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Correct the formulas for System V IPC parameters SEMMNI and SEMMNS in docs.

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In runtime.sgml, the old formulas for calculating the reasonable
values of SEMMNI and SEMMNS were incorrect. They have forgotten to
count the number of semaphores which both the checkpointer process
(introduced in 9.2) and the background worker processes (introduced
in 9.3) need.

This commit fixes those formulas so that they count the number of
semaphores which the checkpointer process and the background worker
processes need.

Report and patch by Kyotaro Horiguchi. Only the patch for 9.3 was
modified by me. Back-patch to 9.2 where the checkpointer process was
added and the number of needed semaphores was increased.

Author: Kyotaro Horiguchi
Reviewed-by: Fujii Masao
Backpatch: 9.2
Discussion: http://www.postgresql.org/message-id/20160203.125119.66820697.horiguchi.kyotaro@lab.ntt.co.jp
This commit is contained in:
Fujii Masao
2016-02-16 15:05:30 +09:00
parent daac53779a
commit 8a96651caa
1 changed files with 3 additions and 3 deletions
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6
doc/src/sgml/runtime.sgml
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@ -640,13 +640,13 @@ psql: could not connect to server: No such file or directory
<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></>
<entry>at least <literal>ceil((max_connections + autovacuum_max_workers + 5) / 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</>
<entry><literal>ceil((max_connections + autovacuum_max_workers + 5) / 16) * 17</literal> plus room for other applications</>
</row>
<row>
@ -721,7 +721,7 @@ psql: could not connect to server: No such file or directory
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)</>.
least <literal>ceil((max_connections + autovacuum_max_workers + 5) / 16)</>.
Lowering the number
of allowed connections is a temporary workaround for failures,
which are usually confusingly worded <quote>No space