linux-kernel - Re: [PATCH 01/11] blk-throttle: Limit whole system if root group is configured when on the default hierarchy

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Date:   Wed, 23 Nov 2022 07:11:49 -1000
From:   Tejun Heo <tj@...nel.org>
To:     Kemeng Shi <shikemeng@...wei.com>
Cc:     josef@...icpanda.com, axboe@...nel.dk, cgroups@...r.kernel.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/11] blk-throttle: Limit whole system if root group is
 configured when on the default hierarchy

On Wed, Nov 23, 2022 at 02:03:51PM +0800, Kemeng Shi wrote:
> Quoted from comment in throtl_pd_init: "If on the default hierarchy, we
> switch to properly hierarchical behavior where limits on a given
> throtl_grp are applied to the whole subtree rather than just the group
> itself. e.g. If 16M read_bps limit is set on the root group, the whole
> system can' exceed 16M for the device."

On the default hierarchy (cgroup2), the throttle interface files don't exist
in the root cgroup. In general, cgroup doesn't wanna be in the business of
restricting resources at the system level.

Thanks.

-- 
tejun