Re: [PATCH] ublk_drv: don't forward io commands in reserve order

From: Ming Lei <ming.lei@redhat.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org,
	ZiyangZhang <ZiyangZhang@linux.alibaba.com>,
	Andreas Hindborg <andreas.hindborg@wdc.com>,
	Damien Le Moal <damien.lemoal@opensource.wdc.com>
Subject: Re: [PATCH] ublk_drv: don't forward io commands in reserve order
Date: Thu, 24 Nov 2022 10:00:58 +0800	[thread overview]
Message-ID: <Y37QWsTZj1gW5l6m@T590> (raw)
In-Reply-To: <20221121155645.396272-1-ming.lei@redhat.com>

On Mon, Nov 21, 2022 at 11:56:45PM +0800, Ming Lei wrote:
> Either ublk_can_use_task_work() is true or not, io commands are
> forwarded to ublk server in reverse order, since llist_add() is
> always to add one element to the head of the list.
> 
> Even though block layer doesn't guarantee request dispatch order,
> requests should be sent to hardware in the sequence order generated
> from io scheduler, which usually considers the request's LBA, and
> order is often important for HDD.
> 
> So forward io commands in the sequence made from io scheduler by
> aligning task work with current io_uring command's batch handling,
> and it has been observed that both can get similar performance data
> if IORING_SETUP_COOP_TASKRUN is set from ublk server.
> 
> Reported-by: Andreas Hindborg <andreas.hindborg@wdc.com>
> Cc: Damien Le Moal <damien.lemoal@opensource.wdc.com>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>

Hello Jens,

Can you pick up this patch? 6.1 could be better, but it is fine
for 6.2.

Thanks,
Ming