| From: | "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> |
|---|---|
| To: | "Robert Haas" <robertmhaas(at)gmail(dot)com>, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | "Greg Smith" <gsmith(at)gregsmith(dot)com>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org>, "Scott Carey" <scott(at)richrelevance(dot)com>, "Jignesh K(dot) Shah" <J(dot)K(dot)Shah(at)sun(dot)com> |
| Subject: | Re: Proposal of tunable fix for scalability of 8.4 |
| Date: | 2009-03-13 18:02:24 |
| Message-ID: | 49BA5960.EE98.0025.0@wicourts.gov |
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| Lists: | pgsql-performance |
Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> I think that changing the locking behavior is attacking the problem
>> at the wrong level anyway.
>
> Right. By the time a patch here could have any effect, you've
> already lost the game --- having to deschedule and reschedule a
> process is a large cost compared to the typical lock hold time for
> most LWLocks. So it would be better to look at how to avoid
> blocking in the first place.
That's what motivated my request for a profile of the "80 clients with
zero wait" case. If all data access is in RAM, why can't 80 processes
keep 64 threads (on 8 processors) busy? Does anybody else think
that's an interesting question, or am I off in left field here?
-Kevin
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