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The formulas for SEMMNI and SEMMNS do not include the archiverprocess, which was converted to an auxiliary process in v14, andthe WAL summarizer process, which was introduced in v17. Thiscommit corrects these formulas and adds a missing reference tomax_wal_senders nearby. Since this section of the documentationtends to be incorrect quite often, we should likely give up ondocumenting the exact formulas in favor of something less fragile,but that is left as a future exercise.Reported-by: Sami ImseihReviewed-by: Sami ImseihDiscussion:https://postgr.es/m/20240517164452.GA1914161%40nathanxps13Backpatch-through: 12
Copy file name to clipboardExpand all lines: doc/src/sgml/runtime.sgml
+5-4Lines changed: 5 additions & 4 deletions
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@@ -781,13 +781,13 @@ psql: error: connection to server on socket "/tmp/.s.PGSQL.5432" failed: No such
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<row>
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<entry><varname>SEMMNI</varname></entry>
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<entry>Maximum number of semaphore identifiers (i.e., sets)</entry>
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<entry>at least <literal>ceil((max_connections + autovacuum_max_workers + max_wal_senders + max_worker_processes +5) / 16)</literal> plus room for other applications</entry>
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<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>
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</row>
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<row>
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<entry><varname>SEMMNS</varname></entry>
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<entry>Maximum number of semaphores system-wide</entry>
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<entry><literal>ceil((max_connections + autovacuum_max_workers + max_wal_senders + max_worker_processes +5) / 16) * 17</literal> plus room for other applications</entry>
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<entry><literal>ceil((max_connections + autovacuum_max_workers + max_wal_senders + max_worker_processes +7) / 16) * 17</literal> plus room for other applications</entry>
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</row>
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<row>
@@ -838,7 +838,8 @@ psql: error: connection to server on socket "/tmp/.s.PGSQL.5432" failed: No such
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When using System V semaphores,
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<productname>PostgreSQL</productname> uses one semaphore per allowed connection
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(<xref linkend="guc-max-connections"/>), allowed autovacuum worker process
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(<xref linkend="guc-autovacuum-max-workers"/>) and allowed background
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(<xref linkend="guc-autovacuum-max-workers"/>), allowed WAL sender process
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(<xref linkend="guc-max-wal-senders"/>), and allowed background
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process (<xref linkend="guc-max-worker-processes"/>), in sets of 16.
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Each such set will
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also contain a 17th semaphore which contains a <quote>magic
@@ -852,7 +853,7 @@ psql: error: connection to server on socket "/tmp/.s.PGSQL.5432" failed: No such
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linkend="sysvipc-parameters"/>). The parameter <varname>SEMMNI</varname>
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determines the limit on the number of semaphore sets that can
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exist on the system at one time. Hence this parameter must be at