linux-kernel - Re: [PATCH v9 01/15] asm-generic: add barrier smp_cond_load_relaxed

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Message-ID: <93d1d8f6-702e-811b-2bf6-0e4739e24c1c@gentwo.org>
Date: Tue, 12 Nov 2024 08:50:01 -0800 (PST)
From: "Christoph Lameter (Ampere)" <cl@...two.org>
To: Ankur Arora <ankur.a.arora@...cle.com>
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Subject: Re: [PATCH v9 01/15] asm-generic: add barrier
 smp_cond_load_relaxed_timeout()

On Fri, 8 Nov 2024, Ankur Arora wrote:

> > For power saving most arches have special instructions like ARMS
> > WFE/WFET. These are then causing more accurate wait times than the looping
> > thing?
>
> Definitely true for WFET. The WFE can still overshoot because the
> eventstream has a period of 100us.

We can only use the event stream if we need to wait more than 100us.

The rest of the wait period can be coverd by a busy loop. Thus we are
accurate.