linux-kernel - Re: [PATCH] Add minimal support for software performance counters for ia64

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Message-ID: <4A8EB8A9.9000900@redhat.com>
Date:	Fri, 21 Aug 2009 11:09:29 -0400
From:	William Cohen <wcohen@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Add minimal support for software performance counters
 for ia64

Ingo Molnar wrote:
> * William Cohen <wcohen@...hat.com> wrote:
> 
>> Peter Zijlstra wrote:
>>> On Wed, 2009-08-19 at 15:04 -0400, William Cohen wrote:
>>>> Peter Zijlstra wrote:
>>>>> On Wed, 2009-08-19 at 12:04 -0400, William Cohen wrote:
>>>>>> +#ifdef __ia64__
>>>>>> +#include "../../arch/ia64/include/asm/unistd.h"
>>>>>> +#define rmb()          asm volatile("" ::: "memory")
>>>>>> +#define cpu_relax()    asm volatile("" ::: "memory");
>>>>>> +#endif
>>>>> Surely the itanic has a real memory barrier? The kernel seems to use
>>>>> something along the lines of mf.
>>>>>
>>>>> Also, cpu_relax() seems to end up being asm volatile("hint @pause" :::
>>>>> "memory"), although we don't seem to have an actual user of cpu_relax()
>>>>> in perf atm.
>>>>>
>>>>>
>>>>>
>>>> Peter, thanks for the comment. I took a look at the rmb() and cpu_relax() code
>>>> in the kernel and revised the patch with the appropriate defines
>>> Looks good now, thanks!
>>>
>> When looking through the patch today I realized the new 
>> perf_counter.h was placed in include/asm-ia64. It should be placed 
>> in arch/ia64/include/asm/perf_counter.h.
> 
> mind sending out a v2 patch with all review feedback folded in, for 
> IA64 maintainers to ack if they like it?
> 
> Thanks,
> 
> 	Ingo

Hi Ingo,

The following is the revised patch with the corrected macros and the include
file in the correct place.

Signed-off-by: William Cohen <wcohen@...hat.com>

-Will

View attachment "perf_ia64c.patch" of type "text/plain" (4026 bytes)