[ViewVC] Diff of: cvs/AnyEvent-Fork-Pool/Pool.pm

Comparing AnyEvent-Fork-Pool/Pool.pm (file contents):
Revision 1.5 by root, Sat Apr 20 19:33:23 2013 UTC vs.
Revision 1.16 by root, Tue Jun 7 04:45:20 2016 UTC

…		…
3	AnyEvent::Fork::Pool - simple process pool manager on top of AnyEvent::Fork	3	AnyEvent::Fork::Pool - simple process pool manager on top of AnyEvent::Fork
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent;	7	use AnyEvent;
		8	use AnyEvent::Fork;
8	use AnyEvent::Fork::Pool;	9	use AnyEvent::Fork::Pool;
9	# use AnyEvent::Fork is not needed
10		10
11	# all parameters with default values	11	# all possible parameters shown, with default values
12	my $pool = AnyEvent::Fork	12	my $pool = AnyEvent::Fork
13	->new	13	->new
14	->require ("MyWorker")	14	->require ("MyWorker")
15	->AnyEvent::Fork::Pool::run (	15	->AnyEvent::Fork::Pool::run (
16	"MyWorker::run", # the worker function	16	"MyWorker::run", # the worker function
17		17
18	# pool management	18	# pool management
19	max => 4, # absolute maximum # of processes	19	max => 4, # absolute maximum # of processes
20	idle => 2, # minimum # of idle processes	20	idle => 0, # minimum # of idle processes
21	load => 2, # queue at most this number of jobs per process	21	load => 2, # queue at most this number of jobs per process
22	start => 0.1, # wait this many seconds before starting a new process	22	start => 0.1, # wait this many seconds before starting a new process
23	stop => 1, # wait this many seconds before stopping an idle process	23	stop => 10, # wait this many seconds before stopping an idle process
24	on_destroy => (my $finish = AE::cv), # called when object is destroyed	24	on_destroy => (my $finish = AE::cv), # called when object is destroyed
25		25
26	# parameters passed to AnyEvent::Fork::RPC	26	# parameters passed to AnyEvent::Fork::RPC
27	async => 0,	27	async => 0,
28	on_error => sub { die "FATAL: $_[0]\n" },	28	on_error => sub { die "FATAL: $_[0]\n" },
…		…
41		41
42	$finish->recv;	42	$finish->recv;
43		43
44	=head1 DESCRIPTION	44	=head1 DESCRIPTION
45		45
46	This module uses processes created via L<AnyEvent::Fork> and the RPC	46	This module uses processes created via L<AnyEvent::Fork> (or
47	protocol implement in L<AnyEvent::Fork::RPC> to create a load-balanced	47	L<AnyEvent::Fork::Remote>) and the RPC protocol implement in
48	pool of processes that handles jobs.	48	L<AnyEvent::Fork::RPC> to create a load-balanced pool of processes that
		49	handles jobs.
49		50
50	Understanding of L<AnyEvent::Fork> is helpful but not critical to be able	51	Understanding L<AnyEvent::Fork> is helpful but not required to use this
51	to use this module, but a thorough understanding of L<AnyEvent::Fork::RPC>	52	module, but a thorough understanding of L<AnyEvent::Fork::RPC> is, as
52	is, as it defines the actual API that needs to be implemented in the	53	it defines the actual API that needs to be implemented in the worker
53	children.	54	processes.
