[RFC v2] eal: provide option to use compiler memcpy instead of RTE

[Bruce Richardson]

On Tue, May 28, 2024 at 07:59:36AM -0700, Stephen Hemminger wrote:
> On Tue, 28 May 2024 10:19:15 +0200
> Mattias Rönnblom <hofors at lysator.liu.se> wrote:
> 
> > >   
> > 
> > I've tested this patch some with DSW micro benchmarks, and the result is 
> > a 2.5% reduction of the DSW+testapp overhead with cc/libc memcpy. GCC 11.4.
> > 
> > We've also run characteristic test suite of a large, real world app. 
> > Here, we saw no effect. GCC 10.5.
> > 
> > x86_64 in both cases (Skylake and Raptor Lake).
> > 
> > Last time we did the same, there were a noticeable performance 
> > degradation in both the above cases.
> > 
> > This is not a lot of data points, but I think it we should consider 
> > making the custom RTE memcpy() implementations optional in the next 
> > release, and if no-one complains, remove the implementations in the next 
> > release.
> 
> Lets go farther.
> 
> 1. Announce that rte_memcpy will be marked deprecated in 24.11 release
> 
> 2. In 24.11 do a global replace of rte_memcpy on the tree.
>    And mark rte_memcpy as deprecated.
> 
> 3. In 25.11 it can go away.

While I'd like us to be able to do so, I believe that to be premature. We
need to see where/if there are regressions first, and see about fixing
them.

/Bruce