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SubjectRe: Abysmal scheduler performance in Linus' tree?
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> On Sep 6, 2017, at 1:25 AM, Peter Zijlstra <peterz@infradead.org> wrote:
>
>> On Tue, Sep 05, 2017 at 10:13:39PM -0700, Andy Lutomirski wrote:
>> I'm running e7d0c41ecc2e372a81741a30894f556afec24315 from Linus' tree
>> today, and I'm seeing abysmal scheduler performance. Running make -j4
>> ends up with all the tasks on CPU 3 most of the time (on my
>> 4-logical-thread laptop). taskset -c 0 whatever puts whatever on CPU
>> 0, but plain while true; do true; done puts the infinite loop on CPU 3
>> right along with the make -j4 tasks.
>>
>> This is on Fedora 26, and I don't think I'm doing anything weird.
>> systemd has enabled the cpu controller, but it doesn't seem to have
>> configured anything or created any non-root cgroups.
>>
>> Just a heads up. I haven't tried to diagnose it at all.
>
> "make O=defconfig-build -j80" results in:
>
> %Cpu0 : 90.7 us, 9.3 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu1 : 88.7 us, 11.3 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu2 : 93.5 us, 6.5 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu3 : 86.8 us, 13.2 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu4 : 89.7 us, 10.3 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu5 : 96.3 us, 3.7 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu6 : 95.3 us, 4.7 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu7 : 94.4 us, 5.6 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu8 : 91.7 us, 8.3 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu9 : 94.3 us, 5.7 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu10 : 90.7 us, 9.3 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu11 : 96.2 us, 3.8 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu12 : 91.5 us, 8.5 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu13 : 90.6 us, 9.4 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu14 : 97.2 us, 2.8 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu15 : 89.7 us, 10.3 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu16 : 90.6 us, 9.4 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu17 : 93.4 us, 6.6 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu18 : 90.6 us, 9.4 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu19 : 92.5 us, 7.5 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu20 : 94.4 us, 5.6 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu21 : 90.7 us, 9.3 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu22 : 92.5 us, 7.5 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu23 : 90.7 us, 9.3 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu24 : 91.6 us, 8.4 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu25 : 93.5 us, 6.5 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu26 : 93.4 us, 5.7 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.9 si, 0.0 st
> %Cpu27 : 92.5 us, 7.5 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu28 : 92.5 us, 7.5 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu29 : 88.8 us, 11.2 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu30 : 90.6 us, 9.4 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu31 : 93.5 us, 6.5 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu32 : 93.5 us, 6.5 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu33 : 93.4 us, 6.6 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu34 : 90.7 us, 9.3 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu35 : 93.5 us, 6.5 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu36 : 90.7 us, 9.3 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu37 : 97.2 us, 2.8 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu38 : 92.5 us, 7.5 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
> %Cpu39 : 92.6 us, 7.4 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
>
> Do you have a .config somewhere?

I'll attach tomorrow. I'll also test in a VM.

> Are you running with the systemd? Is it
> creating cpu cgroups?

Yes systemd, no cgroups.

>
> Any specifics on your setup?

On further fiddling, I only see this after a suspend and resume cycle.
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