linux-kernel - Re: [PATCH v6 02/10] cpuidle: rename ARCH_HAS_CPU_RELAX to ARCH_HAS_OPTIMIZED

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Message-ID: <43b24caf-2ade-e229-21f4-8c01a47f37ed@gentwo.org>
Date: Mon, 5 Aug 2024 16:09:58 -0700 (PDT)
From: "Christoph Lameter (Ampere)" <cl@...two.org>
To: Ankur Arora <ankur.a.arora@...cle.com>
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Subject: Re: [PATCH v6 02/10] cpuidle: rename ARCH_HAS_CPU_RELAX to
 ARCH_HAS_OPTIMIZED_POLL

On Fri, 26 Jul 2024, Ankur Arora wrote:

> However, recent changes in poll_idle() mean that a higher level
> primitive -- smp_cond_load_relaxed() is used for polling. This would
> in-turn use cpu_relax() or an architecture specific implementation.


Maybe explain here that smp_cond_load_relaxed will potentially wait for 
important events such as a cacheline changing. Thereby making the busy 
poll unnecessary and optimizing power use.