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

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Message-ID: <45F57AEB.5030405@argo.co.il>
Date:	Mon, 12 Mar 2007 18:08:11 +0200
From:	Avi Kivity <avi@...o.co.il>
To:	Joerg Roedel <joerg.roedel@....com>
CC:	discuss@...-64.org, Andi Kleen <ak@...e.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4 TRY#3] optimize and simplify get_cycles_sync()

Joerg Roedel wrote:
> On Fri, Mar 09, 2007 at 08:10:03PM +0200, Avi Kivity wrote:
>   
>> Joerg Roedel wrote:
>>     
>>> From: Joerg Roedel <joerg.roedel@....com>
>>>
>>> This patch simplifies the get_cycles_sync() function by removing
>>> the #ifdefs from it. Further it introduces an optimization for AMD
>>> processors. There the RDTSCP instruction is used instead of CPUID;RDTSC
>>> which is helpfull if the kernel runs as a KVM guest. Running as a guest
>>> makes CPUID very expensive because it causes an intercept of the guest.
>>>
>>>  +#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? I couldn't found it in the current git tree. And
> the rdtscp macros in msr.h use the plain opcode too.
>   

-ENOCOFFEE?  You defined the macro 3 lines above the .byte directive...


-- 
error compiling committee.c: too many arguments to function

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