linux-kernel - Re: [PATCH] x86: Support always running TSC on Intel CPUs

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Message-ID: <20081118145540.GA32082@tsunami.ccur.com>
Date:	Tue, 18 Nov 2008 09:55:40 -0500
From:	Joe Korty <joe.korty@...r.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Venki Pallipadi <venkatesh.pallipadi@...el.com>,
	H Peter Anvin <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: Support always running TSC on Intel CPUs

On Tue, Nov 18, 2008 at 09:09:52AM +0100, Ingo Molnar wrote:
> 
> * Venki Pallipadi <venkatesh.pallipadi@...el.com> wrote:
> 
> > +	if (c->x86_power & (1 << 8)) {
> >  		set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
> > +		set_cpu_cap(c, X86_FEATURE_NOSTOP_TSC);
> > +	}
> 
> hm, the naming is a bit confusing. We now have 3 variants:
> 
>   X86_FEATURE_TSC
>   X86_FEATURE_CONSTANT_TSC
>   X86_FEATURE_NOSTOP_TSC
> 
> NOSTOP_TSC is basically what CONSTANT_TSC should have been to begin 
> with ;-)
> 
> i'd suggest to rename it to this:
> 
>   X86_FEATURE_TSC
>   X86_FEATURE_CONSTANT_FREQ_TSC
>   X86_FEATURE_STABLE_TSC
> 
> ... with CONSTANT_FREQ_TSC not having any real role in the long run. 
> (it's similarly problematic to a completely unstable TSC)
> 
> does this sound ok?


To me, the new naming has the same head-scratching potential
as the old....

How about:

	X86_FEATURE_TSC
	X86_FEATURE_STABLE_TSC_OBSOLETE
	X86_FEATURE_STABLE_TSC

Joe
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