[ViewVC] Diff of: cvs/BDB/BDB.pm

Comparing BDB/BDB.pm (file contents):
Revision 1.4 by root, Mon Feb 5 23:46:15 2007 UTC vs.
Revision 1.22 by root, Mon Dec 10 03:57:27 2007 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use BDB;	7	use BDB;
8		8
		9	my $env = db_env_create;
		10
		11	mkdir "bdtest", 0700;
		12	db_env_open
		13	$env,
		14	"bdtest",
		15	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL
		16	\| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		17	0600;
		18
		19	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		20
		21	my $db = db_create $env;
		22	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE
		23	\| BDB::READ_UNCOMMITTED, 0600;
		24	db_put $db, undef, "key", "data", 0, sub {
		25	db_del $db, undef, "key";
		26	};
		27	db_sync $db;
		28
		29	# automatic result processing with AnyEvent:
		30	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		31	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		32
		33	# automatic result processing with EV:
		34	my $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb;
		35
		36	# with Glib:
		37	add_watch Glib::IO BDB::poll_fileno,
		38	in => sub { BDB::poll_cb; 1 };
		39
		40	# or simply flush manually
		41	BDB::flush;
		42
		43
9	=head1 DESCRIPTION	44	=head1 DESCRIPTION
10		45
11	=head2 EXAMPLE	46	See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>).
		47	The BDB API is very similar to the C API (the translation has been very faithful).
		48
		49	See also the example sections in the document below and possibly the eg/
		50	subdirectory of the BDB distribution. Last not least see the IO::AIO
		51	documentation, as that module uses almost the same asynchronous request
		52	model as this module.
		53
		54	I know this is woefully inadequate documentation. Send a patch!
		55
12		56
13	=head1 REQUEST ANATOMY AND LIFETIME	57	=head1 REQUEST ANATOMY AND LIFETIME
14		58
15	Every request method creates a request. which is a C data structure not	59	Every request method creates a request. which is a C data structure not
16	directly visible to Perl.	60	directly visible to Perl.
…		…
63	use strict 'vars';	107	use strict 'vars';
64		108
65	use base 'Exporter';	109	use base 'Exporter';
66		110
67	BEGIN {	111	BEGIN {
68	our $VERSION = '0.1';	112	our $VERSION = '1.3';
69		113
70	our @BDB_REQ = qw(	114	our @BDB_REQ = qw(
71	db_env_create db_env_open db_env_close	115	db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect
		116	db_env_memp_sync db_env_memp_trickle
72	db_create db_open db_close db_compact db_sync db_put db_get db_pget	117	db_open db_close db_compact db_sync db_put db_get db_pget db_del db_key_range
73	db_txn_commit db_txn_abort	118	db_txn_commit db_txn_abort db_txn_finish
		119	db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del
		120	db_sequence_open db_sequence_close
		121	db_sequence_get db_sequence_remove
74	);	122	);
75	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice));	123	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
		124	our @EXPORT_OK = qw(
76	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	125	poll_fileno poll_cb poll_wait flush
77	min_parallel max_parallel max_idle	126	min_parallel max_parallel max_idle
78	nreqs nready npending nthreads	127	nreqs nready npending nthreads
79	max_poll_time max_poll_reqs);	128	max_poll_time max_poll_reqs
		129	);
80		130
81	require XSLoader;	131	require XSLoader;
82	XSLoader::load ("BDB", $VERSION);	132	XSLoader::load ("BDB", $VERSION);
83	}	133	}
		134
		135	=head2 BERKELEYDB FUNCTIONS
		136
		137	All of these are functions. The create functions simply return a new
		138	object and never block. All the remaining functions all take an optional
		139	callback as last argument that gets passed the return value. If it is
		140	missing, then the function will be executed synchronously, and the return
		141	value is returned as normally.
		142
		143	BDB functions that cannot block (mostly functions that manipulate
		144	settings) are method calls on the relevant objects, so the rule of thumb
		145	is: if its a method, its not blocking, if its a function, it takes a
		146	callback as last argument.
