On Mon, Dec 14, 2020 at 08:50:00AM +0100, Julian Andres Klode wrote:
> Package: src:xxhash
> Version: 0.8.0-1
> Severity: normal
>
> XXH3 supports various hardware-accelerated variants in
> xxh_x86dispatch.{c,h}, which are currently not built into the library.
>
> This means that it only operates at roughly half the speed on my Core
> i5-8250U compared to the AVX2-accelerated variant.
>
> The implementation is odd: Client code explcitly has to use the
> xxh_x86dispatch.h header instead of the xxhash.h one. It would be more
> convenient if any code that includes xxhash.h on x86 automatically
> benefits from dispatched optimized code.
>
> At the bare minimum, on x86, export DIGEST=1 when building and install
> xxh_x86dispatch.h header. I'd love to see the xxh_x86dispatch.h also
> replace the xxhash.h header on x86 (still keeping xxh_x86dispatch.h in
> case people look for it) such that clients can directly benefit from it
> even if they do not handle looking up that header and using it.
I think I want to retract the "automatic" wish, because let's face it,
clients may have valid reasons to pick one or the other. But clearly
the situation is a bit suboptimal with the header being x86 only - their
really ought to be a discussion with upstream about how to generalize
this such that there is one scenario for any hw-acceleration enablement
across architectures.
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