linux-kernel - Re: [SCHEDULER] Performance drop in 4.19 compared to 4.18 kernel

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Date:   Mon, 17 Sep 2018 14:06:29 +0100
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Jirka Hladky <jhladky@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        Jakub Ra??ek <jracek@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "kkolakow@...hat.com" <kkolakow@...hat.com>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [SCHEDULER] Performance drop in 4.19 compared to 4.18 kernel

On Fri, Sep 14, 2018 at 04:50:20PM +0200, Jirka Hladky wrote:
> Hi Peter and Srikar,
> 
> > I have bounced the 5 patches to you, (one of the 6 has not been applied by
> > Peter) so I have skipped that.
> > They can also be fetched from
> > http://lore.kernel.org/lkml/1533276841-16341-1-git-send-email-srikar@linux.vnet.ibm.com
> 
> I'm sorry for the delay, we have finally the results for the above
> kernel. The performance results look good compared to 4.19 vanilla and
> are about the same as Mel's sched-numa-fast-crossnode-v1r12 patch set
> for 4.18:
> 
> Compared to kernel-4.19.0-0.rc1.1
> 
>   * Improvement upto 20% for SPECjbb2005, SPECjvm2008 benchmarks
>   * Improvement upto 50% for stream benchmark
>   * Improvement upto 100% for the NAS benchmark (sp_C subtest, 8
> threads on 4 NUMA system with 4x E5-4610 v2 @ 2.30GHz, 64 cores in
> total)
> 
> When I compare it against Mel's patchset
> (git://git.kernel.org/pub/scm/linux/kernel/git/mel/linux.git
> sched-numa-fast-crossnode-v1r12)
> 
>   * Mel's kernel is about 15% faster for stream benchmarks
>   * The other benchmarks show very similar results with both kernels
> 
> Mel's patchset eliminates NUMA migration rate limits, this is
> presumbly the reason for the good stream results.
> 
> Do you have any update when the current patchset could be merged into
> the upstream kernel?
> 

I'm travelling at the moment but when I get back, I'll see what's in the
tip tree with respect to Srikar's patches and then rebase the fast-migration
patches on top and reconfirm they still behave as expected. Assuming
they do, I'll resend them.