linux-kernel - Re: [PATCH 4/4] sched/numa: Do not move imbalanced load purely on the basis of an idle CPU

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Message-Id: <20180912102751.GB5352@linux.vnet.ibm.com>
Date:   Wed, 12 Sep 2018 15:57:52 +0530
From:   Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Mel Gorman <mgorman@...hsingularity.net>,
        Peter Zijlstra <peterz@...radead.org>,
        Rik van Riel <riel@...riel.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] sched/numa: Do not move imbalanced load purely on
 the basis of an idle CPU

> > Running SPECJbb2005. Higher bops are better.
> > 
> > Kernel A = 4.18+ 13 sched patches part of v4.19-rc1.
> > Kernel B = Kernel A + 6 patches (http://lore.kernel.org/lkml/1533276841-16341-1-git-send-email-srikar@linux.vnet.ibm.com)
> > Kernel C = Kernel B - (Avoid task migration for small numa improvement) i.e
> > 	http://lore.kernel.org/lkml/1533276841-16341-4-git-send-email-srikar@linux.vnet.ibm.com
> > 	+ 2 patches from Mel
> > 	(Do not move imbalanced load purely)
> > 	http://lore.kernel.org/lkml/20180907101139.20760-5-mgorman@techsingularity.net
> > 	(Stop comparing tasks for NUMA placement)
> > 	http://lore.kernel.org/lkml/20180907101139.20760-4-mgorman@techsingularity.net
> 
> We absolutely need the 'best' pre-regression baseline kernel measurements as well - was it 
> vanilla v4.17?
> 

I kept the baseline as 4.18.
The only revert I know since 4.16 from a numa balancing front is the one
where we unintentionally skipped task migrations.  It did somehow give good
results to a set of benchmarks but it would completely circumvent the task
migration code. I am not sure if Jirka was taking the numbers from that
kernel. From what I remember, we will pulled it out before 4.16 stabilized.