.27 by root, Sun Jul 24 03:32:54 2011 UTC