On Thu, 10 Aug 2017 09:18:09 -0400 Eric Farman <farman@xxxxxxxxxxxxxxxxxx> wrote: > On 08/08/2017 04:14 AM, Longpeng (Mike) wrote: > > > > > > On 2017/8/8 15:41, Cornelia Huck wrote: > > > >> On Tue, 8 Aug 2017 12:05:31 +0800 > >> "Longpeng(Mike)" <longpeng2@xxxxxxxxxx> wrote: > >> > >>> This is a simple optimization for kvm_vcpu_on_spin, the > >>> main idea is described in patch-1's commit msg. > >> > >> I think this generally looks good now. > >> > >>> > >>> I did some tests base on the RFC version, the result shows > >>> that it can improves the performance slightly. > >> > >> Did you re-run tests on this version? > > > > > > Hi Cornelia, > > > > I didn't re-run tests on V2. But the major difference between RFC and V2 > > is that V2 only cache result for X86 (s390/arm needn't) and V2 saves a > > expensive operation ( 440-1400 cycles on my test machine ) for X86/VMX. > > > > So I think V2's performance is at least the same as RFC or even slightly > > better. :) > > > >> > >> I would also like to see some s390 numbers; unfortunately I only have a > >> z/VM environment and any performance numbers would be nearly useless > >> there. Maybe somebody within IBM with a better setup can run a quick > >> test? > > Won't swear I didn't screw something up, but here's some quick numbers. > Host was 4.12.0 with and without this series, running QEMU 2.10.0-rc0. > Created 4 guests, each with 4 CPU (unpinned) and 4GB RAM. VM1 did full > kernel compiles with kernbench, which took averages of 5 runs of > different job sizes (I threw away the "-j 1" numbers). VM2-VM4 ran cpu > burners on 2 of their 4 cpus. > > Numbers from VM1 kernbench output, and the delta between runs: > > load -j 3 before after delta > Elapsed Time 183.178 182.58 -0.598 > User Time 534.19 531.52 -2.67 > System Time 32.538 33.37 0.832 > Percent CPU 308.8 309 0.2 > Context Switches 98484.6 99001 516.4 > Sleeps 227347 228752 1405 > > load -j 16 before after delta > Elapsed Time 153.352 147.59 -5.762 > User Time 545.829 533.41 -12.419 > System Time 34.289 34.85 0.561 > Percent CPU 347.6 348 0.4 > Context Switches 160518 159120 -1398 > Sleeps 240740 240536 -204 Thanks a lot, Eric! The decreases in elapsed time look nice, and we probably should not care about the increases reported.
