diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/config.sgml | 18 | ||||
| -rw-r--r-- | doc/src/sgml/runtime.sgml | 31 |
2 files changed, 37 insertions, 12 deletions
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 3dec0b7cfeb..57cd7bb9727 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -11145,6 +11145,24 @@ dynamic_library_path = 'C:\tools\postgresql;H:\my_project\lib;$libdir' </listitem> </varlistentry> + <varlistentry id="guc-num-os-semaphores" xreflabel="num_os_semaphores"> + <term><varname>num_os_semaphores</varname> (<type>integer</type>) + <indexterm> + <primary><varname>num_os_semaphores</varname> configuration parameter</primary> + </indexterm> + </term> + <listitem> + <para> + Reports the number of semaphores that are needed for the server based + on the configured number of allowed connections + (<xref linkend="guc-max-connections"/>), allowed autovacuum worker + processes (<xref linkend="guc-autovacuum-max-workers"/>), allowed WAL + sender processes (<xref linkend="guc-max-wal-senders"/>), allowed + background processes (<xref linkend="guc-max-worker-processes"/>), etc. + </para> + </listitem> + </varlistentry> + <varlistentry id="guc-segment-size" xreflabel="segment_size"> <term><varname>segment_size</varname> (<type>integer</type>) <indexterm> diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml index 2f7c6188869..2c4d5ef640d 100644 --- a/doc/src/sgml/runtime.sgml +++ b/doc/src/sgml/runtime.sgml @@ -781,13 +781,13 @@ psql: error: connection to server on socket "/tmp/.s.PGSQL.5432" failed: No such <row> <entry><varname>SEMMNI</varname></entry> <entry>Maximum number of semaphore identifiers (i.e., sets)</entry> - <entry>at least <literal>ceil((max_connections + autovacuum_max_workers + max_wal_senders + max_worker_processes + 7) / 16)</literal> plus room for other applications</entry> + <entry>at least <literal>ceil(num_os_semaphores / 16)</literal> plus room for other applications</entry> </row> <row> <entry><varname>SEMMNS</varname></entry> <entry>Maximum number of semaphores system-wide</entry> - <entry><literal>ceil((max_connections + autovacuum_max_workers + max_wal_senders + max_worker_processes + 7) / 16) * 17</literal> plus room for other applications</entry> + <entry><literal>ceil(num_os_semaphores / 16) * 17</literal> plus room for other applications</entry> </row> <row> @@ -839,21 +839,28 @@ psql: error: connection to server on socket "/tmp/.s.PGSQL.5432" failed: No such <productname>PostgreSQL</productname> uses one semaphore per allowed connection (<xref linkend="guc-max-connections"/>), allowed autovacuum worker process (<xref linkend="guc-autovacuum-max-workers"/>), allowed WAL sender process - (<xref linkend="guc-max-wal-senders"/>), and allowed background - process (<xref linkend="guc-max-worker-processes"/>), in sets of 16. - Each such set will + (<xref linkend="guc-max-wal-senders"/>), allowed background + process (<xref linkend="guc-max-worker-processes"/>), etc., in sets of 16. + The runtime-computed parameter <xref linkend="guc-num-os-semaphores"/> + reports the number of semaphores required. This parameter can be viewed + before starting the server with a <command>postgres</command> command like: +<programlisting> +$ <userinput>postgres -D $PGDATA -C num_os_semaphores</userinput> +</programlisting> + </para> + + <para> + Each set of 16 semaphores 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</varname>, which consequently must be at least - as high as <varname>max_connections</varname> plus - <varname>autovacuum_max_workers</varname> plus <varname>max_wal_senders</varname>, - plus <varname>max_worker_processes</varname>, plus one extra for each 16 - allowed connections plus workers (see the formula in <xref + as high as <literal>num_os_semaphores</literal> plus one extra for + each set of 16 required semaphores (see the formula in <xref linkend="sysvipc-parameters"/>). The parameter <varname>SEMMNI</varname> 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 + max_wal_senders + max_worker_processes + 7) / 16)</literal>. + least <literal>ceil(num_os_semaphores / 16)</literal>. Lowering the number of allowed connections is a temporary workaround for failures, which are usually confusingly worded <quote>No space @@ -885,8 +892,8 @@ psql: error: connection to server on socket "/tmp/.s.PGSQL.5432" failed: No such same as for System V, that is one semaphore per allowed connection (<xref linkend="guc-max-connections"/>), allowed autovacuum worker process (<xref linkend="guc-autovacuum-max-workers"/>), allowed WAL sender process - (<xref linkend="guc-max-wal-senders"/>), and allowed background - process (<xref linkend="guc-max-worker-processes"/>). + (<xref linkend="guc-max-wal-senders"/>), allowed background + process (<xref linkend="guc-max-worker-processes"/>), etc. On the platforms where this option is preferred, there is no specific kernel limit on the number of POSIX semaphores. </para> |