Re: [RFC PATCH 0/3]perf/core: extend perf_reg and perf_sample_regs_intr

From	Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Newsgroups	linux.kernel
Subject	Re: [RFC PATCH 0/3]perf/core: extend perf_reg and perf_sample_regs_intr
Date	2015-11-07 05:40 +0100
Message-ID	<qs3se-5TG-3@gated-at.bofh.it> (permalink)
References	(1 earlier) <qrssF-78k-3@gated-at.bofh.it> <qrJDc-1sw-9@gated-at.bofh.it> <qrLvk-2Eh-25@gated-at.bofh.it> <qrM81-36S-9@gated-at.bofh.it> <qrMro-3f3-13@gated-at.bofh.it>
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On Friday 06 November 2015 03:55 PM, Peter Zijlstra wrote:
> On Fri, Nov 06, 2015 at 09:04:00PM +1100, Michael Ellerman wrote:
>> It's a perrenial request from our hardware PMU folks to be able to see the raw
>> values of the PMU registers.
>>
>> I think partly it's so that they can verify that perf is doing what they want,
>> and some of it is that they're interested in some of the more obscure info that
>> isn't plumbed out through other perf interfaces.
>>
>> We've used various internal hacks over the years to keep them happy. This is an
>> attempt to use a somewhat standard mechanism.
>>
>> It would also be helpful for those of us working on the perf hardware backends,
>> to be able to verify that we're programming things correctly, without resorting
>> to debug printks etc.
>>
>> Basically we want to sample regs at the time of the perf interrupt, so we
>> though PERF_SAMPLE_REGS_INTR made senes :)
>>
>> But if you think this is the wrong mechanism within perf, then please let us
>> know.
>>
>> I know perf's mission is to abstract as much of the arcane hardware details
>> into a generic interface and make PMUs actually useful for normal folks, and we
>> are committed to that, but it would also be useful to be able to get the raw
>> values for a different type of user.
>>
>> Maddy's patch only exports PMC1-6 and MMCR0/1. I think we also need to export
>> some others, in particular MMCRA has a lot of stuff in it, half of which is not
>> even architected. So that would have to be exported as "POWER8_MMCRA". And then
>> there's the SIAR/SDAR/SIER which contain a bunch of info on sampled
>> instructions that is not currently plumbed out.
> OK, no objections then. But this is useful information and should be
> included in the patch set.
>

Sure. Will add the information in the next version.

Maddy


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Thread

[RFC PATCH  0/3]perf/core: extend perf_reg and perf_sample_regs_intr Madhavan Srinivasan <maddy@linux.vnet.ibm.com> - 2015-11-04 21:50 +0100
  [RFC PATCH  1/3] perf/core: extend perf_regs to include arch specific regs Madhavan Srinivasan <maddy@linux.vnet.ibm.com> - 2015-11-04 21:50 +0100
  [RFC PATCH  3/3]perf/powerpc: Functions to update arch_misc_regs Madhavan Srinivasan <maddy@linux.vnet.ibm.com> - 2015-11-04 21:50 +0100
  [RFC PATCH  2/3]perf/powerpc: update macros and add regs to arch_misc_reg struct Madhavan Srinivasan <maddy@linux.vnet.ibm.com> - 2015-11-04 21:50 +0100
  Re: [RFC PATCH  0/3]perf/core: extend perf_reg and  perf_sample_regs_intr Peter Zijlstra <peterz@infradead.org> - 2015-11-05 14:10 +0100
    Re: [RFC PATCH  0/3]perf/core: extend perf_reg and  perf_sample_regs_intr Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> - 2015-11-06 04:10 +0100
      Re: [RFC PATCH 0/3]perf/core: extend perf_reg and  perf_sample_regs_intr Madhavan Srinivasan <maddy@linux.vnet.ibm.com> - 2015-11-06 08:50 +0100
        Re: [RFC PATCH 0/3]perf/core: extend perf_reg and  perf_sample_regs_intr Michael Ellerman <mpe@ellerman.id.au> - 2015-11-06 10:50 +0100
    Re: [RFC PATCH 0/3]perf/core: extend perf_reg and  perf_sample_regs_intr Madhavan Srinivasan <maddy@linux.vnet.ibm.com> - 2015-11-06 08:30 +0100
      Re: [RFC PATCH 0/3]perf/core: extend perf_reg and  perf_sample_regs_intr Peter Zijlstra <peterz@infradead.org> - 2015-11-06 10:30 +0100
        Re: [RFC PATCH 0/3]perf/core: extend perf_reg and  perf_sample_regs_intr Michael Ellerman <mpe@ellerman.id.au> - 2015-11-06 11:10 +0100
          Re: [RFC PATCH 0/3]perf/core: extend perf_reg and  perf_sample_regs_intr Peter Zijlstra <peterz@infradead.org> - 2015-11-06 11:30 +0100
            Re: [RFC PATCH 0/3]perf/core: extend perf_reg and  perf_sample_regs_intr Madhavan Srinivasan <maddy@linux.vnet.ibm.com> - 2015-11-07 05:40 +0100
            Re: [RFC PATCH 0/3]perf/core: extend perf_reg and  perf_sample_regs_intr Michael Ellerman <mpe@ellerman.id.au> - 2015-11-10 01:30 +0100
          Re: [RFC PATCH 0/3]perf/core: extend perf_reg and  perf_sample_regs_intr Madhavan Srinivasan <maddy@linux.vnet.ibm.com> - 2015-11-07 05:30 +0100
  Re: [RFC PATCH 0/3]perf/core: extend perf_reg and perf_sample_regs_intr Stephane Eranian <eranian@googlemail.com> - 2015-11-05 15:50 +0100
    Re: [RFC PATCH 0/3]perf/core: extend perf_reg and  perf_sample_regs_intr Madhavan Srinivasan <maddy@linux.vnet.ibm.com> - 2015-11-06 08:40 +0100

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