Messages in this thread | | | Date | Fri, 2 Jul 2004 00:04:48 +0200 | From | bert hubert <> | Subject | perfctr questions |
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Mikael,
I'm trying to test your performance counters stuff, but I can't get it to do anything remotely useful! Probably just me.
I have a very hard time understanding things like:
* perfex -e 0x00039000/0x04000204@0x8000000C some_program * * Explanation: Program IQ_CCCR0 with required flags, ESCR select 4 * (== CRU_ESCR0), and Enable. Program CRU_ESCR0 with event 2 * (instr_retired), NBOGUSNTAG, CPL>0. Map this event to IQ_COUNTER0 * (0xC) with fast RDPMC enabled.
I'd love to author a small perfctr howto for people like me who just want to know if their code is thrashing the cache.
Do you have a pointer to tools that do this, or, how to calculate these 0x00039000 numbers for perfex? I can't find anything relevant. The best information I found is in the 'hardmeter' sources.
I tried one very basic thing, perfex -e 0x00410005 ./null which I hoped would measure unaligned memory accesses, but I can't get this counter raised from 0. null.c:
int main(int argc, char **argv) { char room[12]; int i, n;
for(n=0;n<1000000;++n) { i=*((int*)(room+n%4)); } printf("%d\n", i); }
I'm on a Pentium M, 2.6.7-mm5. Not even sure if an Pentium M will measure cache misses though.
Thanks
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