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SubjectRe: [PATCH] perf_events: add sampling period randomization support (v2)
On 02.03.10 16:21:45, eranian@google.com 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.
>
> Randomization is activated by setting perf_event_attr.random_period_width
> to a non-zero value. It represents the width of the mask to apply to the
> random value, i.e, maximum range of variation. The random value is applied
> AROUND the period, i.e., period may be longer or shorter with a maximum
> variation of half the bit width. Thus, on average the sampling period remains
> equal to the initial period passed in perf_event_attr.sample_period.
>
> 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.
>
> Randomization is implemented in generic code thus it applies to all
> PMU models and software events.
>
> Signed-off-by: Stephane Eranian <eranian@google.com>
>
> --
> include/linux/perf_event.h | 3 +++
> kernel/perf_event.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 47 insertions(+)

Reviewed-by: Robert Richter <robert.richter@amd.com>

--
Advanced Micro Devices, Inc.
Operating System Research Center
email: robert.richter@amd.com



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