Re: Proposal of tunable fix for scalability of 8.4

[Scott Carey <scott@xxxxxxxxxxxxxxxxx>]

Title: Re: Proposal of tunable fix for scalability of 8.4

On 3/12/09 10:53 AM, "Tom Lane" <tgl@xxxxxxxxxxxxx> wrote:

> "Kevin Grittner" <Kevin.Grittner@xxxxxxxxxxxx> writes:
> > You misunderstood me.  I wasn't addressing the affects of his change,
> > but rather the fact that his test shows a linear improvement in TPS up
> > to 1000 connections for a 64 thread machine which is dealing entirely
> > with RAM -- no disk access.  Where's the bottleneck that allows this
> > to happen?  Without understanding that, his results are meaningless.
>
> Yeah, that is a really good point.  For a CPU-bound test you would
> ideally expect linear performance improvement up to the point at which
> number of active threads equals number of CPUs, and flat throughput
> with more threads.  The fact that his results don't look like that
> should excite deep suspicion that something is wrong somewhere.
>
> This does not in itself prove that the idea is wrong, but it does say
> that there is some major effect happening in this test that we don't
> understand.  Without understanding it, it's impossible to guess whether
> the proposal is helpful in any other scenario.
>
>                         regards, tom lane
Only on the assumption that each thread in the load test is running in ASAP mode rather than a metered pace.