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From:   Aubrey Li <aubrey.intel@gmail.com>
Date:   Wed, 24 Apr 2019 21:13:10 +0800
Message-ID: <CAERHkrtOCbLQ-tFq9ujjnyaudtd_e0UaSA2GQG64JqdS6cuTKg@mail.gmail.com>
Subject: Re: [RFC PATCH v2 00/17] Core scheduling v2
To:     Vineeth Remanan Pillai <vpillai@digitalocean.com>
Cc:     Nishanth Aravamudan <naravamudan@digitalocean.com>,
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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?

Thanks,
-Aubrey