Re: [PATCH 0/4] pending scheduler updates

From: Mike Galbraith
Date: Wed Oct 22 2008 - 06:32:24 EST

On Wed, 2008-10-22 at 12:03 +0200, Mike Galbraith wrote:

> It has positive effects too, but IMHO, the bad outweigh the good.

BTW, most dramatic on the other end of the spectrum is pgsql+oltp. With
preemption as is, it collapses as load climbs to heavy with preemption
knobs at stock. Postgres uses user-land spinlocks and _appears_ to wake
others while these are still held. For this load, there is such a thing
as too much short-term fairness, preempting lock holder creates nasty
gaggle of contended lock spinners. It's curable with knobs, and I think
it's postgres's own fault, but may be wrong.

With that patch, pgsql+oltp scales perfectly.


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