linux-kernel - Re: [RFC][PATCH] sched: Cache aware load-balancing

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Message-ID: <20250326094242.GD25239@noisy.programming.kicks-ass.net>
Date: Wed, 26 Mar 2025 10:42:42 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: "Chen, Yu C" <yu.c.chen@...el.com>
Cc: K Prateek Nayak <kprateek.nayak@....com>, juri.lelli@...hat.com,
	vincent.guittot@...aro.org, dietmar.eggemann@....com,
	rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
	vschneid@...hat.com, linux-kernel@...r.kernel.org,
	tim.c.chen@...ux.intel.com, tglx@...utronix.de, len.brown@...el.com,
	gautham.shenoy@....com, mingo@...nel.org, yu.chen.surf@...mail.com
Subject: Re: [RFC][PATCH] sched: Cache aware load-balancing

On Wed, Mar 26, 2025 at 05:15:24PM +0800, Chen, Yu C wrote:
> Thanks for running the test. I think hackbenc/schbench would be the good
> benchmarks to start with. I remember that you and Gautham mentioned that
> schbench prefers to be aggregated in a single LLC in LPC2021 or 2022. I ran
> a schbench test using mmtests on a Xeon server which has 4 NUMA nodes. Each
> node has 80 cores (with SMT disabled). The numa=off option was appended to
> the boot commandline, so there are 4 "LLCs" within each node.

We really should look at getting the SnC topology even without SnC being
in use.

The sheer size of these LLCs is untenable.