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

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Date:	Thu, 20 Aug 2009 17:19:23 -0400
From:	William Cohen <wcohen@...hat.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC:	Paul Mackerras <paulus@...ba.org>, Ingo Molnar <mingo@...e.hu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Add minimal support for software performance counters
 for ia64

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.

-Will
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