Re: [PATCH] sched/fair: allow imbalance between LLCs under NUMA

[Jianyong Wu]

Hi Prateek,

On 6/19/2025 2:30 PM, K Prateek Nayak wrote:
> Hello Jianyong,
>
> On 6/19/2025 11:38 AM, Jianyong Wu wrote:
> > If this change has bad effect for performance, is there any suggestion
> > to mitigate the iperf migration issue?
>
> How big of a performance difference are you seeing? I still don't see
> any numbers from your testing on the thread.

Sorry for that. Here is the data.

On a machine with 8 NUMAs, each with 4 LLCs, totally 128 cores with smt2.

test command:
server: iperf3 -s
client: iperf3 -c 127.0.0.1 -t 100 -i 2

==================================================
default                  allow imb
25.3 Gbits/sec           26.7 Gbits/sec     +5.5%
==================================================


> > Or just leave it there?
>
> Ideally, the cache-aware load balancing series [1] should be able to
> address these concerns. I suggest testing iperf with those changes and
> checking if that solves the issues of excessive migration.
>
> [1] https://lore.kernel.org/lkml/ 
> cover.1750268218.git.tim.c.chen@xxxxxxxxxxxxxxx/

I know this patch set. Maybe a little heave. I'll check for iperf test.

Thanks
Jianyong