linux-kernel - Re: [discuss] [PATCH 4/4 TRY#3] optimize and simplify get_cycles

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Message-ID: <20070312134500.GG8922@amd.com>
Date:	Mon, 12 Mar 2007 14:45:00 +0100
From:	"Joerg Roedel" <joerg.roedel@....com>
To:	"Michael Matz" <matz@...e.de>
cc:	"Avi Kivity" <avi@...o.co.il>, discuss@...-64.org,
	"Andi Kleen" <ak@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: [discuss] [PATCH 4/4 TRY#3] optimize and simplify
 get_cycles_sync()

On Mon, Mar 12, 2007 at 02:29:43PM +0100, Michael Matz wrote:
> Hi Joerg,
> 
> On Mon, 12 Mar 2007, Joerg Roedel wrote:
> 
> > > >+#define RDTSCP ".byte 0x0f, 0x01, 0xf9"
> > > >+	alternative_io_two("cpuid\nrdtsc",
> > > >+			   "rdtsc", X86_FEATURE_SYNC_RDTSC,
> > > >+			   ".byte 0x0f, 0x01, 0xf9", X86_FEATURE_RDTSCP,
> > > >  
> > > 
> > > why not use the RDTSCP macro here?
> > 
> > Does this macro exist?
> 
> Look carefully at your patch again, or at least the four quoted lines 
> above.  You've added it yourself, in exactly the form you'd need in the 
> alternative_io_two() call :-)

Hmmkay, thanks for opening my eyes :-)
I considered defining this macro while writing this patch, but decided
against this because the X86_FEATURE_RDTSCP on the same line should
documenting the opcode sufficiently. I just forgot to remove that
#define :)

Thanks again,
Joerg

-- 
Joerg Roedel
Operating System Research Center
AMD Saxony LLC & Co. KG


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