Messages in this thread | | | From | "Limonciello, Mario" <> | Subject | RE: [PATCH] ACPI: processor_idle: Skip dummy wait for processors based on the Zen microarchitecture | Date | Thu, 22 Sep 2022 18:28:48 +0000 |
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[Public]
> -----Original Message----- > From: Dave Hansen <dave.hansen@intel.com> > Sent: Thursday, September 22, 2022 13:18 > To: Limonciello, Mario <Mario.Limonciello@amd.com>; Nayak, K Prateek > <KPrateek.Nayak@amd.com>; linux-kernel@vger.kernel.org > Cc: rafael@kernel.org; lenb@kernel.org; linux-acpi@vger.kernel.org; linux- > pm@vger.kernel.org; dave.hansen@linux.intel.com; bp@alien8.de; > tglx@linutronix.de; andi@lisas.de; puwen@hygon.cn; peterz@infradead.org; > rui.zhang@intel.com; gpiccoli@igalia.com; daniel.lezcano@linaro.org; > Narayan, Ananth <Ananth.Narayan@amd.com>; Shenoy, Gautham Ranjal > <gautham.shenoy@amd.com>; Ong, Calvin <Calvin.Ong@amd.com>; > stable@vger.kernel.org; regressions@lists.linux.dev > Subject: Re: [PATCH] ACPI: processor_idle: Skip dummy wait for processors > based on the Zen microarchitecture > > On 9/22/22 10:48, Limonciello, Mario wrote: > > > > 2) The title says to limit it to old intel systems, but nothing about this > actually enforces that. > > It actually is limited to all Intel systems, but effectively won't be used on > anything but new > > ones because of intel_idle. > > > > As an idea for #2 you could check for CONFIG_INTEL_IDLE in the Intel case > and > > if it's not defined show a pr_notice_once() type of message trying to tell > people to use > > Intel Idle instead for better performance. > > What does that have to do with *this* patch, though?
It was just a thought triggered by your commit message title.
> > If you've got CONFIG_INTEL_IDLE disabled, you'll be slow before this > patch. You'll also be slow after this patch. It's entirely orthogonal. >
Yeah it's orthogonal, but with this discussion happening and the code is changing /anyway/ then a pr_notice_once() seemed like a nice way to guide people towards intel_idle at the same time so they didn't trip into the same problem AMD systems do today.
> I can add a "Practically" to the subject so folks don't confuse it with > some hard limit that is being enforced: > > ACPI: processor idle: Practically limit "Dummy wait" workaround to > old > Intel systems
That works.
> > BTW, is there seriously a strong technical reason that AMD systems are > still using this code? Or is it pure inertia?
Maybe a better question for Ananth and Prateek to comment on.
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