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

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Message-ID: <lv4j25eogwjct5bzy76doh2thucpnqcqlpblbw3etmdrlc5rfq@3svjujqwisii>
Date: Mon, 19 Jan 2026 07:41:20 -0500
From: Aaron Tomlin <atomlin@...mlin.com>
To: Borislav Petkov <bp@...en8.de>
Cc: corbet@....net, anna-maria@...utronix.de, frederic@...nel.org, 
	tglx@...nel.org, mingo@...hat.com, dave.hansen@...ux.intel.com, x86@...nel.org, 
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	fvdl@...gle.com, lirongqing@...du.com, bhelgaas@...gle.com, peterz@...radead.org, 
	brgerst@...il.com, kai.huang@...el.com, benjamin.berg@...el.com, 
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	chjohnst@...il.com, linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/idle: Mark "idle=poll" as deprecated

On Mon, Jan 19, 2026 at 11:21:16AM +0100, Borislav Petkov wrote:
> 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.

Hi Boris,

Thank you for your feedback.

Understood.

I will investigate the possibility of implementing a boot-time parameter
for the PM QoS subsystem to bridge this gap. This would provide the same
immediate enforcement as "idle=poll" while retaining the runtime
flexibility of the QoS framework.


Kind rgards,
-- 
Aaron Tomlin

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