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author | Michael Paquier <michael@paquier.xyz> | 2021-04-22 09:47:43 +0900 |
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committer | Michael Paquier <michael@paquier.xyz> | 2021-04-22 09:47:43 +0900 |
commit | 1599e7b375127cac81b539d2c69d3faf7598509b (patch) | |
tree | 00d56eac4c3b1405d12f55c3763e9167aeb85917 | |
parent | 7c298c6573a0f181963ddcb40c850fa9c7da0ada (diff) | |
download | postgresql-1599e7b375127cac81b539d2c69d3faf7598509b.tar.gz postgresql-1599e7b375127cac81b539d2c69d3faf7598509b.zip |
doc: Move parallel_leader_participation to its correct category
parallel_leader_participation got introduced in e5253fd, where it was
listed under RESOURCES_ASYNCHRONOUS in guc.c, but the documentation
did not reflect that and listed it with the other planner-related
options. This commit fixes this inconsistency as the parameter is
intended to be an asynchronous one.
While on it, reorganize a bit the section dedicated to asynchronous
parameters, backend_flush_after being moved first to do better in terms
of alphabetical order of the options listed.
Reported-by: Yanliang Lei
Author: Bharath Rupireddy
Discussion: https://postgr.es/m/16972-42d4b0c15aa1d5f5@postgresql.org
-rw-r--r-- | doc/src/sgml/config.sgml | 88 |
1 files changed, 44 insertions, 44 deletions
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index dd7ebe7a9da..cf75d913ce9 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -2383,6 +2383,36 @@ include_dir 'conf.d' <title>Asynchronous Behavior</title> <variablelist> + <varlistentry id="guc-backend-flush-after" xreflabel="backend_flush_after"> + <term><varname>backend_flush_after</varname> (<type>integer</type>) + <indexterm> + <primary><varname>backend_flush_after</varname> configuration parameter</primary> + </indexterm> + </term> + <listitem> + <para> + Whenever more than this amount of data has + been written by a single backend, attempt to force the OS to issue + these writes to the underlying storage. Doing so will limit the + amount of dirty data in the kernel's page cache, reducing the + likelihood of stalls when an <function>fsync</function> is issued at the end of a + checkpoint, or when the OS writes data back in larger batches in the + background. Often that will result in greatly reduced transaction + latency, but there also are some cases, especially with workloads + that are bigger than <xref linkend="guc-shared-buffers"/>, but smaller + than the OS's page cache, where performance might degrade. This + setting may have no effect on some platforms. + If this value is specified without units, it is taken as blocks, + that is <symbol>BLCKSZ</symbol> bytes, typically 8kB. + The valid range is + between <literal>0</literal>, which disables forced writeback, + and <literal>2MB</literal>. The default is <literal>0</literal>, i.e., no + forced writeback. (If <symbol>BLCKSZ</symbol> is not 8kB, + the maximum value scales proportionally to it.) + </para> + </listitem> + </varlistentry> + <varlistentry id="guc-effective-io-concurrency" xreflabel="effective_io_concurrency"> <term><varname>effective_io_concurrency</varname> (<type>integer</type>) <indexterm> @@ -2579,32 +2609,25 @@ include_dir 'conf.d' </listitem> </varlistentry> - <varlistentry id="guc-backend-flush-after" xreflabel="backend_flush_after"> - <term><varname>backend_flush_after</varname> (<type>integer</type>) + <varlistentry id="guc-parallel-leader-participation" xreflabel="parallel_leader_participation"> + <term> + <varname>parallel_leader_participation</varname> (<type>boolean</type>) <indexterm> - <primary><varname>backend_flush_after</varname> configuration parameter</primary> + <primary><varname>parallel_leader_participation</varname> configuration parameter</primary> </indexterm> </term> <listitem> <para> - Whenever more than this amount of data has - been written by a single backend, attempt to force the OS to issue - these writes to the underlying storage. Doing so will limit the - amount of dirty data in the kernel's page cache, reducing the - likelihood of stalls when an <function>fsync</function> is issued at the end of a - checkpoint, or when the OS writes data back in larger batches in the - background. Often that will result in greatly reduced transaction - latency, but there also are some cases, especially with workloads - that are bigger than <xref linkend="guc-shared-buffers"/>, but smaller - than the OS's page cache, where performance might degrade. This - setting may have no effect on some platforms. - If this value is specified without units, it is taken as blocks, - that is <symbol>BLCKSZ</symbol> bytes, typically 8kB. - The valid range is - between <literal>0</literal>, which disables forced writeback, - and <literal>2MB</literal>. The default is <literal>0</literal>, i.e., no - forced writeback. (If <symbol>BLCKSZ</symbol> is not 8kB, - the maximum value scales proportionally to it.) + Allows the leader process to execute the query plan under + <literal>Gather</literal> and <literal>Gather Merge</literal> nodes + instead of waiting for worker processes. The default is + <literal>on</literal>. Setting this value to <literal>off</literal> + reduces the likelihood that workers will become blocked because the + leader is not reading tuples fast enough, but requires the leader + process to wait for worker processes to start up before the first + tuples can be produced. The degree to which the leader can help or + hinder performance depends on the plan type, number of workers and + query duration. </para> </listitem> </varlistentry> @@ -5889,29 +5912,6 @@ SELECT * FROM parent WHERE key = 2400; </listitem> </varlistentry> - <varlistentry id="guc-parallel-leader-participation" xreflabel="parallel_leader_participation"> - <term> - <varname>parallel_leader_participation</varname> (<type>boolean</type>) - <indexterm> - <primary><varname>parallel_leader_participation</varname> configuration parameter</primary> - </indexterm> - </term> - <listitem> - <para> - Allows the leader process to execute the query plan under - <literal>Gather</literal> and <literal>Gather Merge</literal> nodes - instead of waiting for worker processes. The default is - <literal>on</literal>. Setting this value to <literal>off</literal> - reduces the likelihood that workers will become blocked because the - leader is not reading tuples fast enough, but requires the leader - process to wait for worker processes to start up before the first - tuples can be produced. The degree to which the leader can help or - hinder performance depends on the plan type, number of workers and - query duration. - </para> - </listitem> - </varlistentry> - <varlistentry id="guc-plan-cache_mode" xreflabel="plan_cache_mode"> <term><varname>plan_cache_mode</varname> (<type>enum</type>) <indexterm> |