linux-kernel - Re: [REGRESSION] sched/fair: Reimplement NEXT

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Message-ID: <7341009d-b3e7-40bc-83b3-401e6e164ef5@arm.com>
Date: Mon, 5 Jan 2026 16:33:30 +0000
From: Ryan Roberts <ryan.roberts@....com>
To: Shrikanth Hegde <sshegde@...ux.ibm.com>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org,
 Aishwarya TCV <Aishwarya.TCV@....com>,
 Dietmar Eggemann <dietmar.eggemann@....com>,
 Mel Gorman <mgorman@...hsingularity.net>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>
Subject: Re: [REGRESSION] sched/fair: Reimplement NEXT_BUDDY to align with
 EEVDF goals

On 05/01/2026 14:38, Shrikanth Hegde wrote:
> 
> Hi Ryan,
> 
>>> node distances:
>>> node   0   1
>>>    0:  10  20
>>>    1:  20  10
>>>
>>> Whereas I assume the Graviton3 has 64 CPUs (cores) flat in a single MC
>>> domain? I guess topology has influence in benchmark numbers here as well.
>>
>> I can't easily enable scheduler debugging right now (which I think is needed to
>> get this info directly?). But that's what I'd expect, yes. lscpu confirms there
>> is a single NUMA node and topology for cpu0 gives this if it helps:
> 
> If you dump /proc/schedstat it should give you topology info as well.
> 
> (you will need to parse it depending on which CPU you are looking this from)

Ahh yes, thanks!

Every cpu is reported as being in "domain0 MC ffffffff,ffffffff". So I guess
that means there is a single MC domain as Dietmar suggests.

Thanks,
Ryan