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| author | Thomas Munro <tmunro@postgresql.org> | 2020-07-31 17:27:09 +1200 |
|---|---|---|
| committer | Thomas Munro <tmunro@postgresql.org> | 2020-07-31 17:49:58 +1200 |
| commit | 84b1c63ad41872792d47e523363fce1f0e230022 (patch) | |
| tree | cc9ecdfd4f66edbcc5a1382598de5ba502023be9 /doc/src | |
| parent | 7b1110d2fd3da3d7536530d14952d4f4d9c25438 (diff) | |
| download | postgresql-84b1c63ad41872792d47e523363fce1f0e230022.tar.gz postgresql-84b1c63ad41872792d47e523363fce1f0e230022.zip | |
Preallocate some DSM space at startup.
Create an optional region in the main shared memory segment that can be
used to acquire and release "fast" DSM segments, and can benefit from
huge pages allocated at cluster startup time, if configured. Fall back
to the existing mechanisms when that space is full. The size is
controlled by a new GUC min_dynamic_shared_memory, defaulting to 0.
Main region DSM segments initially contain whatever garbage the memory
held last time they were used, rather than zeroes. That change revealed
that DSA areas failed to initialize themselves correctly in memory that
wasn't zeroed first, so fix that problem.
Discussion: https://postgr.es/m/CA%2BhUKGLAE2QBv-WgGp%2BD9P_J-%3Dyne3zof9nfMaqq1h3EGHFXYQ%40mail.gmail.com
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/config.sgml | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 427947cf496..994155ca00e 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -1906,6 +1906,30 @@ include_dir 'conf.d' </listitem> </varlistentry> + <varlistentry id="guc-min-dynamic-shared-memory" xreflabel="min_dynamic_shared_memory"> + <term><varname>min_dynamic_shared_memory</varname> (<type>integer</type>) + <indexterm> + <primary><varname>min_dynamic_shared_memory</varname> configuration parameter</primary> + </indexterm> + </term> + <listitem> + <para> + Specifies the amount of memory that should be allocated at server + startup time for use by parallel queries. When this memory region is + insufficient or exhausted by concurrent queries, new parallel queries + try to allocate extra shared memory temporarily from the operating + system using the method configured with + <varname>dynamic_shared_memory_type</varname>, which may be slower due + to memory management overheads. Memory that is allocated at startup + time with <varname>min_dynamic_shared_memory</varname> is affected by + the <varname>huge_pages</varname> setting on operating systems where + that is supported, and may be more likely to benefit from larger pages + on operating systems where that is managed automatically. + The default value is <literal>0</literal> (none). + </para> + </listitem> + </varlistentry> + </variablelist> </sect2> |