linux-kernel - Re: [PATCH v7 09/10] blk-mq: prevent offlining hk CPUs with associated online isolated CPUs

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Message-ID: <66bfaac0-03aa-4957-80a7-0f004bb2dc58@suse.de>
Date: Thu, 3 Jul 2025 08:58:45 +0200
From: Hannes Reinecke <hare@...e.de>
To: Daniel Wagner <wagi@...nel.org>, Jens Axboe <axboe@...nel.dk>,
 Keith Busch <kbusch@...nel.org>, Christoph Hellwig <hch@....de>,
 Sagi Grimberg <sagi@...mberg.me>, "Michael S. Tsirkin" <mst@...hat.com>
Cc: Aaron Tomlin <atomlin@...mlin.com>,
 "Martin K. Petersen" <martin.petersen@...cle.com>,
 Thomas Gleixner <tglx@...utronix.de>, Costa Shulyupin
 <costa.shul@...hat.com>, Juri Lelli <juri.lelli@...hat.com>,
 Valentin Schneider <vschneid@...hat.com>, Waiman Long <llong@...hat.com>,
 Ming Lei <ming.lei@...hat.com>, Frederic Weisbecker <frederic@...nel.org>,
 Mel Gorman <mgorman@...e.de>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
 linux-nvme@...ts.infradead.org, megaraidlinux.pdl@...adcom.com,
 linux-scsi@...r.kernel.org, storagedev@...rochip.com,
 virtualization@...ts.linux.dev, GR-QLogic-Storage-Upstream@...vell.com
Subject: Re: [PATCH v7 09/10] blk-mq: prevent offlining hk CPUs with
 associated online isolated CPUs

On 7/2/25 18:33, Daniel Wagner wrote:
> When isolcpus=io_queue is enabled, and the last housekeeping CPU for a
> given hctx goes offline, there would be no CPU left to handle I/O. To
> prevent I/O stalls, prevent offlining housekeeping CPUs that are still
> serving isolated CPUs.
> 
> When isolcpus=io_queue is enabled and the last housekeeping CPU
> for a given hctx goes offline, no CPU would be left to handle I/O.
> To prevent I/O stalls, disallow offlining housekeeping CPUs that are
> still serving isolated CPUs.
> 
> Signed-off-by: Daniel Wagner <wagi@...nel.org>
> ---
>   block/blk-mq.c | 42 ++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 42 insertions(+)
> 
Reviewed-by: Hannes Reinecke <hare@...e.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@...e.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich