From: Jens Axboe <axboe@kernel.dk>
To: Jeff Moyer <jmoyer@redhat.com>
Cc: Ming Lei <ming.lei@canonical.com>,
Jason Luo <zhangqing.luo@oracle.com>,
linux-kernel@vger.kernel.org
Subject: Re: [patch, v3] blk-mq: avoid excessive boot delays with large lun counts
Date: Tue, 3 Nov 2015 08:46:04 -0700 [thread overview]
Message-ID: <5638D6BC.4050607@kernel.dk> (raw)
In-Reply-To: <x4937wn3xd5.fsf@segfault.boston.devel.redhat.com>
On 11/03/2015 08:40 AM, Jeff Moyer wrote:
> Hi,
>
> Zhangqing Luo reported long boot times on a system with thousands of
> LUNs when scsi-mq was enabled. He narrowed the problem down to
> blk_mq_add_queue_tag_set, where every queue is frozen in order to set
> the BLK_MQ_F_TAG_SHARED flag. Each added device will freeze all queues
> added before it in sequence, which involves waiting for an RCU grace
> period for each one. We don't need to do this. After the second queue
> is added, only new queues need to be initialized with the shared tag.
> We can do that by percolating the flag up to the blk_mq_tag_set, and
> updating the newly added queue's hctxs if the flag is set.
>
> This problem was introduced by commit 0d2602ca30e41 (blk-mq: improve
> support for shared tags maps).
Applied, thanks Jeff and Ming.
--
Jens Axboe
prev parent reply other threads:[~2015-11-03 15:46 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-03 15:40 [patch, v3] blk-mq: avoid excessive boot delays with large lun counts Jeff Moyer
2015-11-03 15:46 ` Jens Axboe [this message]
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