Re: why does swap not recover? - Mailing list pgsql-performance

From Josh Berkus
Subject Re: why does swap not recover?
Date
Msg-id 4BB197B3.3050306@agliodbs.com
Whole thread Raw
In response to why does swap not recover?  (Richard Yen <dba@richyen.com>)
List pgsql-performance
On 3/26/10 4:57 PM, Richard Yen wrote:
> I'm planning on lowering the shared_buffers to a more sane value, like 25GB (pgtune recommends this for a
Mixed-purposemachine) or less (pgtune recommends 14GB for an OLTP machine).  However, before I do this (and possibly
resolvethe issue), I was hoping to see if anyone would have an explanation for the constant reading from swap, but
neverwriting back. 

Postgres does not control how swap is used.  This would be an operating
system issue.  Leaving aside the distict possibility of a bug in
handling swap (nobody seems to do it well), there's the distinct
possibility that you're actually pinning more memory on the system than
it has (through various processes) and it's wisely shifted some
read-only files to the swap (as opposed to read-write ones).  But that's
a fairly handwavy guess.

--
                                  -- Josh Berkus
                                     PostgreSQL Experts Inc.
                                     http://www.pgexperts.com

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