| From: | "Christopher Kings-Lynne" <chriskl(at)familyhealth(dot)com(dot)au> |
|---|---|
| To: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | "Hackers" <pgsql-hackers(at)postgresql(dot)org>, <pgsql-performance(at)postgresql(dot)org>, "Advocacy" <pgsql-advocacy(at)postgresql(dot)org> |
| Subject: | Re: [HACKERS] More benchmarking of wal_buffers |
| Date: | 2003-02-14 03:04:20 |
| Message-ID: | GNELIHDDFBOCMGBFGEFOOEIOCFAA.chriskl@familyhealth.com.au |
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| Thread: | |
| Lists: | pgsql-advocacy pgsql-hackers pgsql-performance |
> I don't think this is based on a useful test for wal_buffers. The
> wal_buffers setting only has to be large enough for the maximum amount
> of WAL log data that your system emits between commits, because a commit
> (from anyone) is going to flush the WAL data to disk (for everyone).
> So a benchmark based on short transactions is just not going to show
> any benefit to increasing the setting.
Yes, I guess the TPC-B test does many, very short transactions. Each
transaction bascially comprises a single update, so I guess it wouldn't
really test it.
> > One proof that has come out of this is that wal_buffers does not affect
> > SELECT only performance in any way.
>
> Coulda told you that without testing ;-). Read-only transactions emit
> no WAL entries.
I knew that as well, that's why I said "proof" ;)
Chris
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