Messages in this thread | | | Date | Thu, 4 Mar 2010 09:52:56 +0100 | From | Robert Richter <> | Subject | Re: [PATCH] perf_events: add sampling period randomization support (v2) |
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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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