Re: 20% performance drop on PostgreSQL 9.2 from kernel 3.5.3 to3.6-rc5 on AMD chipsets - bisected

From: Mike Galbraith
Date: Sat Sep 15 2012 - 00:12:02 EST

On Fri, 2012-09-14 at 23:27 +0200, Borislav Petkov wrote:
> (Adding everybody to CC and leaving the below for reference.)
> Guys,
> as Nikolay says below, we have a regression in 3.6 with pgbench's
> benchmark in postgresql.
> I was able to reproduce it on another box here and did a bisection run.
> It pointed to the commit below.
> And yes, reverting that commit fixes the issue here.

My wild (and only) theory is that this is userspace spinlock related.
If so, starting the server and benchmark SCHED_BATCH should not only
kill the regression, but likely improve throughput as well.


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