linux-kernel - Re: [PATCH RFC v2 0/6] blk-throttle: support enable and disable during runtime

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Date: Wed, 17 Apr 2024 09:09:07 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Michal Koutný <mkoutny@...e.com>,
 Yu Kuai <yukuai1@...weicloud.com>
Cc: axboe@...nel.dk, chenhuacai@...nel.org, tj@...nel.org,
 josef@...icpanda.com, jhs@...atatu.com, svenjoac@....de, raven@...maw.net,
 pctammela@...atatu.com, qde@...cy.de, zhaotianrui@...ngson.cn,
 linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
 loongarch@...ts.linux.dev, cgroups@...r.kernel.org, yi.zhang@...wei.com,
 yangerkun@...wei.com, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH RFC v2 0/6] blk-throttle: support enable and disable
 during runtime

Hi,

在 2024/04/16 23:56, Michal Koutný 写道:
> On Sat, Apr 06, 2024 at 04:00:53PM +0800, Yu Kuai <yukuai1@...weicloud.com> wrote:
>> I'm planning to support build all blk-throttle polices as kernel module,
> 
> There is only one blk-throttle policy (especially after your removal of
> io.low). Did you mean blkcg policies in general?

Yes, bfq already support that, and others are all rq_qos based, they
will be much easier than blk-throtl.
> 
> The current code is complex because of various lifecycles in
> 	devices x cgroups.
> Turning policies into modules seems to make it
> 	devices x cgroups x policy modules
> .
> 
> Could you please add more info why policies as modules is beneficial,
> how to keep complexity capped?

First of all, users can only load these policies when they need, and
reduce kernel size; Then, when these policies is not loaded, IO fast
path will be slightly shorter, and save some memory overhead for each
disk.

Thanks,
Kuai

> 
> Thanks,
> Michal
>