linux-kernel - Re: [PATCH] x86: allow 8 more cpus could be used

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Message-ID: <20090129231259.GB29611@elte.hu>
Date:	Fri, 30 Jan 2009 00:12:59 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Randy Dunlap <randy.dunlap@...cle.com>
Cc:	Yinghai Lu <yinghai@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: allow 8 more cpus could be used


* Randy Dunlap <randy.dunlap@...cle.com> wrote:

> Ingo Molnar wrote:
> > * Yinghai Lu <yinghai@...nel.org> wrote:
> > 
> >> Impact: fix left out MARCO
> >>
> >> X86_PC will be always enabled. so need to check if we have bigsmp 
> >> support built in before cut off more than 8 cpus.
> > 
> > ah, that's a leftover reference to X86_PC. It can now be removed, together 
> > with the Kconfig X86_PC option.
> > 
> >> -#if defined(CONFIG_X86_PC) && defined(CONFIG_X86_32)
> >> +#if defined(CONFIG_X86_PC) && !defined(CONFIG_X86_BIGSMP)
> >>  	if (def_to_bigsmp && nr_cpu_ids > 8) {
> >>  		unsigned int cpu;
> >>  		unsigned nr;
> > 
> > Could you please send a patch that removes both X86_PC and X86_BIGSMP - 
> > and removes the above cutoff code too, so that it will be built-in all the 
> > time?
> 
> and at what cost, please?

the size difference between a bigsmp and a normal-smp x86 defconfig kernel 
is 0.011%. Zero difference on a UP kernel. (And UP is what most of the 
ultra-embedded systems are using)

	Ingo
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