Messages in this thread | | | Subject | Re: [PATCH v2 0/4] KVM: optimize the kvm_vcpu_on_spin | From | Eric Farman <> | Date | Thu, 10 Aug 2017 09:18:09 -0400 |
| |
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@huawei.com> 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
- Eric
| |