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number of semaphores and semaphore sets 3+ messages / 3 participants [nested] [flat]
* number of semaphores and semaphore sets @ 2011-03-21 16:05 Anton Yuzhaninov <[email protected]> 2011-04-05 16:57 ` Re: number of semaphores and semaphore sets Robert Haas <[email protected]> 0 siblings, 1 reply; 3+ messages in thread From: Anton Yuzhaninov @ 2011-03-21 16:05 UTC (permalink / raw) To: pgsql-docs This page: http://www.postgresql.org/docs/9.0/interactive/kernel-resources.html has formula: ceil((max_connections + autovacuum_max_workers) / 16) for number of semaphore sets (identifiers). It seems to be wrong (outdated). Correct formula seems to be ceil((max_connections + autovacuum_max_workers + 4) / 16) Semaphore sets created in src/backend/storage/lmgr/proc.c: 1. MaxConnections 2. autovacuum_max_workers + 1 3. NUM_AUXILIARY_PROCS (currently 3) -- Anton Yuzhaninov ^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: number of semaphores and semaphore sets 2011-03-21 16:05 number of semaphores and semaphore sets Anton Yuzhaninov <[email protected]> @ 2011-04-05 16:57 ` Robert Haas <[email protected]> 2011-09-06 15:08 ` Re: number of semaphores and semaphore sets Bruce Momjian <[email protected]> 0 siblings, 1 reply; 3+ messages in thread From: Robert Haas @ 2011-04-05 16:57 UTC (permalink / raw) To: Anton Yuzhaninov <[email protected]>; +Cc: pgsql-docs On Mon, Mar 21, 2011 at 12:05 PM, Anton Yuzhaninov <[email protected]> wrote: > This page: > http://www.postgresql.org/docs/9.0/interactive/kernel-resources.html > > has formula: > ceil((max_connections + autovacuum_max_workers) / 16) > > for number of semaphore sets (identifiers). > > It seems to be wrong (outdated). > > Correct formula seems to be > > ceil((max_connections + autovacuum_max_workers + 4) / 16) > > Semaphore sets created in src/backend/storage/lmgr/proc.c: > 1. MaxConnections > 2. autovacuum_max_workers + 1 > 3. NUM_AUXILIARY_PROCS (currently 3) Yeah, I think you're right. It appears that nothing material has changed here since 8.3, so I'm inclined to back-patch this doc fix back that far. Barring objections, I'll go change this. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company ^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: number of semaphores and semaphore sets 2011-03-21 16:05 number of semaphores and semaphore sets Anton Yuzhaninov <[email protected]> 2011-04-05 16:57 ` Re: number of semaphores and semaphore sets Robert Haas <[email protected]> @ 2011-09-06 15:08 ` Bruce Momjian <[email protected]> 0 siblings, 0 replies; 3+ messages in thread From: Bruce Momjian @ 2011-09-06 15:08 UTC (permalink / raw) To: Robert Haas <[email protected]>; +Cc: Anton Yuzhaninov <[email protected]>; pgsql-docs Robert Haas wrote: > On Mon, Mar 21, 2011 at 12:05 PM, Anton Yuzhaninov <[email protected]> wrote: > > This page: > > http://www.postgresql.org/docs/9.0/interactive/kernel-resources.html > > > > has formula: > > ceil((max_connections + autovacuum_max_workers) / 16) > > > > for number of semaphore sets (identifiers). > > > > It seems to be wrong (outdated). > > > > Correct formula seems to be > > > > ceil((max_connections + autovacuum_max_workers + 4) / 16) > > > > Semaphore sets created in src/backend/storage/lmgr/proc.c: > > 1. MaxConnections > > 2. autovacuum_max_workers + 1 > > 3. NUM_AUXILIARY_PROCS (currently 3) > > Yeah, I think you're right. It appears that nothing material has > changed here since 8.3, so I'm inclined to back-patch this doc fix > back that far. > > Barring objections, I'll go change this. I have applied the attached patch and backpatched it to 9.0 and 9.1. -- Bruce Momjian <[email protected]> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. + Attachments: [text/x-diff] /rtmp/semaphore (2.3K, 2-%2Frtmp%2Fsemaphore) download | inline diff: diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml new file mode 100644 index 5098aad..68ceff1 *** a/doc/src/sgml/runtime.sgml --- b/doc/src/sgml/runtime.sgml *************** psql: could not connect to server: No su *** 604,616 **** <row> <entry><varname>SEMMNI</></> <entry>Maximum number of semaphore identifiers (i.e., sets)</> ! <entry>at least <literal>ceil((max_connections + autovacuum_max_workers) / 16)</literal></> </row> <row> <entry><varname>SEMMNS</></> <entry>Maximum number of semaphores system-wide</> ! <entry><literal>ceil((max_connections + autovacuum_max_workers) / 16) * 17</literal> plus room for other applications</> </row> <row> --- 604,616 ---- <row> <entry><varname>SEMMNI</></> <entry>Maximum number of semaphore identifiers (i.e., sets)</> ! <entry>at least <literal>ceil((max_connections + autovacuum_max_workers + 4) / 16)</literal></> </row> <row> <entry><varname>SEMMNS</></> <entry>Maximum number of semaphores system-wide</> ! <entry><literal>ceil((max_connections + autovacuum_max_workers + 4) / 16) * 17</literal> plus room for other applications</> </row> <row> *************** psql: could not connect to server: No su *** 685,691 **** linkend="sysvipc-parameters">). The parameter <varname>SEMMNI</> determines the limit on the number of semaphore sets that can exist on the system at one time. Hence this parameter must be at ! least <literal>ceil((max_connections + autovacuum_max_workers) / 16)</>. Lowering the number of allowed connections is a temporary workaround for failures, which are usually confusingly worded <quote>No space --- 685,691 ---- linkend="sysvipc-parameters">). The parameter <varname>SEMMNI</> determines the limit on the number of semaphore sets that can exist on the system at one time. Hence this parameter must be at ! least <literal>ceil((max_connections + autovacuum_max_workers + 4) / 16)</>. Lowering the number of allowed connections is a temporary workaround for failures, which are usually confusingly worded <quote>No space ^ permalink raw reply [nested|flat] 3+ messages in thread
end of thread, other threads:[~2011-09-06 15:08 UTC | newest] Thread overview: 3+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2011-03-21 16:05 number of semaphores and semaphore sets Anton Yuzhaninov <[email protected]> 2011-04-05 16:57 ` Robert Haas <[email protected]> 2011-09-06 15:08 ` Bruce Momjian <[email protected]>
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