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: <20180912065410.GA5352@linux.vnet.ibm.com>
Date:   Wed, 12 Sep 2018 12:24:10 +0530
From:   Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:     Mel Gorman <mgorman@...hsingularity.net>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.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

* Mel Gorman <mgorman@...hsingularity.net> [2018-09-10 10:41:47]:

> On Fri, Sep 07, 2018 at 01:37:39PM +0100, Mel Gorman wrote:
> > > Srikar's patch here:
> > > 
> > >   http://lkml.kernel.org/r/1533276841-16341-4-git-send-email-srikar@linux.vnet.ibm.com
> > > 
> > > Also frobs this condition, but in a less radical way. Does that yield
> > > similar results?
> > 
> > I can check. I do wonder of course if the less radical approach just means
> > that automatic NUMA balancing and the load balancer simply disagree about
> > placement at a different time. It'll take a few days to have an answer as
> > the battery of workloads to check this take ages.
> > 
> 
> Tests completed over the weekend and I've found that the performance of
> both patches are very similar for two machines (both 2 socket) running a
> variety of workloads. Hence, I'm not worried about which patch gets picked
> up. However, I would prefer my own on the grounds that the additional
> complexity does not appear to get us anything. Of course, that changes if
> Srikar's tests on his larger ppc64 machines show the more complex approach
> is justified.
> 

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

To me, Kernel B which is the 13 patches accepted in v4.19-rc1 + 6 patches
posted for review seem to be giving better performance.

The numbers are compared to previous kernel i.e
for Kernel A, v4.18 is prev
for kernel B, Kernel A is prev
for Kernel C, B is prev

2 node x86 Haswell

v4.18 or 94710cac0ef4
JVMS  Prev    Current  %Change
4     203769
1     316734

Kernel A
JVMS  Prev    Current  %Change
4     203769  209790   2.95482
1     316734  312377   -1.3756

Kernel B
JVMS  Prev    Current  %Change
4     209790  202059   -3.68511
1     312377  326987   4.67704

Kernel C
JVMS  Prev    Current  %Change
4     202059  200681   -0.681979
1     326987  316715   -3.14141

================================================


4 Node / 2 Socket PowerNV / Power 8

v4.18 or 94710cac0ef4
JVMS  Prev    Current  %Change
8     88411.9
1     222075

Kernel A
JVMS  Prev     Current  %Change
8     88411.9  88733.5  0.363752
1     222075   214607   -3.36283

Kernel B
JVMS  Prev     Current  %Change
8     88733.5  89952    1.37321
1     214607   217226   1.22037

Kernel C
JVMS  Prev    Current  %Change
8     89952   89912.9  -0.0434676
1     217226  219281   0.946019


================================================


2 Node / 2 Socket Power 9 / PowerNV

v4.18 or 94710cac0ef4
JVMS  Prev    Current  %Change
4     195989
1     202854

Kernel A
JVMS  Prev    Current  %Change
4     195989  193108   -1.46998
1     202854  204042   0.585643

Kernel B
JVMS  Prev    Current  %Change
4     193108  196422   1.71614
1     204042  211219   3.51741

Kernel C
JVMS  Prev    Current  %Change
4     196422  195052   -0.697478
1     211219  207854   -1.59313


================================================

4 Node / 4 Socket Power 7 PhyP LPAR.

v4.18 or 94710cac0ef4
JVMS  Prev    Current  %Change
8     52826.9
1     103103

Kernel A
JVMS  Prev     Current  %Change
8     52826.9  59504.4  12.6403
1     103103   102542   -0.544116

Kernel B
JVMS  Prev     Current  %Change
8     59504.4  61674.8  3.64746
1     102542   108211   5.52847

Kernel C
JVMS  Prev     Current  %Change
8     61674.8  57946.5  -6.04509
1     108211   104533   -3.39892