Re: [PATCH] powerpc: Align hot loops of memset() and backwards_memcpy()

On Sun, 25 Sep 2016 21:36:59 +1000
Anton Blanchard [off-list ref] wrote:

Hi Nick,

quoted

Hmm. If we execute this loop once, we'll only fetch additional nops.
Twice, and we make up for them by not fetching unused instructions.
More than twice and we may start winning.

For large sizes it probably helps, but I'd like to see what sizes
memset sees.  

I noticed this in an nginx web serving test. There are some 1 and 2
iteration calls, but quite a few larger ones - get_empty_filp() goes for
4 iterations and sk_prot_alloc() for 26 iterations.

Hi Anton,

I didn't have anything against the patch as such, I just wondered if
it's likely to be an overall win.

Thanks,
Nick