Re: [PATCH 4/4] sched/fair: Proportional newidle balance

Peter Zijlstra
2026-01-27T08:44:21Z

On Sun, Jan 25, 2026 at 12:22:21PM +0000, Mohamed Abuelfotoh, Hazem wrote:
> I can confirm that we are seeing a 4-11% performance regression in v6.12.66
> on multiple benchmarks running on c7a.4xlarge AWS EC2 instances that are
> powered by AMD EPYC 9R14-series CPU (code-named Genoa) and c7i.4xlarge which
> is powered by 4th-Generation Intel Xeon Scalable processor (code-named
> Sapphire Rapids).

For those not speaking Amazon; what actual system setup is that Xeon? Is
that single socket or multi-socket?

Going by the name, the 4x would suggest a quad-socket Xeon, which are
somewhat beastly, but if I google this 'c7i.4xlarge' identifier, I get a
puny single socket 16cpu thing.

What is it?