linux-kernel - Re: Scheduler patches: 6x performance increase when system is under heavy load

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Date:   Wed, 14 Dec 2016 00:15:25 -0500
From:   Alexandre-Xavier Labonté-Lamoureux 
        <axdoomer@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org
Subject: Re: Scheduler patches: 6x performance increase when system is under
 heavy load

> Which of the 4 patches does this?

I used all the 4 patches at the same time. Each patch fixes a
different bug. Would you like me to try each of them individually?
Were you already aware of each of these bugs?

> Also, what hypervisor are you using and what does the output of booting
> with "sched_debug" look like?

I was running the distro in VirualBox on Fedora. Here's the info from
/proc/sched_debug:
https://justpaste.it/11dhb
dmesg: https://justpaste.it/11dhr

> Lastly, can you reproduce on real hardware?

No. On real hardware, I tested in Ubuntu on an i7-4790 3.60GHz CPU
without disabling HT and I saw no difference between CFS, the patched
kernel and MuQSS. If I get to know a reason why one would be better
than the other, I'd take the time to test it on more hardware. I'm
curious how I got such a performance improvement in my VM.

On Tue, Dec 13, 2016 at 8:40 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Sun, Dec 11, 2016 at 04:41:51PM -0500, Alexandre-Xavier Labonté-Lamoureux wrote:
>>
>> Here are my results (using "time make -j32" on my VM that has 4 cores):
>>
>> Kernel 4.8.14
>>   real 26m56.151s
>>   user 79m52.472s
>>   sys 7m42.964s
>>
>> Same kernel, but patched:
>>   real 4m25.238s
>>   user 13m52.932s
>>   sys 1m25.820s
>>
>> I hope you guys will look into this.
>
> Which of the 4 patches does this?
>
> Also, what hypervisor are you using and what does the output of booting
> with "sched_debug" look like?
>
> Lastly, can you reproduce on real hardware?