linux-kernel - Re: [patch] Mark rdtsc as sync only for netburst, not for core2

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Date:	Wed, 29 Nov 2006 17:04:59 +0800
From:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
To:	Nick Piggin <nickpiggin@...oo.com.au>
Cc:	Arjan van de Ven <arjan@...ux.intel.com>, Andi Kleen <ak@...e.de>,
	linux-kernel@...r.kernel.org, akpm@...l.org
Subject: Re: [patch] Mark rdtsc as sync only for netburst, not for core2

On Wed, 2006-11-29 at 19:05 +1100, Nick Piggin wrote:
> Arjan van de Ven wrote:
> > Zhang, Yanmin wrote:
> > 
> >> If it's a single processor, the go backwards issue doesn't exist. 
> >> Below is
> >> my patch based on Arjan's. It's against 2.6.19-rc5-mm2.
> > 
> > Hi,
> > 
> > this patch is incorrect
> > 
> >> --- linux-2.6.19-rc5-mm2_arjan/arch/x86_64/kernel/setup.c    
> >> 2006-11-29 10:41:21.000000000 +0800
> >> +++ linux-2.6.19-rc5-mm2_arjan_fix/arch/x86_64/kernel/setup.c    
> >> 2006-11-29 10:42:28.000000000 +0800
> >> @@ -861,7 +861,7 @@ static void __cpuinit init_intel(struct          
> >> set_bit(X86_FEATURE_CONSTANT_TSC, &c->x86_capability);
> >>      if (c->x86 == 6)
> >>          set_bit(X86_FEATURE_REP_GOOD, &c->x86_capability);
> >> -    if (c->x86 == 15)
> >> +    if (c->x86 == 15 && num_possible_cpus() != 1)
> >>          set_bit(X86_FEATURE_SYNC_RDTSC, &c->x86_capability);
> > 
> > 
> > first of all, you probably meant "|| num_possible_cpus() == 1"
> > 
> > but second of all, the core2 cpus are dual core so.. .what does it bring 
> > you at all?
> 
> I guess you could boot with a UP kernel or maxcpus=1?
Yes, with the new patch. My reply email to Arjan was lost in LKML because
my email client was crazy to set the email as HTML format.

> 
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