Re: Comparing postgresql7.4 CVS head on linux 2.4.20 and 2.6.0-test4

On 27 Aug 2003 at 19:00, Neil Conway wrote:

> On Wed, Aug 27, 2003 at 09:02:25PM +0530, Shridhar Daithankar wrote:
> > IIRC in a kernel release note recently, it was commented that IO scheduler is
> > still being worked on and does not perform as much for random seeks, which
> > exaclty what database needs.
>
> Yeah, I've read that as well. It would be interesting to see how 2.6
> performs with the traditional (non-anticipatory) scheduler -- I believe
> you can switch from one I/O scheduler to another via a sysctl.

I will repeat the tests after get that setting. Will google for it..

>
> > pgbench -c10 -t100 test1
> > tps = 64.917044 (including connections establishing)
> > tps = 65.438067 (excluding connections establishing)
>
> Interesting that the performance of 2.4.20 for this particular
> benchmark is a little less than 3 times faster than 2.6

Yeah but 2.4 drops like anything..
> > 4) noatime enabled Shared buffers 3000
> >
> > pgbench -c5 -t100 test
> > tps = 90.850600 (including connections establishing)
> > tps = 92.053686 (excluding connections establishing)
> >
> > pgbench -c5 -t1000 test
> > tps = 92.209724 (including connections establishing)
> > tps = 92.329682 (excluding connections establishing)
> >
> > pgbench -c10 -t100 test
> > tps = 79.264231 (including connections establishing)
> > tps = 80.145448 (excluding connections establishing)
>
> I'm a little skeptical of the consistency of these numbers
> (several people have observed in the past that it's difficult
> to get pgbench to produce reliable results) -- how is it
> possible that using noatime can possibly *reduce* performance
> by 50%, in the case of the first and third benchmarks?

I know. I am puzzled too. Probably I didn't put noatime properly in /etc/fstab.
Unfortunately I have only one linux partition. So I prefer to boot rather than
remounting root.

I will redo the bechmarks and post the results..

Bye
Shridhar

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