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From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Sagi Grimberg <sagi@grimberg.me>, Jens Axboe <axboe@kernel.dk>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	linux-nvme@lists.infradead.org, linux-block@vger.kernel.org,
	Chao Leng <lengchao@huawei.com>, Keith Busch <kbusch@kernel.org>,
	Ming Lin <mlin@kernel.org>, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v5 1/2] blk-mq: add tagset quiesce interface
Date: Tue, 28 Jul 2020 12:57:41 +0200	[thread overview]
Message-ID: <20200728105741.GA29763@lst.de> (raw)
In-Reply-To: <20200728101042.GA1336890@T590>

On Tue, Jul 28, 2020 at 06:10:42PM +0800, Ming Lei wrote:
> +	struct blk_mq_hw_ctx *hctx = (void *)srcu -
> +		sizeof(struct blk_mq_hw_ctx);

I think this should use container_of.

> +{
> +	struct blk_mq_hw_ctx *hctx;
> +	unsigned int i;
> +
> +	blk_mq_quiesce_queue_nowait(q);
> +
> +	queue_for_each_hw_ctx(q, hctx, i) {
> +		WARN_ON_ONCE(!(hctx->flags & BLK_MQ_F_BLOCKING));
> +		init_rcu_head(&hctx->srcu->head);

We only need to initialize the rcu head once when we allocate the hctx.

> +	mutex_lock(&set->tag_list_lock);
> +	if (set->flags & BLK_MQ_F_BLOCKING) {
> +		int count = 0;
> +
> +		list_for_each_entry(q, &set->tag_list, tag_set_list)
> +			count++;
> +
> +		atomic_set(&set->quiesce_count, count);
> +		init_completion(&set->quiesce_completion);
> +
> +		list_for_each_entry(q, &set->tag_list, tag_set_list)
> +			blk_mq_quiesce_blocking_queue_async(q);
> +		wait_for_completion(&set->quiesce_completion);
> +	} else {
> +		list_for_each_entry(q, &set->tag_list, tag_set_list)
> +			blk_mq_quiesce_queue_nowait(q);
> +		synchronize_rcu();
> +	}
> +	mutex_unlock(&set->tag_list_lock);

It would be great to do the wait_for_completion and synchronize_rcu
outside the lock.  Also I think the blocking case probably wants to be
split into a separate little helper.

WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>, Sagi Grimberg <sagi@grimberg.me>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	linux-nvme@lists.infradead.org, linux-block@vger.kernel.org,
	Chao Leng <lengchao@huawei.com>, Keith Busch <kbusch@kernel.org>,
	Ming Lin <mlin@kernel.org>, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v5 1/2] blk-mq: add tagset quiesce interface
Date: Tue, 28 Jul 2020 12:57:41 +0200	[thread overview]
Message-ID: <20200728105741.GA29763@lst.de> (raw)
In-Reply-To: <20200728101042.GA1336890@T590>

On Tue, Jul 28, 2020 at 06:10:42PM +0800, Ming Lei wrote:
> +	struct blk_mq_hw_ctx *hctx = (void *)srcu -
> +		sizeof(struct blk_mq_hw_ctx);

I think this should use container_of.

> +{
> +	struct blk_mq_hw_ctx *hctx;
> +	unsigned int i;
> +
> +	blk_mq_quiesce_queue_nowait(q);
> +
> +	queue_for_each_hw_ctx(q, hctx, i) {
> +		WARN_ON_ONCE(!(hctx->flags & BLK_MQ_F_BLOCKING));
> +		init_rcu_head(&hctx->srcu->head);

We only need to initialize the rcu head once when we allocate the hctx.

> +	mutex_lock(&set->tag_list_lock);
> +	if (set->flags & BLK_MQ_F_BLOCKING) {
> +		int count = 0;
> +
> +		list_for_each_entry(q, &set->tag_list, tag_set_list)
> +			count++;
> +
> +		atomic_set(&set->quiesce_count, count);
> +		init_completion(&set->quiesce_completion);
> +
> +		list_for_each_entry(q, &set->tag_list, tag_set_list)
> +			blk_mq_quiesce_blocking_queue_async(q);
> +		wait_for_completion(&set->quiesce_completion);
> +	} else {
> +		list_for_each_entry(q, &set->tag_list, tag_set_list)
> +			blk_mq_quiesce_queue_nowait(q);
> +		synchronize_rcu();
> +	}
> +	mutex_unlock(&set->tag_list_lock);

It would be great to do the wait_for_completion and synchronize_rcu
outside the lock.  Also I think the blocking case probably wants to be
split into a separate little helper.

