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| author | Nathan Bossart <nathan@postgresql.org> | 2024-06-03 12:10:43 -0500 |
|---|---|---|
| committer | Nathan Bossart <nathan@postgresql.org> | 2024-06-03 12:10:43 -0500 |
| commit | 4ebe51a5fbc3e08861db85fe3868c31c6bc8ed59 (patch) | |
| tree | 60cd5715f0cfad0e4144040a13dc4de38f667fed /doc/src | |
| parent | 8fea1bd5411b793697a4c9087c403887e050c4ac (diff) | |
| download | postgresql-4ebe51a5fbc3e08861db85fe3868c31c6bc8ed59.tar.gz postgresql-4ebe51a5fbc3e08861db85fe3868c31c6bc8ed59.zip | |
Fix documentation for System V semaphores.
The formulas for SEMMNI and SEMMNS do not include the archiver
process, which was converted to an auxiliary process in v14, and
the WAL summarizer process, which was introduced in v17. This
commit corrects these formulas and adds a missing reference to
max_wal_senders nearby. Since this section of the documentation
tends to be incorrect quite often, we should likely give up on
documenting the exact formulas in favor of something less fragile,
but that is left as a future exercise.
Reported-by: Sami Imseih
Reviewed-by: Sami Imseih
Discussion: https://postgr.es/m/20240517164452.GA1914161%40nathanxps13
Backpatch-through: 12
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/runtime.sgml | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml index 6047b8171d4..883a849e6f5 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 + 5) / 16)</literal> plus room for other applications</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> </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 + 5) / 16) * 17</literal> plus room for other applications</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> </row> <row> @@ -838,7 +838,8 @@ psql: error: connection to server on socket "/tmp/.s.PGSQL.5432" failed: No such When using System V semaphores, <productname>PostgreSQL</productname> uses one semaphore per allowed connection (<xref linkend="guc-max-connections"/>), allowed autovacuum worker process - (<xref linkend="guc-autovacuum-max-workers"/>) and allowed background + (<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 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 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 + 5) / 16)</literal>. + least <literal>ceil((max_connections + autovacuum_max_workers + max_wal_senders + max_worker_processes + 7) / 16)</literal>. Lowering the number of allowed connections is a temporary workaround for failures, which are usually confusingly worded <quote>No space |