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Subject: Re: [PATCH] Adding multiple workers to the loop device.
To:     "muraliraja.muniraju" <muraliraja.muniraju@rubrik.com>
Cc:     linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20200121192540.51642-1-muraliraja.muniraju@rubrik.com>
From:   Jens Axboe <axboe@kernel.dk>
Message-ID: <88d16046-f9aa-d5e8-1b1c-7c3ff9516290@kernel.dk>
Date:   Thu, 23 Jan 2020 11:59:10 -0700
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On 1/21/20 12:25 PM, muraliraja.muniraju wrote:
> Current loop device implementation has a single kthread worker and
> drains one request at a time to completion. If the underneath device is
> slow then this reduces the concurrency significantly. To help in these
> cases, adding multiple loop workers increases the concurrency. Also to
> retain the old behaviour the default number of loop workers is 1 and can
> be tuned via the ioctl.

Have you considered using blk-mq for this? Right now loop just does
some basic checks and then queues for a thread. If you bump nr_hw_queues
up (provide a parameter for that) and set BLK_MQ_F_BLOCKING in the
tag flags, then that might be a more viable approach for handling this.

-- 
Jens Axboe