| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "Schmidt, Peter" <peter(dot)schmidt(at)prismedia(dot)com> |
| Cc: | "'Bruce Momjian'" <pgman(at)candle(dot)pha(dot)pa(dot)us>, "'Michael Ansley'" <Michael(dot)Ansley(at)intec-telecom-systems(dot)com>, "'pgsql-admin(at)postgresql(dot)org'" <pgsql-admin(at)postgresql(dot)org> |
| Subject: | Re: v7.1b4 bad performance |
| Date: | 2001-02-17 03:13:24 |
| Message-ID: | 23798.982379604@sss.pgh.pa.us |
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| Lists: | pgsql-admin |
"Schmidt, Peter" <peter(dot)schmidt(at)prismedia(dot)com> writes:
> I tried -B 1024 and got roughly the same results (~50 tps).
What were you using before?
> However, when I change WAL option commit_delay from the default of 5
> to 0, I get ~200 tps (which is double what I get with 7.03). I'm not
> sure I want to do this, do I?
Hmm. There have been several discussions about whether CommitDelay is
a good idea or not. What happens if you vary it --- try 1 microsecond,
and then various multiples of 1000. I suspect you may find that there
is no difference in the range 1..10000, then a step, then no change up
to 20000. In other words, your kernel may be rounding the delay up to
the next multiple of a clock tick, which might be 10 milliseconds.
That would explain a 50-tps limit real well...
BTW, have you tried pgbench with multiple clients (-c) rather than just
one?
regards, tom lane
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