From: | Tatsuo Ishii <t-ishii(at)sra(dot)co(dot)jp> |
---|---|
To: | tgl(at)sss(dot)pgh(dot)pa(dot)us |
Cc: | yutaka(at)nonsensecorner(dot)com, xoror(at)infuse(dot)org, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: lru cache replacement |
Date: | 2003-06-24 14:59:34 |
Message-ID: | 20030624.235934.41643845.t-ishii@sra.co.jp |
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Lists: | pgsql-hackers |
> Yutaka tanida <yutaka(at)nonsensecorner(dot)com> writes:
> > xoror(at)infuse(dot)org wrote:
> >> does pgbench test with relatively large sequential scans?
>
> > Probably no.
>
> pgbench tries to avoid any seqscans at all, I believe, so it wouldn't be
> very useful for testing a method that's mainly intended to prevent
> seqscans from blowing out the cache.
>
> I tried to implement LRU-2 awhile ago, and got discouraged when I
> couldn't see any performance improvement. But I was using pgbench as
> the test case, and failed to think about its lack of seqscans.
>
> We could probably resurrect that code for comparison to 2Q, if anyone
> can devise more interesting benchmark cases to test.
>
> BTW, when you were running your test case, what shared_buffers did you
> use?
It's very easy to test sequencial scans using pgbench: just drop the
index from account table. I am using this technique to generate heavy
loads.
--
Tatsuo Ishii
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