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

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Message-ID: <20250216190540.254512a5@pumpkin>
Date: Sun, 16 Feb 2025 19:05:40 +0000
From: David Laight <david.laight.linux@...il.com>
To: Qais Yousef <qyousef@...alina.io>
Cc: 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 Mon, 10 Feb 2025 00:19:15 +0000
Qais Yousef <qyousef@...alina.io> wrote:

> The frequency at which TICK happens is very important from scheduler
> perspective. There's a responsiveness trade-of that for interactive
> systems the current default is set too low.

The problem I see is that most people use a kernel from one of the distributions.
So you need to persuade them to change their default.
Change the default 'default' won't necessarily have any effect.

OTOH if you decouple the timer interrupt rate from HZ (or jiffies)
then it becomes possible to boot time (or even run-time) change
the timer interrupt rate.

So it makes much more sense to fix 'jiffies' as a 1ms counter and then
configure the timer interrupt to be a number of ms/jiffies.

This would be similar all the simplifications that came about by making
the high precision timestamps (etc) ns regardless of the actual
resolution on any specific hardware.

	David