On 06/16/2011 08:20 AM, Avi Kivity wrote: > On 06/16/2011 05:19 PM, David Ahern wrote: >> On 06/16/2011 08:08 AM, David Ahern wrote: >> > Command: >> > perf stat -e instructions openssl speed aes >> >> Hmm.. this might be the wrong benchmark for this. I thought >> openssl-speed was a purely CPU intensive benchmark which should have >> fairly similar performance numbers in both host and guest. I seem to >> recall this as true 2 or so years ago, but that is not the case with >> 3.0-rc2 and F14. >> >> Using a benchmark Vince W. wrote seems better: >> http://www.csl.cornell.edu/~vince/projects/perf_counter/million.s >> >> perf stat -e instructions ./million >> >> Performance counter stats for './million': >> >> 1,113,650 instructions # 0.00 insns per cycle >> > > Maybe it's sensitive to a cpuid bit which we don't pass through - likely > a bug in qemu or perhaps in kvm. > Seems to be a side effect of running perf-stat in the guest. Running just 'openssl speed aes' in both host and guest shows very similar numbers (for the first 3 columns). Adding the 'perf stat' to the command (ie., perf stat openssl speed aes) causes a significant decline in the guest - by a factor of 2. For comparison 'perf stat' in the host has a negligible impact. David -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