54
55	=head1 EXAMPLES
56		55
57	=head1 PARENT USAGE	56	=head1 PARENT USAGE
		57
		58	To create a pool, you first have to create a L<AnyEvent::Fork> object -
		59	this object becomes your template process. Whenever a new worker process
		60	is needed, it is forked from this template process. Then you need to
		61	"hand off" this template process to the C<AnyEvent::Fork::Pool> module by
		62	calling its run method on it:
		63
		64	my $template = AnyEvent::Fork
		65	->new
		66	->require ("SomeModule", "MyWorkerModule");
		67
		68	my $pool = $template->AnyEvent::Fork::Pool::run ("MyWorkerModule::myfunction");
		69
		70	The pool "object" is not a regular Perl object, but a code reference that
		71	you can call and that works roughly like calling the worker function
		72	directly, except that it returns nothing but instead you need to specify a
		73	callback to be invoked once results are in:
		74
		75	$pool->(1, 2, 3, sub { warn "myfunction(1,2,3) returned @_" });
58		76
59	=over 4	77	=over 4
60		78
61	=cut	79	=cut
62		80
…		…
68		86
69	use Guard ();	87	use Guard ();
70	use Array::Heap ();	88	use Array::Heap ();
71		89
72	use AnyEvent;	90	use AnyEvent;
73	use AnyEvent::Fork; # we don't actually depend on it, this is for convenience
74	use AnyEvent::Fork::RPC;	91	use AnyEvent::Fork::RPC;
75		92
76	# these are used for the first and last argument of events	93	# these are used for the first and last argument of events
77	# in the hope of not colliding. yes, I don't like it either,	94	# in the hope of not colliding. yes, I don't like it either,
78	# but didn't come up with an obviously better alternative.	95	# but didn't come up with an obviously better alternative.
79	my $magic0 = ':t6Z@HK1N%Dx@_7?=~-7NQgWDdAs6a,jFN=wLO0jD1%P';	96	my $magic0 = ':t6Z@HK1N%Dx@_7?=~-7NQgWDdAs6a,jFN=wLO0jD1%P';
80	my $magic1 = '<~53rexz.U`!]X[A235^"fyEoiTF\T~oH1l/N6+Djep9b~bI9`\1x%B~vWO1q*';	97	my $magic1 = '<~53rexz.U`!]X[A235^"fyEoiTF\T~oH1l/N6+Djep9b~bI9`\1x%B~vWO1q*';
81		98
82	our $VERSION = 0.1;	99	our $VERSION = 1.2;
83		100
84	=item my $pool = AnyEvent::Fork::Pool::run $fork, $function, [key => value...]	101	=item my $pool = AnyEvent::Fork::Pool::run $fork, $function, [key => value...]
85		102
86	The traditional way to call it. But it is way cooler to call it in the	103	The traditional way to call the pool creation function. But it is way
87	following way:	104	cooler to call it in the following way:
88		105
89	=item my $pool = $fork->AnyEvent::Fork::Pool::run ($function, [key => value...])	106	=item my $pool = $fork->AnyEvent::Fork::Pool::run ($function, [key => value...])
90		107
91	Creates a new pool object with the specified C<$function> as function	108	Creates a new pool object with the specified C<$function> as function
92	(name) to call for each request. The pool uses the C<$fork> object as the	109	(name) to call for each request. The pool uses the C<$fork> object as the
…		…
105		122
106	The pool consists of a certain number of worker processes. These options	123	The pool consists of a certain number of worker processes. These options
107	decide how many of these processes exist and when they are started and	124	decide how many of these processes exist and when they are started and
108	stopped.	125	stopped.
109		126
		127	The worker pool is dynamically resized, according to (perceived :)
		128	load. The minimum size is given by the C<idle> parameter and the maximum
		129	size is given by the C<max> parameter. A new worker is started every
		130	C<start> seconds at most, and an idle worker is stopped at most every
		131	C<stop> second.
		132
		133	You can specify the amount of jobs sent to a worker concurrently using the
		134	C<load> parameter.
		135
110	=over 4	136	=over 4
111		137
112	=item idle => $count (default: 0)	138	=item idle => $count (default: 0)
113		139
114	The minimum amount of idle processes in the pool - when there are fewer	140	The minimum amount of idle processes in the pool - when there are fewer
115	than this many idle workers, C<AnyEvent::Fork::Pool> will try to start new	141	than this many idle workers, C<AnyEvent::Fork::Pool> will try to start new
116	ones, subject to C<max> and C<start>.	142	ones, subject to the limits set by C<max> and C<start>.
