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Re: [HACKERS] 8.3beta1 testing on Solaris

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Jignesh K(dot) Shah" <J(dot)K(dot)Shah(at)Sun(dot)COM>
Cc: Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-performance(at)postgresql(dot)org, Gregory Stark <stark(at)enterprisedb(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: [HACKERS] 8.3beta1 testing on Solaris
Date: 2007-10-26 19:08:16
Message-ID: 24692.1193425696@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-performance
"Jignesh K. Shah" <J(dot)K(dot)Shah(at)Sun(dot)COM> writes:
> So the ratio of reads vs writes to clog files is pretty huge..

It looks to me that the issue is simply one of not having quite enough
CLOG buffers.  Your first run shows 8 different pages being fetched and
the second shows 10.  Bearing in mind that we "pin" the latest CLOG page
into buffers, there are only NUM_CLOG_BUFFERS-1 buffers available for
older pages, so what we've got here is thrashing for the available
slots.

Try increasing NUM_CLOG_BUFFERS to 16 and see how it affects this test.

			regards, tom lane

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