From: Bart Van Assche <bvanassche@acm.org>
To: Ming Lei <ming.lei@redhat.com>, Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org, Tejun Heo <tj@kernel.org>,
linux-kernel@vger.kernel.org, Juri Lelli <juri.lelli@redhat.com>,
Andrew Theurer <atheurer@redhat.com>,
Joe Mario <jmario@redhat.com>, Sebastian Jug <sejug@redhat.com>,
Frederic Weisbecker <frederic@kernel.org>
Subject: Re: [PATCH V2] blk-mq: don't schedule block kworker on isolated CPUs
Date: Tue, 24 Oct 2023 09:53:49 -0700 [thread overview]
Message-ID: <293c16d2-f556-4d42-ab06-2e0acf1cc601@acm.org> (raw)
In-Reply-To: <20231013124758.1492796-1-ming.lei@redhat.com>
On 10/13/23 05:47, Ming Lei wrote:
> @@ -3926,6 +3941,15 @@ static void blk_mq_map_swqueue(struct request_queue *q)
> */
> sbitmap_resize(&hctx->ctx_map, hctx->nr_ctx);
>
> + /*
> + * rule out isolated CPUs from hctx->cpumask for avoiding to
> + * run wq worker on isolated CPU
> + */
> + for_each_cpu(cpu, hctx->cpumask) {
> + if (cpu_is_isolated(cpu))
> + cpumask_clear_cpu(cpu, hctx->cpumask);
> + }
What will happen if this code makes hctx->cpumask empty? Code like
blk_mq_first_mapped_cpu() and blk_mq_hctx_next_cpu() assumes that
hctx->cpumask is not empty. There may be other code that assumes that
hctx->cpumask is not empty.
Thanks,
Bart.
next prev parent reply other threads:[~2023-10-24 16:53 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-13 12:47 [PATCH V2] blk-mq: don't schedule block kworker on isolated CPUs Ming Lei
2023-10-18 0:52 ` Joe Mario
2023-10-23 23:45 ` Ming Lei
2023-10-24 16:53 ` Bart Van Assche [this message]
2023-10-25 1:05 ` Ming Lei
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