Re: [PATCH v4 6/8] x86/ftrace: Use __pa_symbol instead of __pa onC visible symbols

[Alexander Duyck]

On 11/16/2012 03:06 PM, H. Peter Anvin wrote:
> On 11/16/2012 02:45 PM, Steven Rostedt wrote:
>>
>> #define __pa(x)        __phys_addr((unsigned long)(x))
>> #define __pa_symbol(x)    __pa(__phys_reloc_hide((unsigned long)(x)))
>>
>> I'm confused. __pa_symbol() just calls __pa() with some macro magic to
>> its parameter. How is this a performance improvement?
>>
>
> One of the earlier patches in this series changes __pa_symbol() to
> avoid the conditional hidden inside __phys_addr(), since by definition
> a symbol can only be on one side of that branch.
>
>     -hpa
>

In addition to being a bit faster the code is also a bit smaller since
it can combine the the constants from __va() and __pa_symbol() as the
new __pa_symbol is an inline in the non-debug case.

Thanks,

Alex
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