		147
		148	In the following, C<$int> signifies an integer return value,
		149	C<octetstring> is a "binary string" (i.e. a perl string with no character
		150	indices >255), C<U32> is an unsigned 32 bit integer, C<int> is some
		151	integer, C<NV> is a floating point value.
		152
		153	The C<SV *> types are generic perl scalars (for input and output of data
		154	values), and the C<SV *callback> is the optional callback function to call
		155	when the request is completed.
		156
		157	The various C<DB_ENV> etc. arguments are handles return by
		158	C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an
		159	appended C<_ornull> this means they are optional and you can pass C<undef>
		160	for them, resulting a NULL pointer on the C level.
		161
		162	=head3 BDB functions
		163
		164	Functions in the BDB namespace, exported by default:
		165
		166	$env = db_env_create (U32 env_flags = 0)
		167	flags: RPCCLIENT
		168
		169	db_env_open (DB_ENV env, octetstring db_home, U32 open_flags, int mode, SV callback = &PL_sv_undef)
		170	open_flags: INIT_CDB INIT_LOCK INIT_LOG INIT_MPOOL INIT_REP INIT_TXN RECOVER RECOVER_FATAL USE_ENVIRON USE_ENVIRON_ROOT CREATE LOCKDOWN PRIVATE REGISTER SYSTEM_MEM
		171	db_env_close (DB_ENV env, U32 flags = 0, SV callback = &PL_sv_undef)
		172	db_env_txn_checkpoint (DB_ENV env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV callback = &PL_sv_undef)
		173	flags: FORCE
		174	db_env_lock_detect (DB_ENV env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV dummy = 0, SV *callback = &PL_sv_undef)
		175	atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST
		176	db_env_memp_sync (DB_ENV env, SV dummy = 0, SV *callback = &PL_sv_undef)
		177	db_env_memp_trickle (DB_ENV env, int percent, SV dummy = 0, SV *callback = &PL_sv_undef)
		178
		179	$db = db_create (DB_ENV *env = 0, U32 flags = 0)
		180	flags: XA_CREATE
		181
		182	db_open (DB db, DB_TXN_ornull txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef)
		183	flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE
		184	db_close (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		185	flags: DB_NOSYNC
		186	db_compact (DB db, DB_TXN_ornull txn = 0, SV start = 0, SV stop = 0, SV unused1 = 0, U32 flags = DB_FREE_SPACE, SV unused2 = 0, SV *callback = &PL_sv_undef)
		187	flags: FREELIST_ONLY FREE_SPACE
		188	db_sync (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		189	db_key_range (DB db, DB_TXN_ornull txn, SV key, SV key_range, U32 flags = 0, SV *callback = &PL_sv_undef)
		190	db_put (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		191	flags: APPEND NODUPDATA NOOVERWRITE
		192	db_get (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		193	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		194	db_pget (DB db, DB_TXN_ornull txn, SV key, SV pkey, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		195	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		196	db_del (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		197	db_txn_commit (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		198	flags: TXN_NOSYNC TXN_SYNC
		199	db_txn_abort (DB_TXN txn, SV callback = &PL_sv_undef)
		200
		201	db_c_close (DBC dbc, SV callback = &PL_sv_undef)
		202	db_c_count (DBC dbc, SV count, U32 flags = 0, SV *callback = &PL_sv_undef)
		203	db_c_put (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		204	flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
		205	db_c_get (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		206	flags: CURRENT FIRST GET_BOTH GET_BOTH_RANGE GET_RECNO JOIN_ITEM LAST NEXT NEXT_DUP NEXT_NODUP PREV PREV_DUP PREV_NODUP SET SET_RANGE SET_RECNO READ_UNCOMMITTED MULTIPLE MULTIPLE_KEY RMW
		207	db_c_pget (DBC dbc, SV key, SV pkey, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		208	db_c_del (DBC dbc, U32 flags = 0, SV callback = &PL_sv_undef)
		209
		210	db_sequence_open (DB_SEQUENCE seq, DB_TXN_ornull txnid, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		211	flags: CREATE EXCL
