linux-kernel - Re: [PATCH 0/1] speeding up cpu

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Message-ID: <CAJvTdKnYbJbun_UJXbGgKuh7DEBXoQdD6Unbm=Jopuw_C_U4ng@mail.gmail.com>
Date:	Fri, 1 May 2015 14:42:39 -0700
From:	Len Brown <lenb@...nel.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	X86 ML <x86@...nel.org>, Linux PM list <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Borislav Petkov <bp@...en8.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH 0/1] speeding up cpu_up()

On Mon, Apr 20, 2015 at 12:15 AM, Ingo Molnar <mingo@...nel.org> wrote:

> So instead of playing games with an ancient delay, I'd suggest we
> install the 10 msec INIT assertion wait as a platform quirk instead,
> and activate it for all CPUs/systems that we think might need it, with
> a sufficiently robust and future-proof quirk cutoff condition.
>
> New systems won't have the quirk active and thus won't have to have
> this delay configurable either.

Okay, at this time, I think the quirk would apply to:

1. Intel family 5 (original pentium) -- some may actually need the quirk
2. Intel family F (pentium4) -- mostly b/c I don't want to bother
finding/testing p4
3. All AMD (happy to narrow down, if somebody can speak for AMD)

I'd keep the cmdline override, in case we break something,
or somebody wants to optimize/test.  (Though I'll update units to
usec, rather than msec.,
so we can go below 1ms without going to 0)
I don't think we need the config option, just a #define to document the quirk.

What do you think?

Len Brown, Intel Open Source Technology Center
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