Re: [4.17 regression] Performance drop on kernel-4.17 visible on Stream, Linpack and NAS parallel benchmarks

From: Mel Gorman <mgorman@techsingularity.net>
To: Jirka Hladky <jhladky@redhat.com>
Cc: Kamil Kolakowski <kkolakow@redhat.com>,
	Jakub Racek <jracek@redhat.com>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Len Brown <lenb@kernel.org>,
	linux-acpi@vger.kernel.org
Subject: Re: [4.17 regression] Performance drop on kernel-4.17 visible on Stream, Linpack and NAS parallel benchmarks
Date: Tue, 17 Jul 2018 11:03:30 +0100	[thread overview]
Message-ID: <20180717100329.yfy7igdsrpk5ujf4@techsingularity.net> (raw)
In-Reply-To: <CAE4VaGArxDYHzg8G203yKjgkuw3mULFSw8yCYbCcqvAUSUxy+A@mail.gmail.com>

On Tue, Jul 17, 2018 at 10:45:51AM +0200, Jirka Hladky wrote:
> Hi Mel,
> 
> we have compared 4.18 + git://
> git.kernel.org/pub/scm/linux/kernel/git/mel/linux.git
> sched-numa-fast-crossnode-v1r12 against 4.16 kernel and performance results
> look very good!
> 

Excellent, thanks to both Kamil and yourself for collecting the data.
It's helpful to have independent verification.

> We see performance gains about 10-20% for SPECjbb2005. NAS results are a
> little bit noisy but show overall performance gains as well (total runtime
> for reduced from 6 hours 34 minutes to 6 hours 26 minutes to give you a
> specific example).

Great.

> The only benchmark showing a slight regression is stream
> - but the regression is just a few percents ( upto 10%) and I think it's
> not a real concern given that it's an artificial benchmark.
> 

Agreed.

> How is your testing going? Do you think
> that sched-numa-fast-crossnode-v1r12 series can make it into the 4.18?
> 

My own testing completed and the results are within expectations and I
saw no red flags. Unfortunately, I consider it unlikely they'll be merged
for 4.18. Srikar Dronamraju's series is likely to need another update
and I would need to rebase my patches on top of that. Given the scope
and complexity, I find it unlikely they would be accepted for an -rc,
particularly this late of an rc. Whether we hit the 4.19 merge window or
not will depend on when Srikar's series gets updated.

> Thanks a lot for your efforts to improve the performance!

My pleasure.

-- 
Mel Gorman
SUSE Labs