117		143
118	This is also the initial/minimum amount of workers in the pool. The	144	This is also the initial amount of workers in the pool. The default of
119	default of zero means that the pool starts empty and can shrink back to	145	zero means that the pool starts empty and can shrink back to zero workers
120	zero workers over time.	146	over time.
121		147
122	=item max => $count (default: 4)	148	=item max => $count (default: 4)
123		149
124	The maximum number of processes in the pool, in addition to the template	150	The maximum number of processes in the pool, in addition to the template
125	process. C<AnyEvent::Fork::Pool> will never create more than this number	151	process. C<AnyEvent::Fork::Pool> will never have more than this number of
126	of worker processes, although there can be more temporarily when a worker	152	worker processes, although there can be more temporarily when a worker is
127	is shut down and hasn't exited yet.	153	shut down and hasn't exited yet.
128		154
129	=item load => $count (default: 2)	155	=item load => $count (default: 2)
130		156
131	The maximum number of concurrent jobs sent to a single worker	157	The maximum number of concurrent jobs sent to a single worker process.
132	process. Worker processes that handle this number of jobs already are
133	called "busy".
134		158
135	Jobs that cannot be sent to a worker immediately (because all workers are	159	Jobs that cannot be sent to a worker immediately (because all workers are
136	busy) will be queued until a worker is available.	160	busy) will be queued until a worker is available.
137		161
		162	Setting this low improves latency. For example, at C<1>, every job that
		163	is sent to a worker is sent to a completely idle worker that doesn't run
		164	any other jobs. The downside is that throughput is reduced - a worker that
		165	finishes a job needs to wait for a new job from the parent.
		166
		167	The default of C<2> is usually a good compromise.
		168
138	=item start => $seconds (default: 0.1)	169	=item start => $seconds (default: 0.1)
139		170
140	When a job is queued and all workers are busy, a timer is started. If the	171	When there are fewer than C<idle> workers (or all workers are completely
141	timer elapses and there are still jobs that cannot be queued to a worker,	172	busy), then a timer is started. If the timer elapses and there are still
142	a new worker is started.	173	jobs that cannot be queued to a worker, a new worker is started.
143		174
144	This configurs the time that all workers must be busy before a new worker	175	This sets the minimum time that all workers must be busy before a new
145	is started. Or, put differently, the minimum delay betwene starting new	176	worker is started. Or, put differently, the minimum delay between starting
146	workers.	177	new workers.
147		178
148	The delay is zero by default, which means new workers will be started	179	The delay is small by default, which means new workers will be started
149	without delay.	180	relatively quickly. A delay of C<0> is possible, and ensures that the pool
		181	will grow as quickly as possible under load.
150		182
		183	Non-zero values are useful to avoid "exploding" a pool because a lot of
		184	jobs are queued in an instant.
		185
		186	Higher values are often useful to improve efficiency at the cost of
		187	latency - when fewer processes can do the job over time, starting more and
		188	more is not necessarily going to help.
		189
151	=item stop => $seconds (default: 1)	190	=item stop => $seconds (default: 10)
152		191
153	When a worker has no jobs to execute it becomes idle. An idle worker that	192	When a worker has no jobs to execute it becomes idle. An idle worker that
154	hasn't executed a job within this amount of time will be stopped, unless	193	hasn't executed a job within this amount of time will be stopped, unless
155	the other parameters say otherwise.	194	the other parameters say otherwise.
156		195
		196	Setting this to a very high value means that workers stay around longer,
		197	even when they have nothing to do, which can be good as they don't have to
		198	be started on the netx load spike again.
		199
		200	Setting this to a lower value can be useful to avoid memory or simply
		201	process table wastage.
		202
		203	Usually, setting this to a time longer than the time between load spikes
		204	is best - if you expect a lot of requests every minute and little work
		205	in between, setting this to longer than a minute avoids having to stop
		206	and start workers. On the other hand, you have to ask yourself if letting
		207	workers run idle is a good use of your resources. Try to find a good
		208	balance between resource usage of your workers and the time to start new
		209	workers - the processes created by L<AnyEvent::Fork> itself is fats at
		210	creating workers while not using much memory for them, so most of the
		211	overhead is likely from your own code.
