linux-kernel - Re: [PATCH] sched/topology: Improve load balancing on AMD EPYC

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Date:   Tue, 11 Jun 2019 17:22:21 +0000
From:   "Lendacky, Thomas" <Thomas.Lendacky@....com>
To:     Matt Fleming <matt@...eblueprint.co.uk>,
        Peter Zijlstra <peterz@...radead.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Suthikulpanit, Suravee" <Suravee.Suthikulpanit@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH] sched/topology: Improve load balancing on AMD EPYC

On 6/10/19 4:26 PM, Matt Fleming wrote:
> On Wed, 05 Jun, at 08:00:35PM, Peter Zijlstra wrote:
>>
>> And then we had two magic values :/
>>
>> Should we not 'fix' RECLAIM_DISTANCE for EPYC or something? Because
>> surely, if we want to load-balance agressively over 30, then so too
>> should we do node_reclaim() I'm thikning.
> 
> Yeah we can fix it just for EPYC, Mel suggested that approach originally.
> 
> Suravee, Tom, what's the best way to detect these EPYC machines that need to
> override RECLAIM_DISTANCE?

You should be able to do it based on the family. There's an init_amd_zn()
function in arch/x86/kernel/cpu/amd.c.  You can add something there or,
since init_amd_zn() sets X86_FEATURE_ZEN, you could check for that if you
prefer putting it in a different location.

Thanks,
Tom

>