Messages in this thread | | | Date | Thu, 04 Nov 2010 23:28:04 +0100 | From | Victor Jimenez <> | Subject | Re: perf tools miscellaneous questions |
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On 11/04/2010 09:58 PM, Francis Moreau wrote: > Francis Moreau<francis.moro@gmail.com> writes: > >> Francis Moreau<francis.moro@gmail.com> writes: >> > [...] > >>> 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: >>> >> oops sorry, I replied too early... >> >> so my cache configuration is: >> >> L1 -> L2 -> LLC >> >> where L2 misses is given by: 'cache-misses' - 'LLC-load-misses' >> >> Is that correct ? >> >> If so, I found 'cache-misses' term very not intuitive IMHO, probably >> because I'm not an expert in cpu caches... > Well thinking more about it, the above is wrong and I'm lost. > > If 'cache-misses' is the last level cache misses then how to interpret > these results ? > > $ perf stat -e llc-load-misses:u,llc-store-misses:u true > > Performance counter stats for 'true': > > 94 LLC-load-misses > 0 LLC-store-misses > > 0.000981840 seconds time elapsed > > > $ perf stat -e cache-misses:u true > > Performance counter stats for 'true': > > 796 cache-misses > > 0.001345136 seconds time elapsed > > Here 'cache-misses' value is much more than llc misses one... > If you are measuring last level cache misses, I would recommend you to use a memory intensive application/benchmark instead of /bin/true, as otherwise there can be a significant variation between two runs.
Victor
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Victor Jimenez Perez Barcelona Supercomputing Center Centro Nacional de Supercomputacion WWW: http://www.bsc.es e-mail: victor.javier@bsc.es
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