linux-kernel - Re: [PATCH 1/6] perf, x86: Making hardware events tranlations sysfs available

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Message-ID: <CABPqkBT4GPTp3k6Ko-t4Q5Kgz54O5yBZ7L+9M6Uc660rxTtrAA@mail.gmail.com>
Date:	Fri, 15 Jun 2012 09:32:20 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>, acme@...hat.com,
	mingo@...e.hu, paulus@...ba.org, cjashfor@...ux.vnet.ibm.com,
	fweisbec@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6] perf, x86: Making hardware events tranlations sysfs available

On Fri, Jun 15, 2012 at 9:29 AM, Jiri Olsa <jolsa@...hat.com> wrote:
> On Thu, Jun 14, 2012 at 11:36:51PM +0200, Stephane Eranian wrote:
>> On Thu, Jun 14, 2012 at 11:09 PM, Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:
>> > On Thu, 2012-06-14 at 22:38 +0200, Jiri Olsa wrote:
>> >> Making hardware events tranlations available throught the sysfs.
>> >> Adding 'events' group attribute under the sysfs x86 PMU record
>> >> with attribute/file for each hardware event:
>> >>
>> >>   # ls  /sys/devices/cpu/events/
>> >>   branch_instructions
>> >>   branch_misses
>> >>   bus_cycles
>> >>   cache_misses
>> >>   cache_references
>> >>   cycles
>> >>   instructions
>> >>   ref_cycles
>> >>   stalled_cycles_backend
>> >>   stalled_cycles_frontend
>> >>
>> >> The file - ID mappings is:
>> >>
>> >>   file                      hw id
>> >>   ----------------------------------------------------------------
>> >>   cycles                    PERF_COUNT_HW_CPU_CYCLES
>> >>   instructions              PERF_COUNT_HW_INSTRUCTIONS
>> >>   cache_references          PERF_COUNT_HW_CACHE_REFERENCES
>> >>   cache_misses              PERF_COUNT_HW_CACHE_MISSES
>> >>   branch_instructions       PERF_COUNT_HW_BRANCH_INSTRUCTIONS
>> >>   branch_misses             PERF_COUNT_HW_BRANCH_MISSES
>> >>   bus_cycles                PERF_COUNT_HW_BUS_CYCLES
>> >>   stalled_cycles_frontend   PERF_COUNT_HW_STALLED_CYCLES_FRONTEND
>> >>   stalled_cycles_backend    PERF_COUNT_HW_STALLED_CYCLES_BACKEND
>> >>   ref_cycles                PERF_COUNT_HW_REF_CPU_CYCLES
>> >>
>> >> Each attribute/file contains HW ID event translation for the currently
>> >> running CPU model
>> >>
>> >>   # cat /sys/devices/cpu/events/instructions
>> >>   0xc0
>> >
>> > Why not have it consistent with the stuff done for uncore where events
>> > read: 'event=0xc0', ie the regular field=value stuff.
>> >
>> Yes, you want that. Because those events may need more than a code.
>> You want full syntax capability. So return a string.
>
> humm... right :)
>
> how about the term name 'event=...', could I always assume it's 'event',
> or do we want some arch specific connection for that?
>
You should not assume anything. You grab the string from sysfs and put it
through your regular parser. It could have arch specific terms in it. That's
how I suspect this is done for uncore.

> jirka
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