Messages in this thread | | | Date | Thu, 25 Apr 2019 11:55:08 +0200 | From | Ingo Molnar <> | Subject | Re: [RFC PATCH v2 00/17] Core scheduling v2 |
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* Aubrey Li <aubrey.intel@gmail.com> wrote:
> On Wed, Apr 24, 2019 at 10:00 PM Julien Desfossez > <jdesfossez@digitalocean.com> wrote: > > > > On 24-Apr-2019 09:13:10 PM, Aubrey Li wrote: > > > On Wed, Apr 24, 2019 at 12:18 AM Vineeth Remanan Pillai > > > <vpillai@digitalocean.com> wrote: > > > > > > > > Second iteration of the core-scheduling feature. > > > > > > > > This version fixes apparent bugs and performance issues in v1. This > > > > doesn't fully address the issue of core sharing between processes > > > > with different tags. Core sharing still happens 1% to 5% of the time > > > > based on the nature of workload and timing of the runnable processes. > > > > > > > > Changes in v2 > > > > ------------- > > > > - rebased on mainline commit: 6d906f99817951e2257d577656899da02bb33105 > > > > > > Thanks to post v2, based on this version, here is my benchmarks result. > > > > > > Environment setup > > > -------------------------- > > > Skylake server, 2 numa nodes, 104 CPUs (HT on) > > > cgroup1 workload, sysbench (CPU intensive non AVX workload) > > > cgroup2 workload, gemmbench (AVX512 workload) > > > > > > Case 1: task number < CPU num > > > -------------------------------------------- > > > 36 sysbench threads in cgroup1 > > > 36 gemmbench threads in cgroup2 > > > > > > core sched off: > > > - sysbench 95th percentile latency(ms): avg = 4.952, stddev = 0.55342 > > > core sched on: > > > - sysbench 95th percentile latency(ms): avg = 3.549, stddev = 0.04449 > > > > > > Due to core cookie matching, sysbench tasks won't be affect by AVX512 > > > tasks, latency has ~28% improvement!!! > > > > > > Case 2: task number > CPU number > > > ------------------------------------------------- > > > 72 sysbench threads in cgroup1 > > > 72 gemmbench threads in cgroup2 > > > > > > core sched off: > > > - sysbench 95th percentile latency(ms): avg = 11.914, stddev = 3.259 > > > core sched on: > > > - sysbench 95th percentile latency(ms): avg = 13.289, stddev = 4.863 > > > > > > So not only power, now security and performance is a pair of contradictions. > > > Due to core cookie not matching and forced idle introduced, latency has ~12% > > > regression. > > > > > > Any comments? > > > > Would it be possible to post the results with HT off as well ? > > What's the point here to turn HT off? The latency is sensitive to the > relationship > between the task number and CPU number. Usually less CPU number, more run > queue wait time, and worse result.
HT-off numbers are mandatory: turning HT off is by far the simplest way to solve the security bugs in these CPUs.
Any core-scheduling solution *must* perform better than HT-off for all relevant workloads, otherwise what's the point?
Thanks,
Ingo
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