Re: [PATCH 0/4] pending scheduler updates

From: Mike Galbraith
Date: Wed Oct 22 2008 - 09:05:53 EST

On Wed, 2008-10-22 at 14:42 +0200, Ingo Molnar wrote:
> * Mike Galbraith <efault@xxxxxx> wrote:
> > > > With that patch, pgsql+oltp scales perfectly.
> > >
> > > hm, tempting.
> >
> > I disagree. Postgres's scaling problem is trivially corrected by
> > twiddling knobs (or whatnot). [...]
> okay, then we need to document it a bit more: what knobs need twiddling
> to make it scale perfectly?

Twiddle sched_wakeup_granularity_ns or just turn FAIR_SLEEPERS off for
best pgsql+oltp scalability.ï Pgsql+oltp collapse is delicate. It
doesn't take much to send it one way or the other. Cut preempt a wee
bit, and it can snap right into shape.

I think we need to penalize sleepers a wee bit as load climbs in general
though, everybody begins to like preemption less as load increases.
Mysql+oltp improves as well, and it loves preempt at modest load.


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