linux-kernel - Re: hackbench vs select_idle_sibling; was: [tip:sched/core] sched/fair, cpumask: Export for_each_cpu

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Message-ID: <acecfe24-2e31-f560-91bc-93e7e08c109c@fb.com>
Date:   Fri, 9 Jun 2017 13:52:06 -0400
From:   Chris Mason <clm@...com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Matt Fleming <matt@...eblueprint.co.uk>
CC:     <mingo@...nel.org>, <tglx@...utronix.de>, <riel@...hat.com>,
        <hpa@...or.com>, <efault@....de>, <linux-kernel@...r.kernel.org>,
        <torvalds@...ux-foundation.org>, <lvenanci@...hat.com>,
        <xiaolong.ye@...el.com>, <kitsunyan@...ox.ru>
Subject: Re: hackbench vs select_idle_sibling; was: [tip:sched/core]
 sched/fair, cpumask: Export for_each_cpu_wrap()

On 06/06/2017 05:21 AM, Peter Zijlstra wrote:
> On Mon, Jun 05, 2017 at 02:00:21PM +0100, Matt Fleming wrote:
>> On Fri, 19 May, at 04:00:35PM, Matt Fleming wrote:
>>> On Wed, 17 May, at 12:53:50PM, Peter Zijlstra wrote:
>>>>
>>>> Please test..
>>>
>>> Results are still coming in but things do look better with your patch
>>> applied.
>>>
>>> It does look like there's a regression when running hackbench in
>>> process mode and when the CPUs are not fully utilised, e.g. check this
>>> out:
>>
>> This turned out to be a false positive; your patch improves things as
>> far as I can see.
>
> Hooray, I'll move it to a part of the queue intended for merging.

It's a little late, but Roman Gushchin helped get some runs of this with 
our production workload.  The patch is every so slightly better.

Thanks!

-chris