linux-kernel - Re: [PATCH 1/2] sched/fair: Couple wakee flips with heavy wakers

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Message-ID: <20211027090020.GO3959@techsingularity.net>
Date:   Wed, 27 Oct 2021 10:00:20 +0100
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Mike Galbraith <efault@....de>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Valentin Schneider <valentin.schneider@....com>,
        Aubrey Li <aubrey.li@...ux.intel.com>,
        Barry Song <song.bao.hua@...ilicon.com>,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] sched/fair: Couple wakee flips with heavy wakers

On Wed, Oct 27, 2021 at 04:09:12AM +0200, Mike Galbraith wrote:
> On Tue, 2021-10-26 at 14:13 +0200, Mike Galbraith wrote:
> > On Tue, 2021-10-26 at 12:57 +0100, Mel Gorman wrote:
> > > 
> > > The patch in question was also tested on other workloads on NUMA
> > > machines. For a 2-socket machine (20 cores, HT enabled so 40 CPUs)
> > > running specjbb 2005 with one JVM per NUMA node, the patch also
> > > scaled
> > > reasonably well
> > 
> > That's way more more interesting.  No idea what this thing does under
> > the hood thus whether it should be helped or not, but at least it's a
> > real deal benchmark vs a kernel hacker tool.
> 
> ...
> Installing test specjbb
> specjvm-install: Fetching from mirror
> http://mcp/mmtests-mirror/spec/SPECjbb2005_kitv1.07.tar.gz
> specjvm-install: Fetching from internet
> NOT_AVAILABLE/SPECjbb2005_kitv1.07.tar.gz
> specjvm-install: Fetching from alt internet
> /SPECjbb2005_kitv1.07.tar.gz
> FATAL specjvm-install: specjvm-install: Could not download
> /SPECjbb2005_kitv1.07.tar.gz
> FATAL specjbb-bench: specjbb install script returned error
> FATAL: specjbb returned failure, unable to continue
> FATAL: Installation step failed for specjbb
> 
> Hohum, so much for trying to take a peek.
> 

The benchmark is not available for free unfortunately.

> At any rate, unlike the tbench numbers, these have the look of signal
> rather than test jig noise, and pretty strong signal at that, so maybe
> patchlet should fly. At the very least, it appears to be saying that
> there is significant performance to be had by some means.
> 
> Bah, fly or die little patchlet.  Either way there will be winners and
> losers, that's just the way it works if you're not shaving cycles.
> 

So, I assume you are ok for patch 1 to take flight to either live or
die. I'll handle any bugs that show up in relation to it. How about
patch 2?

-- 
Mel Gorman
SUSE Labs