diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/config.sgml | 41 |
1 files changed, 32 insertions, 9 deletions
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index de84b777300..a09ceb2fea7 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -2344,15 +2344,38 @@ include_dir 'conf.d' </indexterm> </term> <listitem> - <para> - Specifies the delay between activity rounds for the WAL writer. - In each round the writer will flush WAL to disk. It then sleeps for - <varname>wal_writer_delay</> milliseconds, and repeats. The default - value is 200 milliseconds (<literal>200ms</>). Note that on many - systems, the effective resolution of sleep delays is 10 milliseconds; - setting <varname>wal_writer_delay</> to a value that is not a multiple - of 10 might have the same results as setting it to the next higher - multiple of 10. This parameter can only be set in the + <para> + Specifies how often the WAL writer flushes WAL. After flushing WAL it + sleeps for <varname>wal_writer_delay</> milliseconds, unless woken up + by an asynchronously committing transaction. In case the last flush + happened less than <varname>wal_writer_delay</> milliseconds ago and + less than <varname>wal_writer_flush_after</> bytes of WAL have been + produced since, WAL is only written to the OS, not flushed to disk. + The default value is 200 milliseconds (<literal>200ms</>). Note that + on many systems, the effective resolution of sleep delays is 10 + milliseconds; setting <varname>wal_writer_delay</> to a value that is + not a multiple of 10 might have the same results as setting it to the + next higher multiple of 10. This parameter can only be set in the + <filename>postgresql.conf</> file or on the server command line. + </para> + </listitem> + </varlistentry> + + <varlistentry id="guc-wal-writer-flush-after" xreflabel="wal_writer_flush_after"> + <term><varname>wal_writer_flush_after</varname> (<type>integer</type>) + <indexterm> + <primary><varname>wal_writer_flush_after</> configuration parameter</primary> + </indexterm> + </term> + <listitem> + <para> + Specifies how often the WAL writer flushes WAL. In case the last flush + happened less than <varname>wal_writer_delay</> milliseconds ago and + less than <varname>wal_writer_flush_after</> bytes of WAL have been + produced since, WAL is only written to the OS, not flushed to disk. + If <varname>wal_writer_flush_after</> is set to <literal>0</> WAL is + flushed everytime the WAL writer has written WAL. The default is + <literal>1MB</literal>. This parameter can only be set in the <filename>postgresql.conf</> file or on the server command line. </para> </listitem> |