linux-kernel - Re: [PATCH v2 0/3] Take the scheduling domain into account in numa balancin

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Message-ID: <20250107104824.GL20870@noisy.programming.kicks-ass.net>
Date: Tue, 7 Jan 2025 11:48:24 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Chuyi Zhou <zhouchuyi@...edance.com>
Cc: mingo@...hat.com, juri.lelli@...hat.com, vincent.guittot@...aro.org,
	dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
	mgorman@...e.de, vschneid@...hat.com, longman@...hat.com,
	riel@...riel.com, chengming.zhou@...ux.dev, kprateek.nayak@....com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/3] Take the scheduling domain into account in numa
 balancin

On Fri, Jan 03, 2025 at 08:40:18PM +0800, Chuyi Zhou wrote:
> Hello Peter,
> 
> 在 2025/1/3 19:36, Peter Zijlstra 写道:
> > Your $subject and actual patches do not patch.
> > 
> > Your subject suggests you're taking the scheduling domains into account
> > for numa balancing, your actual patches are bunch of special case hacks
> > that totally ignore the actual sched domains
> 
> The subject is indeed inappropriate, but the issues mentioned in this
> patchset still exist, right?
> 
> - We should not consider isolated CPUs in numa_stats.
> - We should not select isolated CPUs as candidate CPUs.
> 
> The current patch handle the above cases with hacks because I thought this
> kind of change is minimal to fix this issue. Perhaps you have a better
> solution for this issue? If so, please let me know, and I am more than
> willing to continue addressing this problem.

I would much rather see you do what the subject claims :-)

At the very least you should mask the whole thing against rq->rd->span
if there is a rq->rd at all ofcourse. This is not just the iteration in
update_numa_stats() but also the for_each_node_state() iteration.

I'm not sure there's anything saner than:

	cpumask_intersects(rq->rd->span, cpumask_of_node(nid))