| From: | Jeff Davis <pgsql(at)j-davis(dot)com> |
|---|---|
| To: | Hannu Krosing <hannu(at)skype(dot)net> |
| Cc: | Luke Lonergan <LLonergan(at)greenplum(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Grzegorz Jaskiewicz <gj(at)pointblue(dot)com(dot)pl>, PGSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Doug Rady <drady(at)greenplum(dot)com>, Sherry Moore <sherry(dot)moore(at)sun(dot)com> |
| Subject: | Re: Bug: Buffer cache is not scan resistant |
| Date: | 2007-03-05 20:12:34 |
| Message-ID: | 1173125554.13722.318.camel@dogma.v10.wvs |
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| Lists: | pgsql-hackers |
On Mon, 2007-03-05 at 11:10 +0200, Hannu Krosing wrote:
> > My proposal for a fix: ensure that when relations larger (much larger?)
> > than buffer cache are scanned, they are mapped to a single page in the
> > shared buffer cache.
>
> How will this approach play together with synchronized scan patches ?
>
Thanks for considering my patch in this discussion. I will test by
turning shared_buffers down as low as I can, and see if that makes a big
difference.
> Or should synchronized scan rely on systems cache only ?
>
I don't know what the performance impact of that will be; still good
compared to reading from disk, but I assume much more CPU time.
Regards,
Jeff Davis
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