| From: | Marti Raudsepp <marti(at)juffo(dot)org> |
|---|---|
| To: | Josh Berkus <josh(at)agliodbs(dot)com> |
| Cc: | Greg Smith <greg(at)2ndquadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, Magnus Hagander <magnus(at)hagander(dot)net>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: auto-sizing wal_buffers |
| Date: | 2011-01-16 22:46:06 |
| Message-ID: | AANLkTinCtnctB-OuqEg_dv=JBcpJFvzyvWuf83qHfGEa@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Sun, Jan 16, 2011 at 00:34, Josh Berkus <josh(at)agliodbs(dot)com> wrote:
> I think we can be more specific on that last sentence; is there even any
> *theoretical* benefit to settings above 16MB, the size of a WAL segment?
> Certainly there have been no test results to show any.
I don't know if it's applicable to real workloads in any way, but it
did make a measurable difference in one of my tests.
Back when benchmarking different wal_sync_methods, I found that when
doing massive INSERTs from generate_series, the INSERT time kept
improving even after increasing wal_buffers from 16MB to 32, 64 and
128MB; especially with wal_sync_method=open_datasync. The total
INSERT+COMMIT time remained constant, however.
More details here:
http://archives.postgresql.org/pgsql-performance/2010-11/msg00094.php
Regards,
Marti
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