		212
157	=item on_destroy => $callback->() (default: none)	213	=item on_destroy => $callback->() (default: none)
158		214
159	When a pool object goes out of scope, it will still handle all outstanding	215	When a pool object goes out of scope, the outstanding requests are still
160	jobs. After that, it will destroy all workers (and also the template	216	handled till completion. Only after handling all jobs will the workers
161	process if it isn't referenced otherwise).	217	be destroyed (and also the template process if it isn't referenced
		218	otherwise).
		219
		220	To find out when a pool I<really> has finished its work, you can set this
		221	callback, which will be called when the pool has been destroyed.
162		222
163	=back	223	=back
164		224
165	=item Template Process	225	=item AnyEvent::Fork::RPC Parameters
166		226
167	The worker processes are all forked from a single template	227	These parameters are all passed more or less directly to
168	process. Ideally, all modules and all cdoe used by the worker, as well as	228	L<AnyEvent::Fork::RPC>. They are only briefly mentioned here, for
169	any shared data structures should be loaded into the template process, to	229	their full documentation please refer to the L<AnyEvent::Fork::RPC>
170	take advantage of data sharing via fork.	230	documentation. Also, the default values mentioned here are only documented
171		231	as a best effort - the L<AnyEvent::Fork::RPC> documentation is binding.
172	You can create your own template process by creating a L<AnyEvent::Fork>
173	object yourself and passing it as the C<template> parameter, but
174	C<AnyEvent::Fork::Pool> can create one for you, including some standard
175	options.
176		232
177	=over 4	233	=over 4
178		234
179	=item template => $fork (default: C<< AnyEvent::Fork->new >>)
180
181	The template process to use, if you want to create your own.
182
183	=item require => \@modules (default: C<[]>)
184
185	The modules in this list will be laoded into the template process.
186
187	=item eval => "# perl code to execute in template" (default: none)
188
189	This is a perl string that is evaluated after creating the template
190	process and after requiring the modules. It can do whatever it wants to
191	configure the process, but it must not do anything that would keep a later
192	fork from working (so must not create event handlers or (real) threads for
193	example).
194
195	=back
196
197	=item AnyEvent::Fork::RPC Parameters
198
199	These parameters are all passed directly to L<AnyEvent::Fork::RPC>. They
200	are only briefly mentioned here, for their full documentation
201	please refer to the L<AnyEvent::Fork::RPC> documentation. Also, the
202	default values mentioned here are only documented as a best effort -
203	L<AnyEvent::Fork::RPC> documentation is binding.
204
205	=over 4
206
207	=item async => $boolean (default: 0)	235	=item async => $boolean (default: 0)
208		236
209	Whether to sue the synchronous or asynchronous RPC backend.	237	Whether to use the synchronous or asynchronous RPC backend.
210		238
211	=item on_error => $callback->($message) (default: die with message)	239	=item on_error => $callback->($message) (default: die with message)
