linux-kernel - Re: [RFC PATCH 3/3] sched: introduce tunables to control soft affinity

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Message-Id: <20190718100816.GA19218@linux.vnet.ibm.com>
Date:   Thu, 18 Jul 2019 15:38:16 +0530
From:   Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:     subhra mazumdar <subhra.mazumdar@...cle.com>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        mingo@...hat.com, tglx@...utronix.de, prakash.sangappa@...cle.com,
        dhaval.giani@...cle.com, daniel.lezcano@...aro.org,
        vincent.guittot@...aro.org, viresh.kumar@...aro.org,
        tim.c.chen@...ux.intel.com, mgorman@...hsingularity.net
Subject: Re: [RFC PATCH 3/3] sched: introduce tunables to control soft
 affinity

* subhra mazumdar <subhra.mazumdar@...cle.com> [2019-06-26 15:47:18]:

> For different workloads the optimal "softness" of soft affinity can be
> different. Introduce tunables sched_allowed and sched_preferred that can
> be tuned via /proc. This allows to chose at what utilization difference
> the scheduler will chose cpus_allowed over cpus_preferred in the first
> level of search. Depending on the extent of data sharing, cache coherency
> overhead of the system etc. the optimal point may vary.
> 
> Signed-off-by: subhra mazumdar <subhra.mazumdar@...cle.com>
> ---

Correct me but this patchset only seems to be concentrated on the wakeup
path, I don't see any changes in the regular load balancer or the
numa-balancer. If system is loaded or tasks are CPU intensive, then wouldn't
these tasks be moved to cpus_allowed instead of cpus_preferred and hence
breaking this soft affinity.

-- 
Thanks and Regards
Srikar Dronamraju