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Subject: Re: [PATCH] perf_events: add sampling period randomization support
From: Peter Zijlstra <peterz@infradead.org>
To: Robert Richter <robert.richter@amd.com>
Cc: eranian@google.com, linux-kernel@vger.kernel.org, mingo@elte.hu,
       paulus@samba.org, fweisbec@gmail.com, perfmon2-devel@lists.sf.net,
       eranian@gmail.com
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Date: Tue, 02 Mar 2010 12:41:18 +0100
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On Tue, 2010-03-02 at 11:53 +0100, Robert Richter wrote:
> 
> Only adding the random value will lead to longer sample periods on
> average. To compensate this you could calculate something like:
> 
>          event->hw.sample_period = event->attr.sample_period + (new_seed & mask) - (mask >> 1);

Or cheat and do something like:

  sample_period ^= (new_seed & mask);