linux-kernel - Re: [RFC PATCH v1] blk-mq: isolate CPUs from hctx

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Message-ID: <qlq56cpm5enxoevqstziz7hxp5lqgs74zl2ohv4shynasxuho6@xb5hk5cunhfn>
Date: Fri, 15 Nov 2024 16:45:24 +0100
From: Michal Koutný <mkoutny@...e.com>
To: Costa Shulyupin <costa.shul@...hat.com>
Cc: ming.lei@...hat.com, Jens Axboe <axboe@...nel.dk>, 
	Waiman Long <longman@...hat.com>, Tejun Heo <tj@...nel.org>, Johannes Weiner <hannes@...xchg.org>, 
	linux-block@...r.kernel.org, linux-kernel@...r.kernel.org, cgroups@...r.kernel.org, 
	Daniel Wagner <dwagner@...e.de>
Subject: Re: [RFC PATCH v1] blk-mq: isolate CPUs from hctx

Hello.

On Fri, Nov 08, 2024 at 07:48:30AM GMT, Costa Shulyupin <costa.shul@...hat.com> wrote:
> Cgroups allow configuring isolated_cpus at runtime.
> However, blk-mq may still use managed interrupts on the
> newly isolated CPUs.
> 
> Rebuild hctx->cpumask considering isolated CPUs to avoid
> managed interrupts on those CPUs and reclaim non-isolated ones.
> 
> The patch is based on
> isolation: Exclude dynamically isolated CPUs from housekeeping masks:
> https://lore.kernel.org/lkml/20240821142312.236970-1-longman@redhat.com/

Even based on that this seems incomplete to me the CPUs that are part of
isolcpus mask on boot time won't be excluded from this?
IOW, isolating CPUs from blk_mq_hw_ctx would only be possible via cpuset
but not "statically" throught the cmdline option, or would it?

Thanks,
Michal

(-Cc: lizefan.x@...edance.com)

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