mirror of
https://git.postgresql.org/git/postgresql.git
synced 2024-09-04 15:27:21 +02:00
Correct the formulas for System V IPC parameters SEMMNI and SEMMNS in docs.
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:
parent
73ca21c7ac
commit
177ff78ddb
@ -645,13 +645,13 @@ 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 + max_worker_processes + 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 + max_worker_processes + 5) / 16) * 17</literal> plus room for other applications</>
|
||||
</row>
|
||||
|
||||
<row>
|
||||
@ -699,20 +699,22 @@ psql: could not connect to server: No such file or directory
|
||||
|
||||
<para>
|
||||
<productname>PostgreSQL</> uses one semaphore per allowed connection
|
||||
(<xref linkend="guc-max-connections">) and allowed autovacuum worker
|
||||
process (<xref linkend="guc-autovacuum-max-workers">), in sets of 16.
|
||||
(<xref linkend="guc-max-connections">), allowed autovacuum worker process
|
||||
(<xref linkend="guc-autovacuum-max-workers">) and allowed background
|
||||
process (<xref linkend="guc-max-worker-processes">), in sets of 16.
|
||||
Each such set will
|
||||
also contain a 17th semaphore which contains a <quote>magic
|
||||
number</quote>, to detect collision with semaphore sets used by
|
||||
other applications. The maximum number of semaphores in the system
|
||||
is set by <varname>SEMMNS</>, which consequently must be at least
|
||||
as high as <varname>max_connections</> plus
|
||||
<varname>autovacuum_max_workers</>, plus one extra for each 16
|
||||
<varname>autovacuum_max_workers</> plus <varname>max_worker_processes</>,
|
||||
plus one extra for each 16
|
||||
allowed connections plus workers (see the formula in <xref
|
||||
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 + max_worker_processes + 5) / 16)</>.
|
||||
Lowering the number
|
||||
of allowed connections is a temporary workaround for failures,
|
||||
which are usually confusingly worded <quote>No space
|
||||
|
Loading…
Reference in New Issue
Block a user