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Re: [RFC PATCH 0/6] perf: Add AUX data sampling

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On Fri, Sep 23, 2016 at 01:49:17PM +0200, Peter Zijlstra wrote:
> On Fri, Sep 23, 2016 at 02:27:20PM +0300, Alexander Shishkin wrote:
> > Hi Peter,
> > 
> > This is an RFC, I'm not sending the tooling bits in this series,
> > although they can be found here [1].
> > 
> > This series introduces AUX data sampling for perf events, which in
> > case of our instruction/branch tracing PMUs like Intel PT, BTS, CS
> > ETM means execution flow history leading up to a perf event's
> > overflow.
> 
> This fails to explain _WHY_ this is a good thing to have. What kind of
> analysis does this enable, and is that fully implemented in [1] (I
> didn't look).

Think of it as a super LBR. (Near) all things LBR can do, PT can do
with much more branches for each sample.

Also long term execution recording of PT normally doesn't work well because the
sustained bandwidth is too high for perf and the disk to keep up

Currently the main solution we have for that is the snapshot mode, but it
requires explicit instrumentation for someone to trigger snapshots.

Sampling PT is an alternative that works for many use cases, and does
not rely on instrumentation.

-Andi

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[RFC PATCH 0/6] perf: Add AUX data sampling Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2016-09-23 13:30 +0200
  [RFC PATCH 1/6] perf: Move mlock accounting to ring buffer allocation Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2016-09-23 13:30 +0200
    Re: [RFC PATCH 1/6] perf: Move mlock accounting to ring buffer  allocation Peter Zijlstra <peterz@infradead.org> - 2016-09-23 14:20 +0200
      Re: [RFC PATCH 1/6] perf: Move mlock accounting to ring buffer allocation Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2016-09-23 16:40 +0200
        Re: [RFC PATCH 1/6] perf: Move mlock accounting to ring buffer  allocation Peter Zijlstra <peterz@infradead.org> - 2016-09-23 17:30 +0200
          Re: [RFC PATCH 1/6] perf: Move mlock accounting to ring buffer allocation Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2016-09-23 18:00 +0200
      Re: [RFC PATCH 1/6] perf: Move mlock accounting to ring buffer  allocation Andi Kleen <ak@linux.intel.com> - 2016-09-23 19:30 +0200
        Re: [RFC PATCH 1/6] perf: Move mlock accounting to ring buffer  allocation Peter Zijlstra <peterz@infradead.org> - 2016-09-23 22:30 +0200
          Re: [RFC PATCH 1/6] perf: Move mlock accounting to ring buffer allocation Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2016-09-26 10:30 +0200
            Re: [RFC PATCH 1/6] perf: Move mlock accounting to ring buffer  allocation Peter Zijlstra <peterz@infradead.org> - 2016-09-26 11:10 +0200
              Re: [RFC PATCH 1/6] perf: Move mlock accounting to ring buffer allocation Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2016-09-26 14:50 +0200
              Re: [RFC PATCH 1/6] perf: Move mlock accounting to ring buffer allocation Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2016-09-26 18:20 +0200
  [RFC PATCH 2/6] perf: Add api to (de-)allocate AUX buffers for kernel counters Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2016-09-23 13:40 +0200
  [RFC PATCH 3/6] perf: Add a helper for looking up pmus by type Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2016-09-23 13:40 +0200
  [RFC PATCH 4/6] perf: Add infrastructure for using AUX data in perf samples Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2016-09-23 13:40 +0200
  [RFC PATCH 5/6] perf: Disable PMU around address filter adjustment Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2016-09-23 13:40 +0200
  [RFC PATCH 6/6] perf: Disable IRQs in address filter sync path Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2016-09-23 13:40 +0200
    Re: [RFC PATCH 6/6] perf: Disable IRQs in address filter sync path Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2016-09-26 18:30 +0200
      Re: [RFC PATCH 6/6] perf: Disable IRQs in address filter sync path Mathieu Poirier <mathieu.poirier@linaro.org> - 2016-10-04 18:50 +0200
  Re: [RFC PATCH 0/6] perf: Add AUX data sampling Peter Zijlstra <peterz@infradead.org> - 2016-09-23 13:50 +0200
    Re: [RFC PATCH 0/6] perf: Add AUX data sampling Andi Kleen <ak@linux.intel.com> - 2016-09-23 19:20 +0200
      Re: [RFC PATCH 0/6] perf: Add AUX data sampling Peter Zijlstra <peterz@infradead.org> - 2016-09-23 22:40 +0200
        Re: [RFC PATCH 0/6] perf: Add AUX data sampling Andi Kleen <ak@linux.intel.com> - 2016-09-24 00:40 +0200

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