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

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Date:	Thu, 22 May 2008 12:34:25 +0200
From:	Mike Galbraith <efault@....de>
To:	Dhaval Giani <dhaval@...ux.vnet.ibm.com>
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, 2008-05-22 at 11:05 +0200, Mike Galbraith wrote:
> On Thu, 2008-05-22 at 13:58 +0530, Dhaval Giani wrote:

> > 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.
> 
> I'm playing with it now, it's tweakable with migration cost.  This
> testcase is funky.  It can't generate enough work to keep CPUs busy for
> spit, and can't saturate my little quad with any kernel I've tried.

Heh, watch this.  No tweaking.  

(Nadia's ipc/idr patches are applied though, to see if the high end
improves over previous runs with various kernels, and it does seem to.)

2.6.26-smp x86_64
1 10014.774797
2 9791.395302
3 10575.369296
4 9763.183251
5 10160.274262
6 9893.174179
8 9566.978464
10 10294.456456
15 9444.100540
20 9137.878618
30 8277.795499
40 7925.824428
50 7646.644285

nail postgres to CPUs1-3
nail pgbench to CPU0

2.6.26-smp x86_64
1 10900.959982
2 15976.870604
3 24661.322669
4 25347.141780
5 25893.815676
6 26756.414839
8 25399.018582
10 26172.878669
15 25542.082746
20 25090.381828
30 24270.301103
40 23405.867336
50 21926.223083



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