linux-kernel - Re: [RFC,v2 3/3] sched: ignore task_h_load for CPU_NEWLY

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Message-ID: <20170209122218.GE6500@twins.programming.kicks-ass.net>
Date:   Thu, 9 Feb 2017 13:22:18 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Uladzislau Rezki <urezki@...il.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Uladzislau 2 Rezki <uladzislau2.rezki@...ymobile.com>
Subject: Re: [RFC,v2 3/3] sched: ignore task_h_load for CPU_NEWLY_IDLE

On Wed, Feb 08, 2017 at 09:43:29AM +0100, Uladzislau Rezki wrote:
> From: Uladzislau 2 Rezki <uladzislau2.rezki@...ymobile.com>
> 
> A load balancer calculates imbalance factor for particular shed
> domain and tries to steal up the prescribed amount of weighted load.
> However, a small imbalance factor would sometimes prevent us from
> stealing any tasks at all. When a CPU is newly idle, it should
> steal first task which passes a migration criteria.
> 

So ideally we'd reduce the number of special cases instead of increase
them. Does this patch make an actual difference, if so how much and with
what workload?

Also, I suppose that if we finally manage to parameterize the whole
load-balancing to act on: nr_running/util/load depending on the domain
this all naturally falls into place.