linux-kernel - Re: PostgreSQL pgbench performance regression in 2.6.23+

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Message-ID: <20080522082814.GA4499@linux.vnet.ibm.com>
Date:	Thu, 22 May 2008 13:58:14 +0530
From:	Dhaval Giani <dhaval@...ux.vnet.ibm.com>
To:	Mike Galbraith <efault@....de>
Cc:	Greg Smith <gsmith@...gsmith.com>,
	lkml <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>
Subject: Re: PostgreSQL pgbench performance regression in 2.6.23+

On Thu, May 22, 2008 at 09:10:07AM +0200, Mike Galbraith wrote:
> 
> On Wed, 2008-05-21 at 13:34 -0400, Greg Smith wrote:
> > PostgreSQL ships with a simple database benchmarking tool named pgbench, 
> > in what's labeled the contrib section (in many distributions it's a 
> > separate package from the main server/client ones).  I see there's been 
> > some work done already improving how the PostgreSQL server works under the 
> > new scheduler (the "Poor PostgreSQL scaling on Linux 2.6.25-rc5" thread). 
> > I wanted to provide you a different test case using pgbench that has taken 
> > a sharp dive starting with 2.6.23, and the server improvement changes in 
> > 2.6.25 actually made this problem worse.
> > 
> > I think it will be easy for someone else to replicate my results and I'll 
> > go over the exact procedure below.
> 
> Yup, I can reproduce.  Running the test with 2.6.25.4, everything is
> waking/running on one CPU, leaving my box 75% idle.  Not good.
> 

Can you try with 2.6.26-rc? There is minimal load balancing for group
scheduling till 25, which might explain the lack of scalability.

-- 
regards,
Dhaval
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