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

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Date:	Mon, 20 Apr 2015 09:15:56 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Len Brown <lenb@...nel.org>
Cc:	x86@...nel.org, linux-pm@...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()


* Len Brown <lenb@...nel.org> wrote:

> The following patch...
> 
> [PATCH 1/1] x86: replace cpu_up hard-coded mdelay with variable
> 
> enables reducing cpu_up() time by 10ms on modern systems.
> 
> This means that for every processor in the system,
> boot-time and resume-time can be reduced by 10ms per-processor.
> 
> Once this patch is accepted, I'll send a subsequent patch
> to update the default delay, as appropriate.
> 
> thanks,
> Len Brown, Intel Open Source Technology Center

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.

Thanks,

	Ingo
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