linux-kernel - Re: [PATCH] Do not force shutdown/reboot to boot cpu.

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Message-ID: <5165A82E.8000609@zytor.com>
Date:	Wed, 10 Apr 2013 10:58:06 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Ingo Molnar <mingo@...nel.org>
CC:	Russ Anderson <rja@....com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Robin Holt <holt@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Shawn Guo <shawn.guo@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	the arch/x86 maintainers <x86@...nel.org>
Subject: Re: [PATCH] Do not force shutdown/reboot to boot cpu.

On 04/10/2013 09:59 AM, Ingo Molnar wrote:
> 
> 4 minutes bootup is 240 seconds, with 1024 CPUs that's about 240 msecs per CPU.
> 
> That sounds a lot, given that unlike bootup there's not much real work to be done 
> during shutdown - we don't initialize anything, etc.
> 
> Maybe much of those 240 msecs are spent in some stupid udelay loop or so, which 
> could be made parallel?
> 

I wonder if it isn't calling stop_machine() 1024 times, each time
rendezvousing all the still-active CPUs.

	-hpa


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