Re: [PATCH] perf_events: add sampling period randomization support

From: Peter Zijlstra
Date: Tue Mar 02 2010 - 04:13:58 EST

On Mon, 2010-03-01 at 22:07 -0800, eranian@xxxxxxxxxx wrote:
> This patch adds support for randomizing the sampling period.
> Randomization is very useful to mitigate the bias that exists
> with sampling. The random number generator does not need to
> be sophisticated. This patch uses the builtin random32()
> generator.
> The user activates randomization by setting the perf_event_attr.random
> field to 1 and by passing a bitmask to control the range of variation
> above the base period. Period will vary from period to period & mask.
> Note that randomization is not available when a target interrupt rate
> (freq) is enabled.
> The last used period can be collected using the PERF_SAMPLE_PERIOD flag
> in sample_type.
> The patch has been tested on X86. There is also code for PowerPC but
> I could not test it.

I don't thikn we need to touch the arch code, we didn't need to for
frequency driven sampling, so I don't see a reason to do so for
randomization either.

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