From: Hou Tao <houtao@huaweicloud.com>
To: Bart Van Assche <bvanassche@acm.org>, linux-block@vger.kernel.org
Cc: 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: Thu, 2 Feb 2023 19:09:24 +0800 [thread overview]
Message-ID: <4f7dcb3e-2d5a-cae3-0e1c-a82bcc3d2217@huaweicloud.com> (raw)
In-Reply-To: <8c068af3-7199-11cf-5c69-a523c7c22d9a@acm.org>
Hi,
On 2/2/2023 1:33 AM, Bart Van Assche wrote:
> On 1/31/23 20:52, Hou Tao wrote:
>> /**
>> * enum prio_policy - I/O priority class policy.
>> * @POLICY_NO_CHANGE: (default) do not modify the I/O priority class.
>> @@ -27,21 +34,30 @@
>> * @POLICY_RESTRICT_TO_BE: modify IOPRIO_CLASS_NONE and IOPRIO_CLASS_RT into
>> * IOPRIO_CLASS_BE.
>> * @POLICY_ALL_TO_IDLE: change the I/O priority class into IOPRIO_CLASS_IDLE.
>> - *
>> + * @POLICY_PROMOTE_TO_RT: modify IOPRIO_CLASS_NONE and IOPRIO_CLASS_BE into
>> + * IOPRIO_CLASS_RT.
>> * See also <linux/ioprio.h>.
>> */
>> enum prio_policy {
>> - POLICY_NO_CHANGE = 0,
>> - POLICY_NONE_TO_RT = 1,
>> - POLICY_RESTRICT_TO_BE = 2,
>> - POLICY_ALL_TO_IDLE = 3,
>> + POLICY_NO_CHANGE = IOPRIO_CLASS_NONE,
>> + POLICY_NONE_TO_RT = IOPRIO_CLASS_RT,
>> + POLICY_RESTRICT_TO_BE = IOPRIO_CLASS_BE,
>> + POLICY_ALL_TO_IDLE = IOPRIO_CLASS_IDLE,
>> + POLICY_PROMOTE_TO_RT = IOPRIO_CLASS_RT | IOPRIO_POL_PROMOTION,
>> +};
>
> The above change complicates the ioprio code. Additionally, I'm concerned that
> it makes the ioprio code slower. Has it been considered to keep the numerical
> values for the existing policies, to assign the number 4 to
> POLICY_PROMOTE_TO_RT and to use a lookup-array in blkcg_set_ioprio() to
> convert the policy number into an IOPRIO_CLASS value?
For the slowness, do you meaning the extra dereference of blkcg->ioprio->policy
when policy is no-change or the handle of IOPRIO_POL_PROMOTION in
blkcg_set_ioprio()? It seems other functions (e.g., ioprio_show_prio_policy()
and ioprio_set_prio_policy()) are not on the hot path. Using a lookup array in
blkcg_set_ioprio() to do the conversion will also be OK, although it will
introduce an extra lookup each time when policy is not no-change. I don't have
strong preference. If you are OK with lookup array in blkcg_set_ioprio(), will
do it in v2.
>
> Thanks,
>
> Bart.
>
>
> .
next prev parent reply other threads:[~2023-02-02 11:10 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 [this message]
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
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4f7dcb3e-2d5a-cae3-0e1c-a82bcc3d2217@huaweicloud.com \
--to=houtao@huaweicloud.com \
--cc=axboe@kernel.dk \
--cc=bvanassche@acm.org \
--cc=cgroups@vger.kernel.org \
--cc=corbet@lwn.net \
--cc=hannes@cmpxchg.org \
--cc=houtao1@huawei.com \
--cc=jack@suse.cz \
--cc=linux-block@vger.kernel.org \
--cc=linux-doc@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=lizefan.x@bytedance.com \
--cc=tj@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).