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

From: Lendacky, Thomas
Date: Tue Jun 11 2019 - 13:26:55 EST

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

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.