linux-kernel - Re: perf tools miscellaneous questions

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Date:	Thu, 04 Nov 2010 09:34:04 +0100
From:	Francis Moreau <francis.moro@...il.com>
To:	Reid Kleckner <reid.kleckner@...il.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Stephane Eranian <eranian@...gle.com>,
	linux-perf-users@...r.kernel.org
Subject: Re: perf tools miscellaneous questions

Reid Kleckner <reid.kleckner@...il.com> writes:

> On Wed, Nov 3, 2010 at 5:43 PM, Frederic Weisbecker <fweisbec@...il.com> wrote:
>>> What's exactly the 'cache-misses' event ? does it include both instructions
>>> _and_ data cache misses ? both L1 and L2 caches ?
>>>
>
>>> I was expecting so but the following command makes me wondering:
>>>
>>>   $ perf stat -e cache-misses:u,l1d-loads-misses:u true
>>>     Performance counter stats for 'true':
>>>
>>>                 763  cache-misses
>>>                 874  L1-dcache-load-misses
>>>
>>>         0.000916609  seconds time elapsed
>>>
>>> Here cache-misses < L1-dcache-load-misses.
>>
>>
>>
>> Dunno, will let others answer.
>
> I think it corresponds to last level cache misses, which makes sense
> here.  The difference in the two numbers represents hits to L2 (and L3
> if it exists).

How could I know the number of cache level on my cpu ?

I tried:

  $ perf stat -e cache-misses:u,l1d-loads-misses:u true

    Performance counter stats for 'true':

                   802  cache-misses
                   937  L1-dcache-load-misses

           0.000996578  seconds time elapsed

  $ perf stat -e cache-misses:u,L2-loads-misses:u true

   Performance counter stats for 'true':

                  788  cache-misses
                   95  LLC-load-misses

          0.001025423  seconds time elapsed

So it looks like you're right: in my case I have this cache
configuration:










--
Francis
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