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  reply	other threads:[~2020-07-28 10:57 UTC|newest]

Thread overview: 80+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-27 23:10 [PATCH v5 0/2] improve nvme quiesce time for large amount of namespaces Sagi Grimberg
2020-07-27 23:10 ` Sagi Grimberg
2020-07-27 23:10 ` [PATCH v5 1/2] blk-mq: add tagset quiesce interface Sagi Grimberg
2020-07-27 23:10   ` Sagi Grimberg
2020-07-27 23:32   ` Keith Busch
2020-07-27 23:32     ` Keith Busch
2020-07-28  0:12     ` Sagi Grimberg
2020-07-28  0:12       ` Sagi Grimberg
2020-07-28  1:40   ` Ming Lei
2020-07-28  1:40     ` Ming Lei
2020-07-28  1:51     ` Jens Axboe
2020-07-28  1:51       ` Jens Axboe
2020-07-28  2:17       ` Ming Lei
2020-07-28  2:17         ` Ming Lei
2020-07-28  2:23         ` Jens Axboe
2020-07-28  2:23           ` Jens Axboe
2020-07-28  2:28           ` Ming Lei
2020-07-28  2:28             ` Ming Lei
2020-07-28  2:32             ` Jens Axboe
2020-07-28  2:32               ` Jens Axboe
2020-07-28  3:29               ` Sagi Grimberg
2020-07-28  3:29                 ` Sagi Grimberg
2020-07-28  3:25     ` Sagi Grimberg
2020-07-28  3:25       ` Sagi Grimberg
2020-07-28  7:18   ` Christoph Hellwig
2020-07-28  7:18     ` Christoph Hellwig
2020-07-28  7:48     ` Sagi Grimberg
2020-07-28  7:48       ` Sagi Grimberg
2020-07-28  9:16     ` Ming Lei
2020-07-28  9:16       ` Ming Lei
2020-07-28  9:24       ` Sagi Grimberg
2020-07-28  9:24         ` Sagi Grimberg
2020-07-28  9:33         ` Ming Lei
2020-07-28  9:33           ` Ming Lei
2020-07-28  9:37           ` Sagi Grimberg
2020-07-28  9:37             ` Sagi Grimberg
2020-07-28  9:43             ` Sagi Grimberg
2020-07-28  9:43               ` Sagi Grimberg
2020-07-28 10:10               ` Ming Lei
2020-07-28 10:10                 ` Ming Lei
2020-07-28 10:57                 ` Christoph Hellwig [this message]
2020-07-28 10:57                   ` Christoph Hellwig
2020-07-28 14:13                 ` Paul E. McKenney
2020-07-28 14:13                   ` Paul E. McKenney
2020-07-28 10:58             ` Christoph Hellwig
2020-07-28 10:58               ` Christoph Hellwig
2020-07-28 16:25               ` Sagi Grimberg
2020-07-28 16:25                 ` Sagi Grimberg
2020-07-28 13:54         ` Paul E. McKenney
2020-07-28 13:54           ` Paul E. McKenney
2020-07-28 23:46           ` Sagi Grimberg
2020-07-28 23:46             ` Sagi Grimberg
2020-07-29  0:31             ` Paul E. McKenney
2020-07-29  0:31               ` Paul E. McKenney
2020-07-29  0:43               ` Sagi Grimberg
2020-07-29  0:43                 ` Sagi Grimberg
2020-07-29  0:59                 ` Keith Busch
2020-07-29  0:59                   ` Keith Busch
2020-07-29  4:39                   ` Sagi Grimberg
2020-07-29  4:39                     ` Sagi Grimberg
2020-08-07  9:04                     ` Chao Leng
2020-08-07  9:04                       ` Chao Leng
2020-08-07  9:24                       ` Ming Lei
2020-08-07  9:24                         ` Ming Lei
2020-08-07  9:35                         ` Chao Leng
2020-08-07  9:35                           ` Chao Leng
2020-07-29  4:10                 ` Paul E. McKenney
2020-07-29  4:10                   ` Paul E. McKenney
2020-07-29  4:37                   ` Sagi Grimberg
2020-07-29  4:37                     ` Sagi Grimberg
2020-07-27 23:10 ` [PATCH v5 2/2] nvme: use blk_mq_[un]quiesce_tagset Sagi Grimberg
2020-07-27 23:10   ` Sagi Grimberg
2020-07-28  0:54   ` Sagi Grimberg
2020-07-28  0:54     ` Sagi Grimberg
2020-07-28  3:21     ` Chao Leng
2020-07-28  3:21       ` Chao Leng
2020-07-28  3:34       ` Sagi Grimberg
2020-07-28  3:34         ` Sagi Grimberg
2020-07-28  3:51         ` Chao Leng
2020-07-28  3:51           ` Chao Leng

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