| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> |
| Cc: | "Heikki Linnakangas" <heikki(dot)linnakangas(at)enterprisedb(dot)com>, "Simon Riggs" <simon(at)2ndquadrant(dot)com>, "Andrew Dunstan" <andrew(at)dunslane(dot)net>, "Robert Haas" <robertmhaas(at)gmail(dot)com>, "Greg Smith" <gsmith(at)gregsmith(dot)com>, "Stefan Kaltenbrunner" <stefan(at)kaltenbrunner(dot)cc>, "PostgreSQL-development" <pgsql-hackers(at)postgresql(dot)org>, "Alan Li" <ali(at)truviso(dot)com> |
| Subject: | Re: 8.4 open item: copy performance regression? |
| Date: | 2009-06-22 20:28:37 |
| Message-ID: | 556.1245702517@sss.pgh.pa.us |
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"Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> writes:
> Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> I wonder though whether the wal_buffers setting interacts with the
>> ring size. Has everyone who's tested this used the same 16MB
>> wal_buffers setting as in Alan's original scenario?
> I had been using his postgresql.conf file, then added autovacuum =
> off. When I tried with setting the ring size to 16MB, I accidentally
> left off the step to copy the postgresql.conf file, and got better
> performance.
Huh, that's bizarre. I can see that increasing shared_buffers should
make no difference in this test case (we're not using them all anyway).
But why should increasing wal_buffers make it slower? I forget the
walwriter's control algorithm at the moment ... maybe it works harder
when wal buffers are full?
BTW, I committed the change to use 16MB; that will be in RC2.
regards, tom lane
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