		212	db_sequence_close (DB_SEQUENCE seq, U32 flags = 0, SV callback = &PL_sv_undef)
		213	db_sequence_get (DB_SEQUENCE seq, DB_TXN_ornull txnid, int delta, SV seq_value, U32 flags = DB_TXN_NOSYNC, SV callback = &PL_sv_undef)
		214	flags: TXN_NOSYNC
		215	db_sequence_remove (DB_SEQUENCE seq, DB_TXN_ornull txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
		216	flags: TXN_NOSYNC
		217
		218	=head4 db_txn_finish (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		219
		220	This is not actually a Berkeley DB function but a BDB module
		221	extension. The background for this exytension is: It is very annoying to
		222	have to check every single BDB function for error returns and provide a
		223	codepath out of your transaction. While the BDB module still makes this
		224	possible, it contains the following extensions:
		225
		226	When a transaction-protected function returns any operating system
		227	error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
		228	transaction. This flag is also set by Berkeley DB functions themselves
		229	when an operation fails with LOCK_DEADLOCK, and it causes all further
		230	operations on that transaction (including C<db_txn_commit>) to fail.
		231
		232	The C<db_txn_finish> request will look at this flag, and, if it is set,
		233	will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
		234	if it isn't set to something else yet). If it isn't set, it will call
		235	C<db_txn_commit> and return the error normally.
		236
		237	How to use this? Easy: just write your transaction normally:
		238
		239	my $txn = $db_env->txn_begin;
		240	db_get $db, $txn, "key", my $data;
		241	db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
		242	db_txn_finish $txn;
		243	die "transaction failed" if $!;
		244
		245	That is, handle only the expected errors. If something unexpected happens
		246	(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
		247	requests (db_put in this case) will simply be skipped (they will fail with
		248	LOCK_DEADLOCK) and the transaction will be aborted.
		249
		250	You can use the C<< $txn->failed >> method to check wether a transaction
		251	has failed in this way and abort further processing (excluding
		252	C<db_txn_finish>).
		253
		254	=head3 DB_ENV/database environment methods
		255
		256	Methods available on DB_ENV/$env handles:
		257
		258	DESTROY (DB_ENV_ornull *env)
		259	CODE:
		260	if (env)
		261	env->close (env, 0);
		262
		263	$int = $env->set_data_dir (const char *dir)
		264	$int = $env->set_tmp_dir (const char *dir)
		265	$int = $env->set_lg_dir (const char *dir)
		266	$int = $env->set_shm_key (long shm_key)
		267	$int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		268	$int = $env->set_flags (U32 flags, int onoff)
		269	$env->set_errfile (FILE *errfile = 0)
		270	$env->set_msgfile (FILE *msgfile = 0)
		271	$int = $env->set_verbose (U32 which, int onoff = 1)
		272	$int = $env->set_encrypt (const char *password, U32 flags = 0)
		273	$int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		274	$int = $env->set_mp_max_openfd (int maxopenfd);
		275	$int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
		276	$int = $env->set_mp_mmapsize (int mmapsize_mb)
		277	$int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
		278	$int = $env->set_lk_max_lockers (U32 max)
		279	$int = $env->set_lk_max_locks (U32 max)
		280	$int = $env->set_lk_max_objects (U32 max)
		281	$int = $env->set_lg_bsize (U32 max)
		282	$int = $env->set_lg_max (U32 max)
		283	$int = $env->mutex_set_increment (U32 increment)
		284	$int = $env->mutex_set_tas_spins (U32 tas_spins)
		285	$int = $env->mutex_set_max (U32 max)
		286	$int = $env->mutex_set_align (U32 align)
		287
		288	$txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
		289	flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
		290
		291	=head4 Example:
		292
