diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/pgbuffercache.sgml | 85 |
1 files changed, 84 insertions, 1 deletions
diff --git a/doc/src/sgml/pgbuffercache.sgml b/doc/src/sgml/pgbuffercache.sgml index 802a5112d77..b5050cd7343 100644 --- a/doc/src/sgml/pgbuffercache.sgml +++ b/doc/src/sgml/pgbuffercache.sgml @@ -30,7 +30,9 @@ <para> This module provides the <function>pg_buffercache_pages()</function> function (wrapped in the <structname>pg_buffercache</structname> view), - the <function>pg_buffercache_summary()</function> function, the + <function>pg_buffercache_numa_pages()</function> function (wrapped in the + <structname>pg_buffercache_numa</structname> view), the + <function>pg_buffercache_summary()</function> function, the <function>pg_buffercache_usage_counts()</function> function and the <function>pg_buffercache_evict()</function> function. </para> @@ -43,6 +45,15 @@ </para> <para> + The <function>pg_buffercache_numa_pages()</function> provides + <acronym>NUMA</acronym> node mappings for shared buffer entries. This + information is not part of <function>pg_buffercache_pages()</function> + itself, as it is much slower to retrieve. + The <structname>pg_buffercache_numa</structname> view wraps the function for + convenient use. + </para> + + <para> The <function>pg_buffercache_summary()</function> function returns a single row summarizing the state of the shared buffer cache. </para> @@ -200,6 +211,78 @@ </para> </sect2> + <sect2 id="pgbuffercache-pg-buffercache-numa"> + <title>The <structname>pg_buffercache_numa</structname> View</title> + + <para> + The definitions of the columns exposed by the view are shown in <xref linkend="pgbuffercache-numa-columns"/>. + </para> + + <table id="pgbuffercache-numa-columns"> + <title><structname>pg_buffercache_numa</structname> Columns</title> + <tgroup cols="1"> + <thead> + <row> + <entry role="catalog_table_entry"><para role="column_definition"> + Column Type + </para> + <para> + Description + </para></entry> + </row> + </thead> + + <tbody> + <row> + <entry role="catalog_table_entry"><para role="column_definition"> + <structfield>bufferid</structfield> <type>integer</type> + </para> + <para> + ID, in the range 1..<varname>shared_buffers</varname> + </para></entry> + </row> + + <row> + <entry role="catalog_table_entry"><para role="column_definition"> + <structfield>os_page_num</structfield> <type>int</type> + </para> + <para> + number of OS memory page for this buffer + </para></entry> + </row> + + <row> + <entry role="catalog_table_entry"><para role="column_definition"> + <structfield>numa_node</structfield> <type>int</type> + </para> + <para> + ID of <acronym>NUMA</acronym> node + </para></entry> + </row> + + </tbody> + </tgroup> + </table> + + <para> + As <acronym>NUMA</acronym> node ID inquiry for each page requires memory pages + to be paged-in, the first execution of this function can take a noticeable + amount of time. In all the cases (first execution or not), retrieving this + information is costly and querying the view at a high frequency is not recommended. + </para> + + <warning> + <para> + When determining the <acronym>NUMA</acronym> node, the view touches + all memory pages for the shared memory segment. This will force + allocation of the shared memory, if it wasn't allocated already, + and the memory may get allocated in a single <acronym>NUMA</acronym> + node (depending on system configuration). + </para> + </warning> + + </sect2> + <sect2 id="pgbuffercache-summary"> <title>The <function>pg_buffercache_summary()</function> Function</title> |