linux-kernel - Re: [RFT] Port 0x80 I/O speed

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Date:	Wed, 12 Dec 2007 00:23:04 -0500
From:	Kyle McMartin <kyle@...artin.ca>
To:	Rene Herman <rene.herman@...il.com>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>, dpreed@...d.com,
	Alan Cox <alan@...rguk.ukuu.org.uk>, pavel@....cz,
	andi@...stfloor.org, rol@...917.net,
	Krzysztof Halasa <khc@...waw.pl>, david@...idnewall.com,
	hpa@...or.com, john@...ffel.org, linux-os@...logic.com
Subject: Re: [RFT] Port 0x80 I/O speed

On Wed, Dec 12, 2007 at 12:31:18AM +0100, Rene Herman wrote:
> 	asm volatile ("rdtsc": "=A" (tsc));

rdtsc returns a 64-bit value in two 32-bit regs, you need to do

inline unsigned long long rdtsc(void)
{
	unsigned int lo, hi;
	asm volatile ("rdtsc": "=a" (lo), "=d" (hi));
	return (unsigned long long)hi << 32 | lo;
}

as in msr.h, otherwise you'll only be looking at the value in %rax.

cheers,
	Kyle
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