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Date: Tue, 5 Jul 2011 10:50:32 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Hu Tao <hutao@cn.fujitsu.com>
Cc: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>, Paul Turner <pjt@google.com>,
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        Pavel Emelyanov <xemul@openvz.org>
Subject: Re: [patch 00/16] CFS Bandwidth Control v7
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* Hu Tao <hutao@cn.fujitsu.com> wrote:

> perf diff output:
> 
> # Baseline  Delta          Shared Object                       Symbol
> # ........ ..........  .................  ...........................
> #
>      0.00%    +10.07%  [kernel.kallsyms]  [k] __lock_acquire
>      0.00%     +5.90%  [kernel.kallsyms]  [k] lock_release
>      0.00%     +4.86%  [kernel.kallsyms]  [k] trace_hardirqs_off_caller
>      0.00%     +4.06%  [kernel.kallsyms]  [k] debug_smp_processor_id
>      0.00%     +4.00%  [kernel.kallsyms]  [k] lock_acquire
>      0.00%     +3.81%  [kernel.kallsyms]  [k] lock_acquired
>      0.00%     +3.71%  [kernel.kallsyms]  [k] lock_is_held
>      0.00%     +3.04%  [kernel.kallsyms]  [k] validate_chain
>      0.00%     +2.68%  [kernel.kallsyms]  [k] check_chain_key
>      0.00%     +2.41%  [kernel.kallsyms]  [k] trace_hardirqs_off
>      0.00%     +2.01%  [kernel.kallsyms]  [k] trace_hardirqs_on_caller

Oh, please measure with lockdep (CONFIG_PROVE_LOCKING) turned off. No 
production kernel has it enabled and it has quite some overhead (as 
visible in the profile), skewing results.

>      2.04%     -0.09%  pipe-test-100k     [.] main
>      0.00%     +1.79%  [kernel.kallsyms]  [k] add_preempt_count

I'd also suggest to turn off CONFIG_PREEMPT_DEBUG.

Thanks,

	Ingo