From: Ming Lei <ming.lei@redhat.com>
To: Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>
Cc: linux-block@vger.kernel.org,
Lai Jiangshan <jiangshanlai@gmail.com>,
"Paul E . McKenney" <paulmck@kernel.org>,
Josh Triplett <josh@joshtriplett.org>,
Sagi Grimberg <sagi@grimberg.me>,
Bart Van Assche <bvanassche@acm.org>
Subject: Re: [RFC PATCH] blk-mq: implement queue quiesce via percpu_ref for BLK_MQ_F_BLOCKING
Date: Wed, 29 Jul 2020 18:28:56 +0800 [thread overview]
Message-ID: <20200729102856.GA1563056@T590> (raw)
In-Reply-To: <20200728134938.1505467-1-ming.lei@redhat.com>
On Tue, Jul 28, 2020 at 09:49:38PM +0800, Ming Lei wrote:
> In case of BLK_MQ_F_BLOCKING, blk-mq uses SRCU to mark read critical
> section during dispatching request, then request queue quiesce is based on
> SRCU. What we want to get is low cost added in fast path.
>
> However, from srcu_read_lock/srcu_read_unlock implementation, not see
> it is quicker than percpu refcount, so use percpu_ref to implement
> queue quiesce. This usage is cleaner and simpler & enough for implementing
> queue quiesce. The main requirement is to make sure all read sections to observe
> QUEUE_FLAG_QUIESCED once blk_mq_quiesce_queue() returns.
>
> Also it becomes much easier to add interface of async queue quiesce.
BTW, no obvious IOPS difference is observed with this patch applied when running
io on null_blk(blocking, submit_queues=32) in one dual-socket, 32cores system.
Thanks,
Ming
next prev parent reply other threads:[~2020-07-29 10:29 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-28 13:49 [RFC PATCH] blk-mq: implement queue quiesce via percpu_ref for BLK_MQ_F_BLOCKING Ming Lei
2020-07-29 10:28 ` Ming Lei [this message]
2020-07-29 15:42 ` Sagi Grimberg
2020-07-29 15:49 ` Ming Lei
2020-07-29 22:37 ` Sagi Grimberg
2020-07-30 14:53 ` Ming Lei
2020-07-30 16:10 ` Sagi Grimberg
2020-07-30 18:18 ` Keith Busch
2020-07-30 18:23 ` Sagi Grimberg
2020-07-30 19:27 ` Keith Busch
2020-07-30 19:53 ` Jens Axboe
2020-07-30 21:03 ` Sagi Grimberg
2020-07-31 0:33 ` Ming Lei
2020-07-31 0:24 ` Ming Lei
2020-07-31 0:28 ` Ming Lei
2020-07-29 11:20 ` Johannes Thumshirn
2020-07-29 16:12 ` Keith Busch
2020-07-29 22:16 ` Ming Lei
2020-07-29 22:42 ` Sagi Grimberg
2020-07-30 15:05 ` Ming Lei
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