linux-kernel - Re: [PATCH 4/7] sched/fair: Avoid unnecessary balancing of asymmetric capacity groups

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Date:   Mon, 19 Feb 2018 15:53:35 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Morten Rasmussen <morten.rasmussen@....com>
Cc:     mingo@...hat.com, valentin.schneider@....com,
        dietmar.eggemann@....com, vincent.guittot@...aro.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/7] sched/fair: Avoid unnecessary balancing of
 asymmetric capacity groups

On Mon, Feb 19, 2018 at 03:50:12PM +0100, Peter Zijlstra wrote:
> On Thu, Feb 15, 2018 at 04:20:51PM +0000, Morten Rasmussen wrote:
> > On systems with asymmetric cpu capacities, a skewed load distribution
> > might yield better throughput than balancing load per group capacity.
> > For example, preferring high capacity cpus for compute intensive tasks
> > leaving low capacity cpus idle rather than balancing the number of idle
> > cpus across different cpu types. Instead, let load-balance back off if
> > the busiest group isn't really overloaded.
> 
> I'm sorry. I just can't seem to make sense of that today. What?

Aah, you're saying that is we have 4+4 bit.little and 4 runnable tasks,
we would like them running on our big cluster and leave the small
cluster entirely idle, instead of runnint 2+2.

So what about this DynamicQ nonsense? Or is that so unstructured we
can't really do anything sensible with it?