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SubjectRe: [PATCH 3/5] perf core: Prepare writing into ring buffer from end
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On 2016/3/23 17:50, Peter Zijlstra wrote:
> On Mon, Mar 14, 2016 at 09:59:43AM +0000, Wang Nan wrote:
>> Convert perf_output_begin to __perf_output_begin and make the later
>> function able to write records from the end of the ring buffer.
>> Following commits will utilize the 'backward' flag.
>>
>> This patch doesn't introduce any extra performance overhead since we
>> use always_inline.
> So while I agree that with __always_inline and constant propagation we
> _should_ end up with the same code, we have:
>
> $ size defconfig-build/kernel/events/ring_buffer.o.{pre,post}
> text data bss dec hex filename
> 3785 2 0 3787 ecb defconfig-build/kernel/events/ring_buffer.o.pre
> 3673 2 0 3675 e5b defconfig-build/kernel/events/ring_buffer.o.post
>
> The patch actually makes the file shrink.
>
> So I think we still want to have some actual performance numbers.

There are some numbers. You can find them from:

http://lkml.iu.edu/hypermail/linux/kernel/1601.2/03966.html

Thank you.

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