RE: v7.1b4 bad performance

> -----Original Message-----
> From: Tom Lane [mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us]
> Sent: Friday, February 16, 2001 7:13 PM
> To: Schmidt, Peter
> Cc: 'Bruce Momjian'; 'Michael Ansley'; 'pgsql-admin(at)postgresql(dot)org'
> Subject: Re: [ADMIN] v7.1b4 bad performance
>
>
> "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
>

I get ~50 tps for any commit_delay value > 0. I've tried many values in the
range 0 - 999, and always get ~50 tps. commit_delay=0 always gets me ~200+
tps.

Yes, I have tried multiple clients but got stuck on the glaring difference
between versions with a single client. The tests that I ran showed the same
kind of results you got earlier today i.e. 1 client/1000 transactions = 10
clients/100 transactions.

So, is it OK to use commit_delay=0?

Peter