212		240
213	The callback to call on any (fatal) errors.	241	The callback to call on any (fatal) errors.
214		242
…		…
235		263
236	my $max = $arg{max} \|\| 4;	264	my $max = $arg{max} \|\| 4;
237	my $idle = $arg{idle} \|\| 0,	265	my $idle = $arg{idle} \|\| 0,
238	my $load = $arg{load} \|\| 2,	266	my $load = $arg{load} \|\| 2,
239	my $start = $arg{start} \|\| 0.1,	267	my $start = $arg{start} \|\| 0.1,
240	my $stop = $arg{stop} \|\| 1,	268	my $stop = $arg{stop} \|\| 10,
241	my $on_event = $arg{on_event} \|\| sub { },	269	my $on_event = $arg{on_event} \|\| sub { },
242	my $on_destroy = $arg{on_destroy};	270	my $on_destroy = $arg{on_destroy};
243		271
244	my @rpc = (	272	my @rpc = (
245	async => $arg{async},	273	async => $arg{async},
…		…
258		286
259	$template	287	$template
260	->require ("AnyEvent::Fork::RPC::" . ($arg{async} ? "Async" : "Sync"))	288	->require ("AnyEvent::Fork::RPC::" . ($arg{async} ? "Async" : "Sync"))
261	->eval ('	289	->eval ('
262	my ($magic0, $magic1) = @_;	290	my ($magic0, $magic1) = @_;
263	sub AnyEvent::Fork::Pool::quit() {	291	sub AnyEvent::Fork::Pool::retire() {
264	AnyEvent::Fork::RPC::on_event $magic0, "quit", $magic1;	292	AnyEvent::Fork::RPC::event $magic0, "quit", $magic1;
265	}	293	}
266	', $magic0, $magic1)	294	', $magic0, $magic1)
267	->eval ($arg{eval});	295	;
268		296
269	$start_worker = sub {	297	$start_worker = sub {
270	my $proc = [0, 0, undef]; # load, index, rpc	298	my $proc = [0, 0, undef]; # load, index, rpc
271		299
272	$proc->[2] = $template	300	$proc->[2] = $template
…		…
298	$proc->[0]	326	$proc->[0]
299	or --$nidle;	327	or --$nidle;
300		328
301	Array::Heap::splice_heap_idx @pool, $proc->[1]	329	Array::Heap::splice_heap_idx @pool, $proc->[1]
302	if defined $proc->[1];	330	if defined $proc->[1];
		331
		332	@$proc = 0; # tell others to leave it be
303	};	333	};
304		334
305	$want_start = sub {	335	$want_start = sub {
306	undef $stop_w;	336	undef $stop_w;
307		337
…		…
326	};	356	};
327		357
328	$scheduler = sub {	358	$scheduler = sub {
329	if (@queue) {	359	if (@queue) {
330	while (@queue) {	360	while (@queue) {
		361	@pool or $start_worker->();
		362
331	my $proc = $pool[0];	363	my $proc = $pool[0];
332		364
333	if ($proc->[0] < $load) {	365	if ($proc->[0] < $load) {
334	# found free worker, increase load	366	# found free worker, increase load
335	unless ($proc->[0]++) {	367	unless ($proc->[0]++) {
…		…
353	or $want_stop->();	385	or $want_stop->();
354		386
355	Array::Heap::adjust_heap_idx @pool, $proc->[1]	387	Array::Heap::adjust_heap_idx @pool, $proc->[1]
356	if defined $proc->[1];	388	if defined $proc->[1];
357		389
		390	&$ocb;
		391
358	$scheduler->();	392	$scheduler->();
359
360	&$ocb;
361	});	393	});
362	} else {	394	} else {
363	$want_start->()	395	$want_start->()
364	unless @pool >= $max;	396	unless @pool >= $max;
365		397
366	last;	398	last;
367	}	399	}
368	}	400	}
369	} elsif ($shutdown) {	401	} elsif ($shutdown) {
370	@pool = ();	402	undef $_->[2]
		403	for @pool;
		404
371	undef $start_w;	405	undef $start_w;
372	undef $start_worker; # frees $destroy_guard reference	406	undef $start_worker; # frees $destroy_guard reference
373		407
374	$stop_worker->($pool[0])	408	$stop_worker->($pool[0])
375	while $nidle;	409	while $nidle;
…		…
397		431
398	=item $pool->(..., $cb->(...))	432	=item $pool->(..., $cb->(...))
399		433
400	Call the RPC function of a worker with the given arguments, and when the	434	Call the RPC function of a worker with the given arguments, and when the
401	worker is done, call the C<$cb> with the results, just like calling the	435	worker is done, call the C<$cb> with the results, just like calling the
402	L<AnyEvent::Fork::RPC> object directly.	436	RPC object durectly - see the L<AnyEvent::Fork::RPC> documentation for
		437	details on the RPC API.
403		438
404	If there is no free worker, the call will be queued.	439	If there is no free worker, the call will be queued until a worker becomes
		440	available.
