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Subject: Re: load balancing regression since commit 367456c7
From: Tim Chen <tim.c.chen@linux.intel.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>, Alex Shi <alex.shi@intel.com>,
        Ying <ying.huang@intel.com>,
        linux-kernel <linux-kernel@vger.kernel.org>
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Date: Fri, 20 Apr 2012 09:40:42 -0700
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On Fri, 2012-04-20 at 16:00 +0200, Peter Zijlstra wrote:

> 
> Ok, so I can't reproduce this on my WSM-EP.. even !PREEMPT kernels are
> consistent with hackbench times with or without that patch.
> 
> Can you still send your full .config? Also, do you have cpu-cgroup muck
> enabled and are you using that systemd shite?
> 
> What does the below patch (on top of the previous) do?
> 

There is a slight 10% to 15% improvement with the patch.  However,
the change in performance difficult to quantify precisely as the 
hackbench runtime has large variations (up to 50%) on our Sandy Bridge EP
server machines since commit 367456c7.

We also do not see regression for hackbench on WSM-EP, but only 
on machines with Sandy-Bridge EP (2 socket, 8 cores/socket, HT enabled).  
We are not running hackbench in cgroup for this test.

The Sandy Bridge EP machines installed has FC16, so I think it uses 
systemd. The machine on our WSM EP has FC15, which also has systemd.

I'm sending you the .config in a separate mail.  Thanks for taking a look.
The .config aligns closely with standard Fedora settings.

Tim