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

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Date:   Thu, 21 Jun 2018 10:23:32 +0100
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Jirka Hladky <jhladky@...hat.com>
Cc:     Jakub Racek <jracek@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>, linux-acpi@...r.kernel.org,
        "kkolakow@...hat.com" <kkolakow@...hat.com>
Subject: Re: [4.17 regression] Performance drop on kernel-4.17 visible on
 Stream, Linpack and NAS parallel benchmarks

On Wed, Jun 20, 2018 at 07:25:19PM +0200, Jirka Hladky wrote:
> Hi Mel and others,
> 
> I would like to let you know that I have tested following patch
> 

Understood. FWIW, there is a lot in flight at the moment but the first
likely patch is removing rate limiting entirely and see what falls out.
The rest of the experiment series deals with fast-scan-start, reset of
preferred_nid on cross-node load balancing and dealing with THP false
sharing but it's all preliminary and untested.

Furthermore, matters have been complicated by the posting of "Fixes for
sched/numa_balancing". My own testing indicates that this helped which
means that I need to review this first and then rebase anything else on
top of it.

I would also suggest you test that series paying particular attention to
whether it a) improves performance and b) how close it gets to the
revert in terms of overall performance.

-- 
Mel Gorman
SUSE Labs