linux-kernel - Re: [PATCH] Kconfig.hz: Change default HZ to 1000

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Message-ID: <Z7rTNxHcXWizV3lq@gpd3>
Date: Sun, 23 Feb 2025 08:50:15 +0100
From: Andrea Righi <arighi@...dia.com>
To: Joel Fernandes <joelagnelf@...dia.com>
Cc: Qais Yousef <qyousef@...alina.io>, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	John Stultz <jstultz@...gle.com>,
	Saravana Kannan <saravanak@...gle.com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Frederic Weisbecker <frederic@...nel.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Kconfig.hz: Change default HZ to 1000

On Wed, Feb 12, 2025 at 09:50:54AM -0500, Joel Fernandes wrote:
> On Mon, Feb 10, 2025 at 12:19:15AM +0000, Qais Yousef wrote:
...
> > I believe HZ_250 was the default as a trade-off for battery power
> > devices that might not be happy with frequent TICKS potentially draining
> > the battery unnecessarily. But to my understanding the current state of
> 
> Actually, on x86, me and Steve did some debug on Chromebooks and we found
> that HZ_250 actually increased power versus higher HZ. This was because
> cpuidle governor changes C states on the tick, and by making it less
> frequent, the CPU could be in a shallow C state for longer.

FWIW, I found the same about power consumption when we decided to switch to
CONFIG_HZ=1000 in the Ubuntu kernel:
https://discourse.ubuntu.com/t/enable-low-latency-features-in-the-generic-ubuntu-kernel-for-24-04/42255

-Andrea