Messages in this thread | | | Date | Fri, 6 Jul 2007 17:03:51 -0400 | From | Mathieu Desnoyers <> | Subject | Re: [patch 10/10] Scheduler profiling - Use immediate values |
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* Li, Tong N (tong.n.li@intel.com) wrote: > > I found that memory latency is difficult to measure in modern x86 > > CPUs because they have very clever prefetchers that can often > > outwit benchmarks. > > A pointer-chasing program that accesses a random sequence of addresses > usually can produce a good estimate on memory latency. Also, prefetching > can be turned off in BIOS or by modifying the MSRs. > > > Another trap on P4 is that RDTSC is actually quite slow and > synchronizes > > the CPU; that can add large measurement errors. > > > > -Andi > > The cost can be amortized if the portion of memory accesses is long > enough. > > tong >
That's what I am currently doing.. the results are coming in a few moments... :)
-- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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