405		441
406	Note that there can be considerable time between calling this method and	442	Note that there can be considerable time between calling this method and
407	the call actually being executed. During this time, the parameters passed	443	the call actually being executed. During this time, the parameters passed
408	to this function are effectively read-only - modifying them after the call	444	to this function are effectively read-only - modifying them after the call
409	and before the callback is invoked causes undefined behaviour.	445	and before the callback is invoked causes undefined behaviour.
410		446
411	=cut	447	=cut
412		448
		449	=item $cpus = AnyEvent::Fork::Pool::ncpu [$default_cpus]
		450
		451	=item ($cpus, $eus) = AnyEvent::Fork::Pool::ncpu [$default_cpus]
		452
		453	Tries to detect the number of CPUs (C<$cpus> often called CPU cores
		454	nowadays) and execution units (C<$eus>) which include e.g. extra
		455	hyperthreaded units). When C<$cpus> cannot be determined reliably,
		456	C<$default_cpus> is returned for both values, or C<1> if it is missing.
		457
		458	For normal CPU bound uses, it is wise to have as many worker processes
		459	as CPUs in the system (C<$cpus>), if nothing else uses the CPU. Using
		460	hyperthreading is usually detrimental to performance, but in those rare
		461	cases where that really helps it might be beneficial to use more workers
		462	(C<$eus>).
		463
		464	Currently, F</proc/cpuinfo> is parsed on GNU/Linux systems for both
		465	C<$cpus> and C<$eus>, and on {Free,Net,Open}BSD, F<sysctl -n hw.ncpu> is
		466	used for C<$cpus>.
		467
		468	Example: create a worker pool with as many workers as CPU cores, or C<2>,
		469	if the actual number could not be determined.
		470
		471	$fork->AnyEvent::Fork::Pool::run ("myworker::function",
		472	max => (scalar AnyEvent::Fork::Pool::ncpu 2),
		473	);
		474
		475	=cut
		476
		477	BEGIN {
		478	if ($^O eq "linux") {
		479	*ncpu = sub(;$) {
		480	my ($cpus, $eus);
		481
		482	if (open my $fh, "<", "/proc/cpuinfo") {
		483	my %id;
		484
		485	while (<$fh>) {
		486	if (/^core id\s:\s(\d+)/) {
		487	++$eus;
		488	undef $id{$1};
		489	}
		490	}
		491
		492	$cpus = scalar keys %id;
		493	} else {
		494	$cpus = $eus = @_ ? shift : 1;
		495	}
		496	wantarray ? ($cpus, $eus) : $cpus
		497	};
		498	} elsif ($^O eq "freebsd" \|\| $^O eq "netbsd" \|\| $^O eq "openbsd") {
		499	*ncpu = sub(;$) {
		500	my $cpus = qx<sysctl -n hw.ncpu> * 1
		501	\|\| (@_ ? shift : 1);
		502	wantarray ? ($cpus, $cpus) : $cpus
		503	};
		504	} else {
		505	*ncpu = sub(;$) {
		506	my $cpus = @_ ? shift : 1;
		507	wantarray ? ($cpus, $cpus) : $cpus
		508	};
		509	}
		510	}
		511
413	=back	512	=back
414		513
		514	=head1 CHILD USAGE
		515
		516	In addition to the L<AnyEvent::Fork::RPC> API, this module implements one
		517	more child-side function:
		518
		519	=over 4
		520
		521	=item AnyEvent::Fork::Pool::retire ()
		522
		523	This function sends an event to the parent process to request retirement:
		524	the worker is removed from the pool and no new jobs will be sent to it,
		525	but it still has to handle the jobs that are already queued.
		526
		527	The parentheses are part of the syntax: the function usually isn't defined
		528	when you compile your code (because that happens I<before> handing the
		529	template process over to C<AnyEvent::Fork::Pool::run>, so you need the
		530	empty parentheses to tell Perl that the function is indeed a function.
