linux-kernel - Re: [PATCH v2] workqueue: Automatic affinity scope fallback for single-pod topologies

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Message-ID: <aYUVVuIidMpuYy3j@slm.duckdns.org>
Date: Thu, 5 Feb 2026 12:10:30 -1000
From: Tejun Heo <tj@...nel.org>
To: Chuck Lever <cel@...nel.org>
Cc: jiangshanlai@...il.com, linux-kernel@...r.kernel.org,
	Chuck Lever <chuck.lever@...cle.com>
Subject: Re: [PATCH v2] workqueue: Automatic affinity scope fallback for
 single-pod topologies

Hello, Chuck.

On Wed, Feb 04, 2026 at 09:49:11PM -0500, Chuck Lever wrote:
> +static bool __init cpus_share_cluster(int cpu0, int cpu1)
> +{
> +	return cpumask_test_cpu(cpu0, topology_cluster_cpumask(cpu1));
> +}

Cluster boundary == core boundary for a lot of CPUs. I don't think this is
going to work. Here are a couple options:

- Introduce an affinity level which splits CACHE according to some
  adjustable heuristics.

- Make the NFS workqueue default to WQ_AFFN_CORE (or maybe switch based on
  some heuristics) or switch to a per-cpu workqueue.

Thanks.

-- 
tejun