Messages in this thread | | | From | Nikunj A Dadhania <> | Subject | Re: [RFC PATCH 0/4] Gang scheduling in CFS | Date | Thu, 05 Jan 2012 12:27:32 +0530 |
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On Wed, 04 Jan 2012 19:13:15 +0200, Avi Kivity <avi@redhat.com> wrote: > On 01/04/2012 04:56 PM, Srivatsa Vaddagiri wrote: > > * Avi Kivity <avi@redhat.com> [2012-01-04 16:41:58]: > > > > > > Here are some observation related to Baseline-only(8vm case) > > > > > > > > | ple_gap=128 | ple_gap=64 | ple_gap=256 | ple_window=2048 > > > > --------------+-------------+------------+-------------+---------------- > > > > EbzyRecords/s | 2247.50 | 2132.75 | 2086.25 | 1835.62 > > > > PauseExits | 7928154.00 | 6696342.00 | 7365999.00 | 50319582.00 > > > > > > > > With ple_window = 2048, PauseExits is more than 6times the default case > > > > > > So it looks like the default is optimal, at least wrt the cases you > > > tested and your test workload. > > > > The default case still lags considerably behind the results we are seeing with > > gang scheduling. One more interesting data point would be to see how > > many PLE exits we are seeing when the vcpu is spinning in > > flush_tlb_others_ipi(). Is there any easy way to determine that? > > > > You could get an exit trace (trace-cmd -e kvm:kvm_exit) and filter on > PLE exits; the trace contains the guest %rip, so you could match it > against flush_tlb_others_ipi(). > Cool, this is much easier, had to do some awk script to extract PLE exits wrt flush_tlb_others_ipi:
Matched 9382616(86%), Not matched 1453845(14%)
So considerable ple exits are from flush_tlb_others_ipi and even then we see:
35.01% ebizzy [kernel.kallsyms] [k] flush_tlb_others_ipi
Nikunj
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