On 2017/8/10 21:18, Eric Farman 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 Eric! The `Elapsed Time` is smaller with this series , the result is the same as my numbers in cover-letter. > > - Eric > > > . > -- Regards, Longpeng(Mike)
