Re: [PATCH v2] raid6: arm64: add SVE optimized implementation for syndrome generation

[Robin Murphy]

On 16/04/2026 5:47 pm, Mark Brown wrote:
> On Thu, Apr 16, 2026 at 05:26:08PM +0100, Robin Murphy wrote:
>
> > Unless you've got a CPU with truly big wide vector units that _can't_ be
> > fully utilised by ASMID ops, then SVE is only really offering whatever
> > incidental benefits fall out of smaller code size. However, if you do have
> > those wider vectors, then the cost of correctly saving/restoring the SVE
> > state - of which a userspace benchmark isn't likely to be very
> > representative - is also going to scale up significantly.
>
> The other case will be when there's some SVE only extension that
> accelerates something that's relevant for the algorithm.  That's not
> really a thing at present but I imagine that we'll run into that at some
> point.

Indeed - I was implicitly thinking in terms of things that _are_ just 
transliterated from NEON to SVE, where the primary gain is stuff like 
predicate loops, but even that _could_ potentially be enough to justify 
an argument in-kernel SVE (using a 128-bit VL to keep the additional 
state/cost to a minimum).

Cheers,
Robin.