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From: Mehmet B. <mb...@gm...> - 2008-03-07 18:50:25
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Calibrator results sound about right to me. Are you looking at a manual for a newer architecture? Because those data sheet values are way too small for old architectures (if only they were correct !!!). For recent architectures, I would believe these values might be correct tough. Just for fun: here's (http://people.cs.vt.edu/~mehmetb/drop/Estimation.pdf) how close I got to estimating performance using HW counter stats. On a second look, I did pretty good :-) X axis is different problem sizes (matrices). Y is the time per problem. The red curve is the baseline. Than I did some optimizations and measured the results (blue curve) and I estimated the expected performance improvements (black curve) by using cache event stats (nothing fancy: time_def = num_event * event_latency). I will appreciate all comments/suggestions... -Memo On Fri, Mar 7, 2008 at 5:58 AM, Andi Kleen <an...@fi...> wrote: > "Mehmet Belgin" <mb...@gm...> writes: > > > (Calibrator estimates for an Athlon machine) > > Assuming you mean a K8, but K7 is similar > > > L1 latency : 12 cycles > > It should be <= 4 cycles actually. > > > L2 latency : 162 cycles > > That looks far too slow. Normally it should be <20 cycles > (minimum 13 cycles) according to data sheets. > > Looks to me like calibrator is not very accurate. > > -Andi > |