Re: wal_buffers - Mailing list pgsql-hackers

From Robert Haas
Subject Re: wal_buffers
Date
Msg-id CA+TgmoYL6GsPdpBbjhfj8xeCLdXmFBZCW1s9ZGxDv+efj=E2dA@mail.gmail.com
Whole thread Raw
In response to Re: wal_buffers  (Euler Taveira de Oliveira <euler@timbira.com>)
Responses Re: wal_buffers  (Tom Lane <tgl@sss.pgh.pa.us>)
Re: wal_buffers  (Fujii Masao <masao.fujii@gmail.com>)
List pgsql-hackers
On Sun, Feb 19, 2012 at 9:46 AM, Euler Taveira de Oliveira
<euler@timbira.com> wrote:
> On 19-02-2012 02:24, Robert Haas wrote:
>> I have attached tps scatterplots.  The obvious conclusion appears to
>> be that, with only 16MB of wal_buffers, the buffer "wraps around" with
>> some regularity
>>
> Isn't it useful to print some messages on the log when we have "wrap around"?
> In this case, we have an idea that wal_buffers needs to be increased.

I was thinking about that.  I think that what might be more useful
than a log message is a counter somewhere in shared memory.  Logging
imposes a lot of overhead, which is exactly what we don't want here,
and the volume might be quite high on a system that is bumping up
against this problem.  Of course then the question is... how would we
expose the counter value?

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company


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