Dave,
Ok, I missed that, I am sorry.
I will add this to the patch with a small modification given
that perf_randomize_event_period() modifies last_period.
Thus it needs to be after the assignment to data.period.
Thanks.
On Tue, Mar 2, 2010 at 7:20 AM, David Miller <da...@davemloft.net> wrote:
> From: eran...@google.com
> Date: Mon, 1 Mar 2010 22:07:09 -0800
>
> > 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.
> >
> > Signed-off-by: Stephane Eranian <eran...@google.com>
>
> Please add this, which adds the feature to sparc too.
>
> diff --git a/arch/sparc/kernel/perf_event.c
> b/arch/sparc/kernel/perf_event.c
> index 9f2b2ba..3e28225 100644
> --- a/arch/sparc/kernel/perf_event.c
> +++ b/arch/sparc/kernel/perf_event.c
> @@ -1214,6 +1214,9 @@ static int __kprobes perf_event_nmi_handler(struct
> notifier_block *self,
> if (val & (1ULL << 31))
> continue;
>
> + if (event->attr.random)
> + perf_randomize_event_period(event);
> +
> data.period = event->hw.last_period;
> if (!sparc_perf_event_set_period(event, hwc, idx))
> continue;
>
--
Stephane Eranian | EMEA Software Engineering
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