Messages in this thread | | | Date | Thu, 29 Nov 2012 15:19:16 +0530 | From | Raghavendra K T <> | Subject | Re: [PATCH V3 RFC 0/2] kvm: Improving undercommit scenarios |
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On 11/29/2012 07:37 AM, Chegu Vinod wrote: > On 11/26/2012 4:07 AM, Raghavendra K T wrote: >> In some special scenarios like #vcpu <= #pcpu, PLE handler may >> prove very costly, because there is no need to iterate over vcpus >> and do unsuccessful yield_to burning CPU. >> >> The first patch optimizes all the yield_to by bailing out when there >> is no need to continue in yield_to (i.e., when there is only one task >> in source and target rq). >> >> Second patch uses that in PLE handler. Further when a yield_to fails >> we do not immediately go out of PLE handler instead we try thrice >> to have better statistical possibility of false return. Otherwise that >> would affect moderate overcommit cases. >> Result on 3.7.0-rc6 kernel shows around 140% improvement for ebizzy >> 1x and >> around 51% for dbench 1x with 32 core PLE machine with 32 vcpu guest. >> >> >> base = 3.7.0-rc6 >> machine: 32 core mx3850 x5 PLE mc >> >> --+-----------+-----------+-----------+------------+-----------+ >> ebizzy (rec/sec higher is beter) >> --+-----------+-----------+-----------+------------+-----------+ >> base stdev patched stdev %improve >> --+-----------+-----------+-----------+------------+-----------+ >> 1x 2511.3000 21.5409 6051.8000 170.2592 140.98276 >> 2x 2679.4000 332.4482 2692.3000 251.4005 0.48145 >> 3x 2253.5000 266.4243 2192.1667 178.9753 -2.72169 >> 4x 1784.3750 102.2699 2018.7500 187.5723 13.13485 >> --+-----------+-----------+-----------+------------+-----------+ >> >> --+-----------+-----------+-----------+------------+-----------+ >> dbench (throughput in MB/sec. higher is better) >> --+-----------+-----------+-----------+------------+-----------+ >> base stdev patched stdev %improve >> --+-----------+-----------+-----------+------------+-----------+ >> 1x 6677.4080 638.5048 10098.0060 3449.7026 51.22643 >> 2x 2012.6760 64.7642 2019.0440 62.6702 0.31639 >> 3x 1302.0783 40.8336 1292.7517 27.0515 -0.71629 >> 4x 3043.1725 3243.7281 4664.4662 5946.5741 53.27643 >> --+-----------+-----------+-----------+------------+-----------+ >> >> Here is the refernce of no ple result. >> ebizzy-1x_nople 7592.6000 rec/sec >> dbench_1x_nople 7853.6960 MB/sec >> >> The result says we can still improve by 60% for ebizzy, but overall we >> are >> getting impressive performance with the patches. >> >> Changes Since V2: >> - Dropped global measures usage patch (Peter Zilstra) >> - Do not bail out on first failure (Avi Kivity) >> - Try thrice for the failure of yield_to to get statistically more >> correct >> behaviour. >> >> Changes since V1: >> - Discard the idea of exporting nrrunning and optimize in core >> scheduler (Peter) >> - Use yield() instead of schedule in overcommit scenarios (Rik) >> - Use loadavg knowledge to detect undercommit/overcommit >> >> Peter Zijlstra (1): >> Bail out of yield_to when source and target runqueue has one task >> >> Raghavendra K T (1): >> Handle yield_to failure return for potential undercommit case >> >> Please let me know your comments and suggestions. >> >> Link for V2: >> https://lkml.org/lkml/2012/10/29/287 >> >> Link for V1: >> https://lkml.org/lkml/2012/9/21/168 >> >> kernel/sched/core.c | 25 +++++++++++++++++++------ >> virt/kvm/kvm_main.c | 26 ++++++++++++++++---------- >> 2 files changed, 35 insertions(+), 16 deletions(-) >> >> . >> > Tested-by: Chegu Vinod <chegu_vinod@hp.com> >
Thanks for testing..
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