Re: [PATCH RFC V8 0/17] Paravirtualized ticket spinlocks
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On 05/07/2012 08:22 PM, Avi Kivity wrote: I could not come with pv-flush results (also Nikunj had clarified that the result was on NOn PLE
I'd like to see those numbers, then. Ingo, please hold on the kvm-specific patches, meanwhile.
3 guests 8GB RAM, 1 used for kernbench (kernbench -f -H -M -o 20) other for cpuhog (shell script with while true do hackbench) 1x: no hogs 2x: 8hogs in one guest 3x: 8hogs each in two guest kernbench on PLE:Machine : IBM xSeries with Intel(R) Xeon(R) X7560 2.27GHz CPU with 32 core, with 8 online cpus and 4*64GB RAM.
The average is taken over 4 iterations with 3 run each (4*3=12). and stdev is calculated over mean reported in each run.
A): 8 vcpu guestBASE BASE+patch %improvement w.r.t mean (sd) mean (sd) patched kernel time
case 1*1x: 61.7075 (1.17872) 60.93 (1.475625) 1.27605 case 1*2x: 107.2125 (1.3821349) 97.506675 (1.3461878) 9.95401 case 1*3x: 144.3515 (1.8203927) 138.9525 (0.58309319) 3.8855 B): 16 vcpu guestBASE BASE+patch %improvement w.r.t mean (sd) mean (sd) patched kernel time
case 2*1x: 70.524 (1.5941395) 69.68866 (1.9392529) 1.19867 case 2*2x: 133.0738 (1.4558653) 124.8568 (1.4544986) 6.58114 case 2*3x: 206.0094 (1.3437359) 181.4712 (2.9134116) 13.5218 B): 32 vcpu guestBASE BASE+patch %improvementw.r.t mean (sd) mean (sd) patched kernel time
case 4*1x: 100.61046 (2.7603485) 85.48734 (2.6035035) 17.6905 It seems while we do not see any improvement in low contention case, the benefit becomes evident with overcommit and large guests. I am continuing analysis with other benchmarks (now with pgbench to check if it has acceptable improvement/degradation in low contenstion case). Avi, Can patch series go ahead for inclusion into tree with following reasons: The patch series brings fairness with ticketlock ( hence the predictability, since during contention, vcpu tryingto acqire lock is sure that it gets its turn in less than total number of vcpus conntending for lock), which is very much desired irrespective
of its low benefit/degradation (if any) in low contention scenarios. Ofcourse ticketlocks had undesirable effect of exploding LHP problem,and the series addresses with improvement in scheduling and sleeping instead of burning cpu time.
Finally a less famous one, it brings almost PLE equivalent capabilty toall the non PLE hardware (TBH I always preferred my experiment kernel to be compiled in my pv guest that saves more than 30 min of time for each run).
It would be nice to see any results if somebody got benefited/suffered with patchset.
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