linux-kernel - Re: [PATCH] x86: X86_HT always enable on X86

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Message-ID: <47C5E158.5080900@ct.jp.nec.com>
Date:	Wed, 27 Feb 2008 14:16:56 -0800
From:	Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
To:	Adrian Bunk <bunk@...nel.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Sam Ravnborg <sam@...nborg.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: X86_HT always enable on X86_64 SMP

Adrian Bunk wrote:
> On Wed, Feb 27, 2008 at 01:30:59PM -0800, H. Peter Anvin wrote:
>> Adrian Bunk wrote:
>>> On Wed, Feb 27, 2008 at 01:16:30PM -0800, Hiroshi Shimamoto wrote:
>>>> From: Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
>>>>
>>>> X86_HT is used for hyperthreading or multicore on 32-bit.
>>>> The X86_HT on 64-bit is different from 32-bit, it means hyperthreading only.
>>>> And X86_HT is not used on 64-bit except from cpu/initel_cacheinfo.c.
>>>>
>>>> Unify X86_HT for hyperthreading or multicore.
>>>> Turn X86_HT on when X86_64 and SMP are enabled.
>>> Please fix it properly instead - fiddling around with it the way you do
>>> only asks for trouble in the future.
>>>
>>> What we need are two different variables for:
>>> - hyperthreading and
>>> - multicore
>> He does, and calls them SCHED_SMT and SCHED_MC respectively.
> 
> These are the already existing scheduler related variables that are 
> only a part of the X86_HT usages.
> 
>> It's not particularly clear to me what X86_HT is meant to be used for  
>> anymore at all.
> 
> grep through the source code and you find it is sometimes used for 
> hyperthreading and sometimes for multicore.
> 
> I don't care whether X86_HT gets splitted or perhaps even removed, but 
> any change to it should remove the status quo of it having two different 
> semantics.

OK, you say "Don't mix two different semantics into one variable X86_HT", right?

Thanks,
Hiroshi Shimamoto
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