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

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Date:   Mon, 22 Jul 2019 14:11:12 +0000
From:   "Suthikulpanit, Suravee" <Suravee.Suthikulpanit@....com>
To:     Matt Fleming <matt@...eblueprint.co.uk>
CC:     Mel Gorman <mgorman@...hsingularity.net>,
        Peter Zijlstra <peterz@...radead.org>,
        "Lendacky, Thomas" <Thomas.Lendacky@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH] sched/topology: Improve load balancing on AMD EPYC

Matt

On 6/28/2019 10:15 AM, Matt Fleming wrote:
> On Wed, 26 Jun, at 09:18:01PM, Suthikulpanit, Suravee wrote:
>>
>> We use 16 to designate 1-hop latency (for different node within the same socket).
>> For across-socket access, since the latency is greater, we set the latency to 32
>> (twice the latency of 1-hop) not aware of the RECLAIM_DISTANCE at the time.
>   
> I guess the question is: Is the memory latency of a remote node 1 hop
> away 1.6x the local node latency?
> 

Yes, remote node 1 hop is 1.6x the local node latency for AMD EPYC.

Suravee