diff options
| -rw-r--r-- | doc/src/sgml/runtime.sgml | 15 |
1 files changed, 9 insertions, 6 deletions
diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml index 0db38074644..59909059f17 100644 --- a/doc/src/sgml/runtime.sgml +++ b/doc/src/sgml/runtime.sgml @@ -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 + number of background 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 + number of background processes + 5) / 16) * 17</literal> plus room for other applications</> </row> <row> @@ -699,20 +699,23 @@ 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 processes requesting shared memory access, 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 number of background + processes requesting shared memory access, 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 + + number of background processes + 5) / 16)</>. Lowering the number of allowed connections is a temporary workaround for failures, which are usually confusingly worded <quote>No space |