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.
