Re: perf tools miscellaneous questions
From: Francis Moreau
Date: Thu Nov 04 2010 - 04:34:55 EST
Reid Kleckner <reid.kleckner@xxxxxxxxx> writes:
> On Wed, Nov 3, 2010 at 5:43 PM, Frederic Weisbecker <fweisbec@xxxxxxxxx> 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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