		531
		532	Retiring a worker can be useful to gracefully shut it down when the worker
		533	deems this useful. For example, after executing a job, it could check the
		534	process size or the number of jobs handled so far, and if either is too
		535	high, the worker could request to be retired, to avoid memory leaks to
		536	accumulate.
		537
		538	Example: retire a worker after it has handled roughly 100 requests. It
		539	doesn't matter whether you retire at the beginning or end of your request,
		540	as the worker will continue to handle some outstanding requests. Likewise,
		541	it's ok to call retire multiple times.
		542
		543	my $count = 0;
		544
		545	sub my::worker {
		546
		547	++$count == 100
		548	and AnyEvent::Fork::Pool::retire ();
		549
		550	... normal code goes here
		551	}
		552
		553	=back
		554
		555	=head1 POOL PARAMETERS RECIPES
		556
		557	This section describes some recipes for pool parameters. These are mostly
		558	meant for the synchronous RPC backend, as the asynchronous RPC backend
		559	changes the rules considerably, making workers themselves responsible for
		560	their scheduling.
		561
		562	=over 4
		563
		564	=item low latency - set load = 1
		565
		566	If you need a deterministic low latency, you should set the C<load>
		567	parameter to C<1>. This ensures that never more than one job is sent to
		568	each worker. This avoids having to wait for a previous job to finish.
		569
		570	This makes most sense with the synchronous (default) backend, as the
		571	asynchronous backend can handle multiple requests concurrently.
		572
		573	=item lowest latency - set load = 1 and idle = max
		574
		575	To achieve the lowest latency, you additionally should disable any dynamic
		576	resizing of the pool by setting C<idle> to the same value as C<max>.
		577
		578	=item high throughput, cpu bound jobs - set load >= 2, max = #cpus
		579
		580	To get high throughput with cpu-bound jobs, you should set the maximum
		581	pool size to the number of cpus in your system, and C<load> to at least
		582	C<2>, to make sure there can be another job waiting for the worker when it
		583	has finished one.
		584
		585	The value of C<2> for C<load> is the minimum value that I<can> achieve
		586	100% throughput, but if your parent process itself is sometimes busy, you
		587	might need higher values. Also there is a limit on the amount of data that
		588	can be "in flight" to the worker, so if you send big blobs of data to your
		589	worker, C<load> might have much less of an effect.
		590
		591	=item high throughput, I/O bound jobs - set load >= 2, max = 1, or very high
		592
		593	When your jobs are I/O bound, using more workers usually boils down to
		594	higher throughput, depending very much on your actual workload - sometimes
		595	having only one worker is best, for example, when you read or write big
		596	files at maximum speed, as a second worker will increase seek times.
		597
		598	=back
		599
		600	=head1 EXCEPTIONS
		601
		602	The same "policy" as with L<AnyEvent::Fork::RPC> applies - exceptions
		603	will not be caught, and exceptions in both worker and in callbacks causes
		604	undesirable or undefined behaviour.
		605
415	=head1 SEE ALSO	606	=head1 SEE ALSO
416		607
417	L<AnyEvent::Fork>, to create the processes in the first place.	608	L<AnyEvent::Fork>, to create the processes in the first place.
		609
		610	L<AnyEvent::Fork::Remote>, likewise, but helpful for remote processes.
418		611
419	L<AnyEvent::Fork::RPC>, which implements the RPC protocol and API.	612	L<AnyEvent::Fork::RPC>, which implements the RPC protocol and API.
420		613
421	=head1 AUTHOR AND CONTACT INFORMATION	614	=head1 AUTHOR AND CONTACT INFORMATION
422		615

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Comparing AnyEvent-Fork-Pool/Pool.pm (file contents): Revision 1.5 by root, Sat Apr 20 19:33:23 2013 UTC vs. Revision 1.16 by root, Tue Jun 7 04:45:20 2016 UTC

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Comparing AnyEvent-Fork-Pool/Pool.pm (file contents):
Revision 1.5 by root, Sat Apr 20 19:33:23 2013 UTC vs.
Revision 1.16 by root, Tue Jun 7 04:45:20 2016 UTC