From: Keith Busch <kbusch@kernel.org>
To: Mohamed Khalfella <mkhalfella@purestorage.com>
Cc: Bart Van Assche <bvanassche@acm.org>,
Chaitanya Kulkarni <kch@nvidia.com>,
Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
Sagi Grimberg <sagi@grimberg.me>,
Casey Chen <cachen@purestorage.com>,
Yuanyuan Zhong <yzhong@purestorage.com>,
Hannes Reinecke <hare@suse.de>, Ming Lei <ming.lei@redhat.com>,
Waiman Long <llong@redhat.com>, Hillf Danton <hdanton@sina.com>,
linux-nvme@lists.infradead.org, linux-block@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] block: Use RCU in blk_mq_[un]quiesce_tagset() instead of set->tag_list_lock
Date: Fri, 5 Dec 2025 11:11:23 -0700 [thread overview]
Message-ID: <aTMgS0njg-R-T0pT@kbusch-mbp> (raw)
In-Reply-To: <20251205163926.GI2376676-mkhalfella@purestorage.com>
On Fri, Dec 05, 2025 at 08:39:26AM -0800, Mohamed Khalfella wrote:
> Why sychronize_rcu() is intolerable in this blk_mq_del_queue_tag_set()?
> This code is not performance sensitive, right?
synchronize_rcu() gets expensive on servers with many CPUs. While this
is not a fast path, I think adding it here would still be harmful, if
only just to testing when devices are frequently created and deleted.
> Looking at the code again, I _think_ synchronize_rcu() along with
> INIT_LIST_HEAD(&q->tag_set_list) can be deleted. I do not see usecase
> where "q" is re-added to a tagset after it is deleted from one.
> Also, "q" is freed in blk_free_queue() after end of RCU grace period.
I think you could skip the synchronize since the queue's memory free is
done in blk_free_queue_rcu from a call_rcu() callback.
next prev parent reply other threads:[~2025-12-05 18:11 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-04 18:11 [PATCH 0/1] Use RCU in blk_mq_[un]quiesce_tagset() instead of set->tag_list_lock Mohamed Khalfella
2025-12-04 18:11 ` [PATCH 1/1] block: " Mohamed Khalfella
2025-12-04 18:22 ` Bart Van Assche
2025-12-04 18:42 ` Mohamed Khalfella
2025-12-04 19:06 ` Bart Van Assche
2025-12-04 19:15 ` Mohamed Khalfella
2025-12-04 19:31 ` Bart Van Assche
2025-12-04 19:57 ` Mohamed Khalfella
2025-12-04 20:24 ` Bart Van Assche
2025-12-04 21:26 ` Keith Busch
2025-12-04 23:22 ` Bart Van Assche
2025-12-05 1:32 ` Keith Busch
2025-12-05 2:52 ` Bart Van Assche
2025-12-05 16:39 ` Mohamed Khalfella
2025-12-05 18:11 ` Keith Busch [this message]
2025-12-08 19:22 ` Bart Van Assche
2025-12-04 19:02 ` Mohamed Khalfella
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=aTMgS0njg-R-T0pT@kbusch-mbp \
--to=kbusch@kernel.org \
--cc=axboe@kernel.dk \
--cc=bvanassche@acm.org \
--cc=cachen@purestorage.com \
--cc=hare@suse.de \
--cc=hch@lst.de \
--cc=hdanton@sina.com \
--cc=kch@nvidia.com \
--cc=linux-block@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-nvme@lists.infradead.org \
--cc=llong@redhat.com \
--cc=ming.lei@redhat.com \
--cc=mkhalfella@purestorage.com \
--cc=sagi@grimberg.me \
--cc=yzhong@purestorage.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.