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Date: Mon, 3 Nov 2014 19:54:48 +0800
Message-ID: <CACVXFVMrj_pnYYKzv7zBqQQFiKoE+gVjhNB6evqGUk7wic-i-Q@mail.gmail.com>
Subject: Re: [PATCH 2/2] blk-mq: allow direct dispatch to a driver specific workqueue
From: Ming Lei <tom.leiming@gmail.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@fb.com>, Richard Weinberger <richard@nod.at>,
        ceph-devel@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Sender: linux-kernel-owner@vger.kernel.org

On Mon, Nov 3, 2014 at 6:10 PM, Christoph Hellwig <hch@lst.de> wrote:
> On Mon, Nov 03, 2014 at 04:40:47PM +0800, Ming Lei wrote:
>> The above two aren't enough because the big problem is that
>> drivers need a per-request work structure instead of 'hctx->run_work',
>> otherwise there are at most NR_CPUS concurrent submissions.
>>
>> So the per-request work structure should be exposed to blk-mq
>> too for the kind of usage, such as .blk_mq_req_work(req) callback
>> in case of BLK_MQ_F_WORKQUEUE.
>
> Hmm.  Maybe a better option is to just add a flag to never defer
> ->queue_rq to a workqueue and let drivers handle the it?

That should work, but might lose potential merge benefit of defer.


Thanks,
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