linux-kernel - Re: [PATCH] x86/idle: Mark "idle=poll" as deprecated

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Message-ID: <20260119102116.GAaW4FnNBECNPFzAW3@fat_crate.local>
Date: Mon, 19 Jan 2026 11:21:16 +0100
From: Borislav Petkov <bp@...en8.de>
To: Aaron Tomlin <atomlin@...mlin.com>
Cc: corbet@....net, anna-maria@...utronix.de, frederic@...nel.org,
	tglx@...nel.org, mingo@...hat.com, dave.hansen@...ux.intel.com,
	x86@...nel.org, hpa@...or.com, akpm@...ux-foundation.org,
	pawan.kumar.gupta@...ux.intel.com, feng.tang@...ux.alibaba.com,
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	brgerst@...il.com, kai.huang@...el.com, benjamin.berg@...el.com,
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	sean@...e.io, mproche@...il.com, chjohnst@...il.com,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/idle: Mark "idle=poll" as deprecated

On Sun, Jan 18, 2026 at 06:10:09PM -0500, Aaron Tomlin wrote:
> The "idle=poll" boot parameter is a blunt instrument that forces all
> CPUs in the system into a continuous "polling" state. While effective
> at eliminating wake-up latency, this global override is architecturally
> obsolete and inefficient on modern multicore systems.

Nope.

It is still very useful when you want to stop the machine from entering sleep
states.

> By writing special value "n/a" to the per-CPU sysfs node
> /sys/devices/system/cpu/cpuN/power/pm_qos_resume_latency_us, userspace
> can force a specific CPU to poll without imposing this cost globally.

You can't do that on the kernel command line and thus prevent entering sleep
states from the get-go.

So no, it ain't broke so no need to fix it.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette