linux-kernel - Re: [PATCH -next v3] sched: Dec cfs_bandwidth_used in destroy_cfs

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Message-ID: <20210716135353.zcuth5cqzuuajc3u@oracle.com>
Date:   Fri, 16 Jul 2021 09:53:53 -0400
From:   Daniel Jordan <daniel.m.jordan@...cle.com>
To:     Zhang Qiao <zhangqiao22@...wei.com>
Cc:     juri.lelli@...hat.com, linux-kernel@...r.kernel.org,
        mingo@...hat.com, peterz@...radead.org, pjt@...gle.com,
        vincent.guittot@...aro.org
Subject: Re: [PATCH -next v3] sched: Dec cfs_bandwidth_used in
 destroy_cfs_bandwidth()

On Fri, Jul 16, 2021 at 10:27:56AM +0800, Zhang Qiao wrote:
> cfs_bandwidth_used is a static_key to control cfs bandwidth
> feature. When adding a cfs_bandwidth group, we need increase
> the key, and decrease it when removing. But currently when we
> remove a cfs bandwidth group, we don't decrease the key and
> this switch will always be on even if there is no cfs bandwidth
> group in the system.
> 
> Fix the problem as two steps:
> 1.Rename cfs_bandwidth_usage_{dec, inc}() to
> cfs_bandwidth_usage_{dec,inc}_cpuslocked() and its caller need to
> hold the hotplug lock.
> 2.Add cfs_bandwidth_usage_dec() and its caller don't need
> to hold the hotplug lock. And when removing a cfs bandwidth group,
> we decrease cfs_bandwidth_used by calling cfs_bandwidth_usage_dec().
> 
> Fixes: 56f570e512ee ("sched: use jump labels to reduce overhead when bandwidth control is inactive")
> Signed-off-by: Zhang Qiao <zhangqiao22@...wei.com>

Reviewed-by: Daniel Jordan <daniel.m.jordan@...cle.com>