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

Anton Blanchard anton at samba.org
Sun Sep 25 21:36:59 AEST 2016


Hi Nick,

> 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.

Anton


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