From: Jan Kara <jack@suse.cz>
To: Bart Van Assche <bvanassche@acm.org>
Cc: Hou Tao <houtao@huaweicloud.com>,
linux-block@vger.kernel.org, Jan Kara <jack@suse.cz>,
Jens Axboe <axboe@kernel.dk>,
cgroups@vger.kernel.org, Tejun Heo <tj@kernel.org>,
Zefan Li <lizefan.x@bytedance.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Jonathan Corbet <corbet@lwn.net>,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
houtao1@huawei.com
Subject: Re: [PATCH] blk-ioprio: Introduce promote-to-rt policy
Date: Wed, 8 Feb 2023 14:43:45 +0100 [thread overview]
Message-ID: <20230208134345.77bdep3kzp52haxu@quack3> (raw)
In-Reply-To: <aedc240d-7c9e-248a-52d2-c9775f3e8ca1@acm.org>
On Fri 03-02-23 11:45:32, Bart Van Assche wrote:
> On 2/2/23 17:48, Hou Tao wrote:
> > I don't get it on how to remove IOPRIO_POL_PROMOTION when calculating the final
> > ioprio for bio. IOPRIO_POL_PROMOTION is not used for IOPRIO_CLASS values but
> > used to determinate on how to calculate the final ioprio for bio: choosing the
> > maximum or minimum between blkcg ioprio and original bio bi_ioprio.
>
> Do the block layer code changes shown below implement the functionality
> that you need?
Just one question guys: So with my a78418e6a04c ("block: Always initialize
bio IO priority on submit") none-to-rt policy became effectively a noop as
Hou properly noticed. Are we aware of any users that were broken by this?
Shouldn't we rather fix the code so that none-to-rt starts to operate
correctly again? Or maybe change the none-to-rt meaning to be actually
promote-to-rt?
I have to admit I'm wondering a bit what was the intended usecase behind
the introduction of none-to-rt policy. Can someone elaborate? promote-to-rt
makes some sense to me - we have a priviledged cgroup we want to provide
low latency access to IO but none-to-rt just does not make much sense to
me...
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2023-02-08 13:45 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-01 4:52 [PATCH] blk-ioprio: Introduce promote-to-rt policy Hou Tao
2023-02-01 9:07 ` Bagas Sanjaya
2023-02-02 10:50 ` Hou Tao
2023-02-01 17:33 ` Bart Van Assche
2023-02-02 11:09 ` Hou Tao
2023-02-02 18:05 ` Bart Van Assche
2023-02-03 1:48 ` Hou Tao
2023-02-03 19:45 ` Bart Van Assche
2023-02-05 7:04 ` Hou Tao
2023-02-08 13:43 ` Jan Kara [this message]
2023-02-08 17:53 ` Bart Van Assche
2023-02-09 8:56 ` Jan Kara
2023-02-09 19:09 ` Bart Van Assche
2023-02-10 10:12 ` Jan Kara
2023-02-13 12:51 ` Hou Tao
2023-02-13 17:10 ` Bart Van Assche
2023-02-14 8:52 ` Jan Kara
2023-02-03 19:51 ` Bart Van Assche
2023-02-05 7:17 ` Hou Tao
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