Re: [PATCH 3/4] sparc: Use default memcpy for rtld objects

[David Miller <davem at davemloft dot net>]

From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Thu, 5 Oct 2017 15:02:02 -0300

> Thanks for the explanation, although it does not explain why the ultra1
> is currently the default for sparc64 (sysdeps/sparc/sparc64/memcpy.S)
> and also the default selection for multiarch.  The C version is used
> solely for loader currently.

I never got around to fixing up this situation on the glibc side,
that's why.

> I tried to check which are the performance of C implementation against
> ultra1 one on a niagara5 and results are:
> 
>   - on bench-memcpy the C version is slight slower for sizes up to
>     32 (about 4% faster for sizes up to 16, 40% from 16 to 32 and
>     50% up to 32).  It is definitely faster for sizes higher than
>     64 (62% faster for sizes from 64 to 128 and 85% for sizes
>     higher than 128).
> 
>   - on bench-memcpy-random shows no performance difference, however
>     bench-memcpy-large shows the C implementation is indeed faster
>     for all inputs.
> 
> So I think that instead of using default memcpy for rtld, the best
> strategy would to use the C implementation instead as default and
> add ultra1 as another option for ifunc resolution.

Yes, that's a good way to go.