linux-kernel - Re: [PATCH v2 2/2] sched

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Date: Fri, 21 Jun 2024 12:39:13 -1000
From: Tejun Heo <tj@...nel.org>
To: rafael@...nel.org, viresh.kumar@...aro.org
Cc: linux-pm@...r.kernel.org, void@...ifault.com,
	linux-kernel@...r.kernel.org, kernel-team@...a.com,
	mingo@...hat.com, peterz@...radead.org,
	David Vernet <dvernet@...a.com>,
	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH v2 2/2] sched_ext: Add cpuperf support

On Wed, Jun 19, 2024 at 09:51:39AM -1000, Tejun Heo wrote:
> sched_ext currently does not integrate with schedutil. When schedutil is the
> governor, frequencies are left unregulated and usually get stuck close to
> the highest performance level from running RT tasks.
> 
> Add CPU performance monitoring and scaling support by integrating into
> schedutil. The following kfuncs are added:
> 
> - scx_bpf_cpuperf_cap(): Query the relative performance capacity of
>   different CPUs in the system.
> 
> - scx_bpf_cpuperf_cur(): Query the current performance level of a CPU
>   relative to its max performance.
> 
> - scx_bpf_cpuperf_set(): Set the current target performance level of a CPU.
> 
> This gives direct control over CPU performance setting to the BPF scheduler.
> The only changes on the schedutil side are accounting for the utilization
> factor from sched_ext and disabling frequency holding heuristics as it may
> not apply well to sched_ext schedulers which may have a lot weaker
> connection between tasks and their current / last CPU.
> 
> With cpuperf support added, there is no reason to block uclamp. Enable while
> at it.
> 
> A toy implementation of cpuperf is added to scx_qmap as a demonstration of
> the feature.
> 
> v2: Ignore cpu_util_cfs_boost() when scx_switched_all() in sugov_get_util()
>     to avoid factoring in stale util metric. (Christian)
> 
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Reviewed-by: David Vernet <dvernet@...a.com>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Cc: Viresh Kumar <viresh.kumar@...aro.org>
> Cc: Christian Loehle <christian.loehle@....com>

Applied to sched_ext/for-6.11.

Thanks.

-- 
tejun