		293	use AnyEvent;
		294	use BDB;
		295
		296	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		297	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		298
		299	BDB::min_parallel 8;
		300
		301	my $env = db_env_create;
		302
		303	mkdir "bdtest", 0700;
		304	db_env_open
		305	$env,
		306	"bdtest",
		307	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL \| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		308	0600;
		309
		310	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		311
		312
		313	=head3 DB/database methods
		314
		315	Methods available on DB/$db handles:
		316
		317	DESTROY (DB_ornull *db)
		318	CODE:
		319	if (db)
		320	{
		321	SV env = (SV )db->app_private;
		322	db->close (db, 0);
		323	SvREFCNT_dec (env);
		324	}
		325
		326	$int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		327	$int = $db->set_flags (U32 flags)
		328	flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
		329	Btree: DUP DUPSORT RECNUM REVSPLITOFF
		330	Hash: DUP DUPSORT
		331	Queue: INORDER
		332	Recno: RENUMBER SNAPSHOT
		333
		334	$int = $db->set_encrypt (const char *password, U32 flags)
		335	$int = $db->set_lorder (int lorder)
		336	$int = $db->set_bt_minkey (U32 minkey)
		337	$int = $db->set_re_delim (int delim)
		338	$int = $db->set_re_pad (int re_pad)
		339	$int = $db->set_re_source (char *source)
		340	$int = $db->set_re_len (U32 re_len)
		341	$int = $db->set_h_ffactor (U32 h_ffactor)
		342	$int = $db->set_h_nelem (U32 h_nelem)
		343	$int = $db->set_q_extentsize (U32 extentsize)
		344
		345	$dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
		346	flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
		347	$seq = $db->sequence (U32 flags = 0)
		348
		349	=head4 Example:
		350
		351	my $db = db_create $env;
		352	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE \| BDB::READ_UNCOMMITTED, 0600;
		353
		354	for (1..1000) {
		355	db_put $db, undef, "key $_", "data $_";
		356
		357	db_key_range $db, undef, "key $_", my $keyrange;
		358	my ($lt, $eq, $gt) = @$keyrange;
		359	}
		360
		361	db_del $db, undef, "key $_" for 1..1000;
		362
		363	db_sync $db;
		364
		365
		366	=head3 DB_TXN/transaction methods
		367
		368	Methods available on DB_TXN/$txn handles:
		369
		370	DESTROY (DB_TXN_ornull *txn)
		371	CODE:
		372	if (txn)
		373	txn->abort (txn);
		374
		375	$int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		376	flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
		377
		378	$bool = $txn->failed
		379	# see db_txn_finish documentation, above
		380
		381
		382	=head3 DBC/cursor methods
		383
		384	Methods available on DBC/$dbc handles:
		385
		386	DESTROY (DBC_ornull *dbc)
		387	CODE:
		388	if (dbc)
		389	dbc->c_close (dbc);
		390
		391	=head4 Example:
		392
		393	my $c = $db->cursor;
		394
		395	for (;;) {
		396	db_c_get $c, my $key, my $data, BDB::NEXT;
		397	warn "<$!,$key,$data>";
		398	last if $!;
		399	}
		400
		401	db_c_close $c;
		402
		403
		404	=head3 DB_SEQUENCE/sequence methods
		405
		406	Methods available on DB_SEQUENCE/$seq handles:
		407
		408	DESTROY (DB_SEQUENCE_ornull *seq)
		409	CODE:
		410	if (seq)
		411	seq->close (seq, 0);
		412
		413	$int = $seq->initial_value (db_seq_t value)
		414	$int = $seq->set_cachesize (U32 size)
		415	$int = $seq->set_flags (U32 flags)
		416	flags: SEQ_DEC SEQ_INC SEQ_WRAP
		417	$int = $seq->set_range (db_seq_t min, db_seq_t max)
		418
		419	=head4 Example:
		420
		421	my $seq = $db->sequence;
		422
		423	db_sequence_open $seq, undef, "seq", BDB::CREATE;
		424	db_sequence_get $seq, undef, 1, my $value;
		425
84		426
85	=head2 SUPPORT FUNCTIONS	427	=head2 SUPPORT FUNCTIONS
86		428
87	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	429	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
88		430
…		…
133	interactiveness when perl is not fast enough to process all requests in	475	interactiveness when perl is not fast enough to process all requests in
134	time.	476	time.
