On Mon, Mar 04, 2013 at 11:31:46PM +0530, Raghavendra K T wrote: > This patch series further filters better vcpu candidate to yield to > in PLE handler. The main idea is to record the preempted vcpus using > preempt notifiers and iterate only those preempted vcpus in the > handler. Note that the vcpus which were in spinloop during pause loop > exit are already filtered. > > Thanks Jiannan, Avi for bringing the idea and Gleb, PeterZ for > precious suggestions during the discussion. > Thanks Srikar for suggesting to avoid rcu lock while checking task state > that has improved overcommit cases. > > There are basically two approches for the implementation. > > Method 1: Uses per vcpu preempt flag (this series). > > Method 2: We keep a bitmap of preempted vcpus. using this we can easily > iterate over preempted vcpus. > > Note that method 2 needs an extra index variable to identify/map bitmap to > vcpu and it also needs static vcpu allocation. > > I am also posting Method 2 approach for reference in case it interests. > > Result: decent improvement for kernbench and ebizzy. > > base = 3.8.0 + undercommit patches > patched = base + preempt patches > > Tested on 32 core (no HT) mx3850 machine with 32 vcpu guest 8GB RAM > > --+-----------+-----------+-----------+------------+-----------+ > kernbench (exec time in sec lower is beter) > --+-----------+-----------+-----------+------------+-----------+ > base stdev patched stdev %improve > --+-----------+-----------+-----------+------------+-----------+ > 1x 47.0383 4.6977 44.2584 1.2899 5.90986 > 2x 96.0071 7.1873 91.2605 7.3567 4.94401 > 3x 164.0157 10.3613 156.6750 11.4267 4.47561 > 4x 212.5768 23.7326 204.4800 13.2908 3.80888 > --+-----------+-----------+-----------+------------+-----------+ > no ple kernbench 1x result for reference: 46.056133 > > --+-----------+-----------+-----------+------------+-----------+ > ebizzy (record/sec higher is better) > --+-----------+-----------+-----------+------------+-----------+ > base stdev patched stdev %improve > --+-----------+-----------+-----------+------------+-----------+ > 1x 5609.2000 56.9343 6263.7000 64.7097 11.66833 > 2x 2071.9000 108.4829 2653.5000 181.8395 28.07085 > 3x 1557.4167 109.7141 1993.5000 166.3176 28.00043 > 4x 1254.7500 91.2997 1765.5000 237.5410 40.70532 > --+-----------+-----------+-----------+------------+-----------+ > no ple ebizzy 1x result for reference : 7394.9 rec/sec > > Please let me know if you have any suggestions and comments. > > Raghavendra K T (2): > kvm: Record the preemption status of vcpus using preempt notifiers > kvm: Iterate over only vcpus that are preempted Reviewed-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx> -- 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
