linux-kernel - Re: [RFC PATCH v4 00/19] Core scheduling v4

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Date:   Fri, 21 Feb 2020 18:20:57 -0500
From:   Julien Desfossez <jdesfossez@...italocean.com>
To:     Vineeth Remanan Pillai <vpillai@...italocean.com>
Cc:     Aubrey Li <aubrey.intel@...il.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Nishanth Aravamudan <naravamudan@...italocean.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Paul Turner <pjt@...gle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Dario Faggioli <dfaggioli@...e.com>,
        Frédéric Weisbecker <fweisbec@...il.com>,
        Kees Cook <keescook@...omium.org>,
        Greg Kerr <kerrnel@...gle.com>, Phil Auld <pauld@...hat.com>,
        Aaron Lu <aaron.lwe@...il.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [RFC PATCH v4 00/19] Core scheduling v4

On 18-Feb-2020 04:58:02 PM, Vineeth Remanan Pillai wrote:
> > Yes, this makes sense, patch updated at here, I put your name there if
> > you don't mind.
> > https://github.com/aubreyli/linux/tree/coresched_v4-v5.5.2-rc2
> >
> > Thanks Aubrey!

Just a quick note, I ran a very cpu-intensive benchmark (9x12 vcpus VMs
running linpack), all affined to an 18 cores NUMA node (36 hardware
threads). Each VM is running in its own cgroup/tag with core scheduling
enabled. We know it already performed much better than nosmt, so for
this case, I measured various co-scheduling statistics:
- how much time the process spends co-scheduled with idle, a compatible
  or an incompatible task
- how long does the process spends running in a inefficient
  configuration (more than 1 thread running alone on a core)

And I am very happy to report than even though the 9 VMs were configured
to float on the whole NUMA node, the scheduler / load-balancer did a
very good job at keeping an efficient configuration:

Process 10667 (qemu-system-x86), 10 seconds trace:
  - total runtime: 46451472309 ns,
  - local neighbors (total: 45713285084 ns, 98.411 % of process runtime):
  - idle neighbors (total: 484054061 ns, 1.042 % of process runtime):
  - foreign neighbors (total: 4191002 ns, 0.009 % of process runtime):
  - unknown neighbors  (total: 92042503 ns, 0.198 % of process runtime)
  - inefficient periods (total: 464832 ns, 0.001 % of process runtime):
    - number of periods: 48
    - min period duration: 1424 ns
    - max period duration: 116988 ns
    - average period duration: 9684.000 ns
    - stdev: 19282.130

I thought you would enjoy seeing this :-)

Have a good weekend,

Julien