linux-kernel - Re: [PATCH v7 0/2] Improve VM CPUfreq and task placement behavior

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Message-ID: <20241001092544.2tlydouyyc7jwuja@vireshk-i7>
Date: Tue, 1 Oct 2024 14:55:44 +0530
From: Viresh Kumar <viresh.kumar@...aro.org>
To: David Dai <davidai@...gle.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Sudeep Holla <sudeep.holla@....com>,
	Saravana Kannan <saravanak@...gle.com>,
	Quentin Perret <qperret@...gle.com>,
	Masami Hiramatsu <mhiramat@...gle.com>,
	Will Deacon <will@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Marc Zyngier <maz@...nel.org>,
	Oliver Upton <oliver.upton@...ux.dev>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Pavan Kondeti <quic_pkondeti@...cinc.com>,
	Gupta Pankaj <pankaj.gupta@....com>, Mel Gorman <mgorman@...e.de>,
	kernel-team@...roid.com, linux-pm@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 0/2] Improve VM CPUfreq and task placement behavior

On 18-09-24, 17:08, David Dai wrote:
> Hi,
> 
> This patch series is a continuation of the talk Saravana gave at LPC 2022
> titled "CPUfreq/sched and VM guest workload problems" [1][2][3]. The gist
> of the talk is that workloads running in a guest VM get terrible task
> placement and CPUfreq behavior when compared to running the same workload
> in the host. Effectively, no EAS(Energy Aware Scheduling) for threads
> inside VMs. This would make power and performance terrible just by running
> the workload in a VM even if we assume there is zero virtualization
> overhead.

> David Dai (2):
>   dt-bindings: cpufreq: add virtual cpufreq device
>   cpufreq: add virtual-cpufreq driver
> 
>  .../cpufreq/qemu,virtual-cpufreq.yaml         |  48 +++
>  drivers/cpufreq/Kconfig                       |  14 +
>  drivers/cpufreq/Makefile                      |   1 +
>  drivers/cpufreq/virtual-cpufreq.c             | 333 ++++++++++++++++++
>  include/linux/arch_topology.h                 |   1 +
>  5 files changed, 397 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/cpufreq/qemu,virtual-cpufreq.yaml
>  create mode 100644 drivers/cpufreq/virtual-cpufreq.c

LGTM.

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

-- 
viresh