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doc: Improve calculation of vm.nr_hugepages

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The previous method worked off the full virtual address space, not just
the shared memory usage.

Author: Tsunakawa, Takayuki <tsunakawa.takay@jp.fujitsu.com>
Reviewed-by: Justin Pryzby <pryzby@telsasoft.com>
Reviewed-by: Vasundhar Boddapati <bvasundhar@gmail.com>
This commit is contained in:
Peter Eisentraut 2018-03-06 21:45:28 -05:00
parent 0c2c81b403
commit a3739e376f
1 changed files with 3 additions and 3 deletions
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doc/src/sgml/runtime.sgml
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@ -1472,14 +1472,14 @@ export PG_OOM_ADJUST_VALUE=0
the kernel setting <varname>vm.nr_hugepages</varname>. To estimate the
number of huge pages needed, start <productname>PostgreSQL</productname>
without huge pages enabled and check the
postmaster's <varname>VmPeak</varname> value, as well as the system's
postmaster's anonymous shared memory segment size, as well as the system's
huge page size, using the <filename>/proc</filename> file system. This might
look like:
<programlisting>
$ <userinput>head -1 $PGDATA/postmaster.pid</userinput>
4170
$ <userinput>grep ^VmPeak /proc/4170/status</userinput>
VmPeak: 6490428 kB
$ <userinput>pmap 4170 | awk '/rw-s/ &amp;&amp; /zero/ {print $2}'</userinput>
6490428K
$ <userinput>grep ^Hugepagesize /proc/meminfo</userinput>
Hugepagesize: 2048 kB
</programlisting>