135		477
136	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	478	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
137		479
138	Example: Install an Event watcher that automatically calls	480	Example: Install an EV watcher that automatically calls
139	BDB::poll_cb with low priority, to ensure that other parts of the	481	BDB::poll_cb with low priority, to ensure that other parts of the
140	program get the CPU sometimes even under high AIO load.	482	program get the CPU sometimes even under high load.
141		483
142	# try not to spend much more than 0.1s in poll_cb	484	# try not to spend much more than 0.1s in poll_cb
143	BDB::max_poll_time 0.1;	485	BDB::max_poll_time 0.1;
144		486
145	# use a low priority so other tasks have priority	487	my $bdb_poll = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb);
146	Event->io (fd => BDB::poll_fileno,
147	poll => 'r', nice => 1,
148	cb => &BDB::poll_cb);
149		488
150	=item BDB::poll_wait	489	=item BDB::poll_wait
151		490
152	If there are any outstanding requests and none of them in the result	491	If there are any outstanding requests and none of them in the result
153	phase, wait till the result filehandle becomes ready for reading (simply	492	phase, wait till the result filehandle becomes ready for reading (simply
…		…
165		504
166	BDB::poll_wait, BDB::poll_cb	505	BDB::poll_wait, BDB::poll_cb
167		506
168	=item BDB::flush	507	=item BDB::flush
169		508
170	Wait till all outstanding AIO requests have been handled.	509	Wait till all outstanding BDB requests have been handled.
171		510
172	Strictly equivalent to:	511	Strictly equivalent to:
173		512
174	BDB::poll_wait, BDB::poll_cb	513	BDB::poll_wait, BDB::poll_cb
175	while BDB::nreqs;	514	while BDB::nreqs;
176		515
		516	=back
		517
177	=head3 CONTROLLING THE NUMBER OF THREADS	518	=head3 CONTROLLING THE NUMBER OF THREADS
178		519
		520	=over 4
		521
179	=item BDB::min_parallel $nthreads	522	=item BDB::min_parallel $nthreads
180		523
181	Set the minimum number of AIO threads to C<$nthreads>. The current	524	Set the minimum number of BDB threads to C<$nthreads>. The current
182	default is C<8>, which means eight asynchronous operations can execute	525	default is C<8>, which means eight asynchronous operations can execute
183	concurrently at any one time (the number of outstanding requests,	526	concurrently at any one time (the number of outstanding requests,
184	however, is unlimited).	527	however, is unlimited).
185		528
186	BDB starts threads only on demand, when an AIO request is queued and	529	BDB starts threads only on demand, when an BDB request is queued and
187	no free thread exists. Please note that queueing up a hundred requests can	530	no free thread exists. Please note that queueing up a hundred requests can
188	create demand for a hundred threads, even if it turns out that everything	531	create demand for a hundred threads, even if it turns out that everything
189	is in the cache and could have been processed faster by a single thread.	532	is in the cache and could have been processed faster by a single thread.
190		533
191	It is recommended to keep the number of threads relatively low, as some	534	It is recommended to keep the number of threads relatively low, as some
…		…
196	Under most circumstances you don't need to call this function, as the	539	Under most circumstances you don't need to call this function, as the
197	module selects a default that is suitable for low to moderate load.	540	module selects a default that is suitable for low to moderate load.
198		541
199	=item BDB::max_parallel $nthreads	542	=item BDB::max_parallel $nthreads
200		543
201	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	544	Sets the maximum number of BDB threads to C<$nthreads>. If more than the
202	specified number of threads are currently running, this function kills	545	specified number of threads are currently running, this function kills
203	them. This function blocks until the limit is reached.	546	them. This function blocks until the limit is reached.
