| From: | Fujii Masao <masao(dot)fujii(at)gmail(dot)com> |
|---|---|
| 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: | 2011-01-17 01:15:46 |
| Message-ID: | AANLkTi=Dgn-3jRj+QUMCunMgicwifZENHXKnKMuTQWA5@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Sun, Jan 16, 2011 at 7:34 AM, 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.
If the workload generates 16MB or more WAL for wal_writer_delay,
16MB or more of wal_buffers would be effective. In that case,
wal_buffers is likely to be filled up with unwritten WAL, then you have
to write buffers while holding WALInsert lock. This is obviously not
good.
Regards,
--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center
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