On Tue, Jan 22, 2013 at 01:08:54PM +0530, 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 > --+-----------+-----------+-----------+------------+-----------+ > > --+-----------+-----------+-----------+------------+-----------+ > 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 > --+-----------+-----------+-----------+------------+-----------+ > > 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 the discussion of V3 original: > https://lkml.org/lkml/2012/11/26/166 > > 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(-) Applied, thanks. -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
