Re: [PATCH 0/5] perf: add support for capturing skid IP

From	Stephane Eranian <eranian@google.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 0/5] perf: add support for capturing skid IP
Date	2017-06-16 09:00 +0200
Message-ID	<tSToB-4Ym-5@gated-at.bofh.it> (permalink)
References	(4 earlier) <tSIMy-6Ci-7@gated-at.bofh.it> <tSJfz-726-5@gated-at.bofh.it> <tSJyV-78N-3@gated-at.bofh.it> <tSLr4-8li-17@gated-at.bofh.it> <tSMdr-qd-9@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

Andi,

On Thu, Jun 15, 2017 at 4:18 PM, Andi Kleen <ak@linux.intel.com> wrote:
>> Looking at this approach, the user interface is straightforward,
>> implementation in the x86 code is a bit more hairy because of the way
>> the branch_stack is captured, via the cpuc->lbr_entries. If you assume
>> that SKID_IP cannot be used with any other branch stack mode, then it
>> is easy. It becomes messy if you don't.
>
> That should be fine. After all if you have real LBRs you don't need
> the skid IP.
>
Yes, you still do. This is not the same thing. LBR captures only taken branches.
I care about taken AND non-taken branches and I don't want to sample on a
non-taken event, assuming it is available.

You need to inject the skid ip into the LBR stack somehow. Either
directly in the
registers or in the cpuc->lbr_entries. The injection can only happen
on interrupt
whereas the LBR captures 32 branches. So you'd have the skid ip info
only for the
most recent branch in the stack.

Thread

[PATCH 0/5] perf: add support for capturing skid IP Stephane Eranian <eranian@google.com> - 2017-06-15 16:00 +0200
  [PATCH 2/5] perf/x86: add PERF_SAMPLE_SKID_IP support for X86 PEBS Stephane Eranian <eranian@google.com> - 2017-06-15 16:00 +0200
    RE: [PATCH 2/5] perf/x86: add PERF_SAMPLE_SKID_IP support for X86  PEBS "Liang, Kan" <kan.liang@intel.com> - 2017-06-15 17:50 +0200
      Re: [PATCH 2/5] perf/x86: add PERF_SAMPLE_SKID_IP support for X86 PEBS Stephane Eranian <eranian@google.com> - 2017-06-15 18:40 +0200
        RE: [PATCH 2/5] perf/x86: add PERF_SAMPLE_SKID_IP support for X86  PEBS "Liang, Kan" <kan.liang@intel.com> - 2017-06-15 19:20 +0200
        Re: [PATCH 2/5] perf/x86: add PERF_SAMPLE_SKID_IP support for X86 PEBS Stephane Eranian <eranian@google.com> - 2017-06-15 21:20 +0200
  [PATCH 3/5] perf/tools: add support for PERF_SAMPLE_SKID_IP Stephane Eranian <eranian@google.com> - 2017-06-15 16:00 +0200
  [PATCH 4/5] perf/record: add support for sampling skid ip Stephane Eranian <eranian@google.com> - 2017-06-15 16:00 +0200
  Re: [PATCH 0/5] perf: add support for capturing skid IP Andi Kleen <ak@linux.intel.com> - 2017-06-15 17:20 +0200
    Re: [PATCH 0/5] perf: add support for capturing skid IP Stephane Eranian <eranian@google.com> - 2017-06-15 18:50 +0200
      Re: [PATCH 0/5] perf: add support for capturing skid IP Andi Kleen <ak@linux.intel.com> - 2017-06-15 19:30 +0200
        Re: [PATCH 0/5] perf: add support for capturing skid IP Stephane Eranian <eranian@google.com> - 2017-06-15 21:40 +0200
          Re: [PATCH 0/5] perf: add support for capturing skid IP Andi Kleen <ak@linux.intel.com> - 2017-06-15 22:10 +0200
            Re: [PATCH 0/5] perf: add support for capturing skid IP Stephane Eranian <eranian@google.com> - 2017-06-15 22:30 +0200
              Re: [PATCH 0/5] perf: add support for capturing skid IP Stephane Eranian <eranian@google.com> - 2017-06-16 00:30 +0200
                Re: [PATCH 0/5] perf: add support for capturing skid IP Andi Kleen <ak@linux.intel.com> - 2017-06-16 01:20 +0200
                Re: [PATCH 0/5] perf: add support for capturing skid IP Stephane Eranian <eranian@google.com> - 2017-06-16 09:00 +0200
                Re: [PATCH 0/5] perf: add support for capturing skid IP Andi Kleen <ak@linux.intel.com> - 2017-06-16 18:10 +0200
                Re: [PATCH 0/5] perf: add support for capturing skid IP Stephane Eranian <eranian@google.com> - 2017-06-16 19:10 +0200
                Re: [PATCH 0/5] perf: add support for capturing skid IP Stephane Eranian <eranian@google.com> - 2017-06-16 19:20 +0200
                Re: [PATCH 0/5] perf: add support for capturing skid IP Andi Kleen <ak@linux.intel.com> - 2017-06-16 20:00 +0200
                Re: [PATCH 0/5] perf: add support for capturing skid IP Stephane Eranian <eranian@google.com> - 2017-06-16 21:20 +0200

csiph-web