linux-kernel - Re: [RFC patch] disable the assumption of apic_is_clustered

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Date:	Fri, 3 Jul 2009 10:36:10 +0800
From:	Luming Yu <luming.yu@...il.com>
To:	suresh.b.siddha@...el.com
Cc:	LKML <linux-kernel@...r.kernel.org>,
	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>
Subject: Re: [RFC patch] disable the assumption of apic_is_clustered_box for 
	cores >= 6

On Fri, Jul 3, 2009 at 3:04 AM, Suresh Siddha<suresh.b.siddha@...el.com> wrote:
> On Mon, 2009-06-29 at 19:53 -0700, Luming Yu wrote:
>> Hello,
>>
>> We have to disable the assumption of apic_is_clustered_box that assumes high
>> 4bits of 8 bit APIC ID was cluster id, which is just the function's guess.
>> On a normal 4-socket system with >6cores Processor and HT enabled, we hit the
>> limitation of the guess and failed. Have to disable the guess on any
>> cores > 6 system.
>>
>> Without this patch, we can't use good TSC on any SMP system with 48+ logical CPU
>
> This patch doesn't seem to be the right fix. BTW, it appears that
> Yinghai's patch in mainline appear to address this issue already. Did
> you check if the mainline still has the issue that you are trying to fix
> here?

Oh.. my testing kernel is still -rc6. The patch should fix the problem.
Thanks for the pointer. I believe I have heard of this patch, but don't know
why I didn't check that first before spending time on this fix,
although this patch didn't take
too much time, but does create some noise. I'm sorry about that.
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