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

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Message-ID: <20081118080952.GE17838@elte.hu>
Date:	Tue, 18 Nov 2008 09:09:52 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Venki Pallipadi <venkatesh.pallipadi@...el.com>
Cc:	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


* 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?

	Ingo
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