204		547
205	While C<$nthreads> are zero, aio requests get queued but not executed	548	While C<$nthreads> are zero, aio requests get queued but not executed
206	until the number of threads has been increased again.	549	until the number of threads has been increased again.
…		…
309		652
310	=head2 FORK BEHAVIOUR	653	=head2 FORK BEHAVIOUR
311		654
312	This module should do "the right thing" when the process using it forks:	655	This module should do "the right thing" when the process using it forks:
313		656
314	Before the fork, IO::AIO enters a quiescent state where no requests	657	Before the fork, BDB enters a quiescent state where no requests
315	can be added in other threads and no results will be processed. After	658	can be added in other threads and no results will be processed. After
316	the fork the parent simply leaves the quiescent state and continues	659	the fork the parent simply leaves the quiescent state and continues
317	request/result processing, while the child frees the request/result queue	660	request/result processing, while the child frees the request/result queue
318	(so that the requests started before the fork will only be handled in the	661	(so that the requests started before the fork will only be handled in the
319	parent). Threads will be started on demand until the limit set in the	662	parent). Threads will be started on demand until the limit set in the
320	parent process has been reached again.	663	parent process has been reached again.
321		664
322	In short: the parent will, after a short pause, continue as if fork had	665	In short: the parent will, after a short pause, continue as if fork had
323	not been called, while the child will act as if IO::AIO has not been used	666	not been called, while the child will act as if BDB has not been used
324	yet.	667	yet.
325		668
326	=head2 MEMORY USAGE	669	=head2 MEMORY USAGE
327		670
328	Per-request usage:	671	Per-request usage:
…		…
331	bytes of memory. In addition, stat requests need a stat buffer (possibly	674	bytes of memory. In addition, stat requests need a stat buffer (possibly
332	a few hundred bytes), readdir requires a result buffer and so on. Perl	675	a few hundred bytes), readdir requires a result buffer and so on. Perl
333	scalars and other data passed into aio requests will also be locked and	676	scalars and other data passed into aio requests will also be locked and
334	will consume memory till the request has entered the done state.	677	will consume memory till the request has entered the done state.
335		678
336	This is now awfully much, so queuing lots of requests is not usually a	679	This is not awfully much, so queuing lots of requests is not usually a
337	problem.	680	problem.
338		681
339	Per-thread usage:	682	Per-thread usage:
340		683
341	In the execution phase, some aio requests require more memory for	684	In the execution phase, some aio requests require more memory for
342	temporary buffers, and each thread requires a stack and other data	685	temporary buffers, and each thread requires a stack and other data
343	structures (usually around 16k-128k, depending on the OS).	686	structures (usually around 16k-128k, depending on the OS).
344		687
345	=head1 KNOWN BUGS	688	=head1 KNOWN BUGS
346		689
347	Known bugs will be fixed in the next release.	690	Known bugs will be fixed in the next release, except:
		691
		692	If you use a transaction in any request, and the request returns
		693	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		694	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		695	above.
348		696
349	=head1 SEE ALSO	697	=head1 SEE ALSO
350		698
351	L<Coro::AIO>.	699	L<Coro::BDB>, L<IO::AIO>.
352		700
353	=head1 AUTHOR	701	=head1 AUTHOR
354		702
355	Marc Lehmann <schmorp@schmorp.de>	703	Marc Lehmann <schmorp@schmorp.de>
356	http://home.schmorp.de/	704	http://home.schmorp.de/

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Comparing BDB/BDB.pm (file contents): Revision 1.4 by root, Mon Feb 5 23:46:15 2007 UTC vs. Revision 1.22 by root, Mon Dec 10 03:57:27 2007 UTC

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Comparing BDB/BDB.pm (file contents):
Revision 1.4 by root, Mon Feb 5 23:46:15 2007 UTC vs.
Revision 1.22 by root, Mon Dec 10 03:57:27 2007 UTC