linux-kernel - Re: [RESEND PATCH v3 0/7] Improve scheduler scalability for fast path

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Date:   Mon, 8 Jul 2019 15:32:31 -0700
From:   Tim Chen <tim.c.chen@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Patrick Bellasi <patrick.bellasi@....com>
Cc:     subhra mazumdar <subhra.mazumdar@...cle.com>,
        linux-kernel@...r.kernel.org, mingo@...hat.com, tglx@...utronix.de,
        steven.sistare@...cle.com, dhaval.giani@...cle.com,
        daniel.lezcano@...aro.org, vincent.guittot@...aro.org,
        viresh.kumar@...aro.org, mgorman@...hsingularity.net,
        Paul Turner <pjt@...gle.com>, riel@...riel.com,
        morten.rasmussen@....com, Aubrey Li <aubrey.li@...ux.intel.com>
Subject: Re: [RESEND PATCH v3 0/7] Improve scheduler scalability for fast path

On 7/1/19 7:04 AM, Peter Zijlstra wrote:
> On Mon, Jul 01, 2019 at 02:55:52PM +0100, Patrick Bellasi wrote:
>> On 01-Jul 11:02, Peter Zijlstra wrote:
> 
>>> Some of the things we could tie to this would be:
>>>
>>>   - select_idle_siblings; -nice would scan more than +nice,
>>
>> Just to be sure, you are not proposing to use the nice value we
>> already have, i.e.
>>   p->{static,normal}_prio
>> but instead a new similar concept, right?
> 
> Correct; a new sched_attr::sched_latency_nice value, which is like
> sched_nice, but controls a different dimmension of behaviour.
> 

I think the sched_latency_nice value could be also useful for AVX512 for x86.
Running an AVX512 task could drop frequency of the cpu, including the sibling
hardware thread.  So scheduling task that don't mind latency on the
sibling while an AVX512 task runs will make sense.

Tim