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| author | Peter Eisentraut <peter_e@gmx.net> | 2018-01-25 11:14:24 -0500 |
|---|---|---|
| committer | Peter Eisentraut <peter_e@gmx.net> | 2018-01-25 11:15:03 -0500 |
| commit | 2a5ecb56d22340a00393fa60e7b910c472071875 (patch) | |
| tree | b90dea3be7c09312ecdad040ba2025ade255ef4d | |
| parent | 0b5e33f667a2042d7022da8bef31a8be5937aad1 (diff) | |
| download | postgresql-2a5ecb56d22340a00393fa60e7b910c472071875.tar.gz postgresql-2a5ecb56d22340a00393fa60e7b910c472071875.zip | |
Update documentation to mention huge pages on other OSes
Previously, the docs implied that only Linux and Windows could use huge
pages. That's not quite true: it's just that we only know how to
request them explicitly on those OSes. Be more explicit about what
huge_pages really does and mention that some OSes may use huge pages
automatically.
Author: Thomas Munro and Catalin Iacob
Reviewed-By: Justin Pryzby, Peter Eisentraut
Discussion: https://postgr.es/m/CAEepm=3qzR-hfjepymohuC4XO5phxoSoipOjm6BEhnJHjNR+jg@mail.gmail.com
| -rw-r--r-- | doc/src/sgml/config.sgml | 33 |
1 files changed, 23 insertions, 10 deletions
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 45b2af14eb9..f951ddb41e7 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -1372,14 +1372,20 @@ include_dir 'conf.d' </term> <listitem> <para> - Enables/disables the use of huge memory pages. Valid values are - <literal>try</literal> (the default), <literal>on</literal>, - and <literal>off</literal>. + Controls whether huge pages are requested for the main shared memory + area. Valid values are <literal>try</literal> (the default), + <literal>on</literal>, and <literal>off</literal>. With + <varname>huge_pages</varname> set to <literal>try</literal>, the + server will try to request huge pages, but fall back to the default if + that fails. With <literal>on</literal>, failure to request huge pages + will prevent the server from starting up. With <literal>off</literal>, + huge pages will not be requested. </para> <para> - At present, this feature is supported only on Linux and Windows. The - setting is ignored on other systems when set to <literal>try</literal>. + At present, this setting is supported only on Linux and Windows. The + setting is ignored on other systems when set to + <literal>try</literal>. </para> <para> @@ -1401,11 +1407,18 @@ include_dir 'conf.d' </para> <para> - With <varname>huge_pages</varname> set to <literal>try</literal>, - the server will try to use huge pages, but fall back to using - normal allocation if that fails. With <literal>on</literal>, failure - to use huge pages will prevent the server from starting up. With - <literal>off</literal>, huge pages will not be used. + Note that this setting only affects the main shared memory area. + Operating systems such as Linux, FreeBSD, and Illumos can also use + huge pages (also known as <quote>super</quote> pages or + <quote>large</quote> pages) automatically for normal memory + allocation, without an explicit request from + <productname>PostgreSQL</productname>. On Linux, this is called + <quote>transparent huge pages</quote><indexterm><primary>transparent + huge pages</primary></indexterm> (THP). That feature has been known to + cause performance degradation with + <productname>PostgreSQL</productname> for some users on some Linux + versions, so its use is currently discouraged (unlike explicit use of + <varname>huge_pages</varname>). </para> </listitem> </varlistentry> |