Re: [PATCH v2 1/3] perf util: Add BLAKE2s support

[Eric Biggers <ebiggers@kernel.org>]

On Tue, Jan 13, 2026 at 05:00:37PM -0300, Arnaldo Carvalho de Melo wrote:
> On Mon, Dec 08, 2025 at 05:57:27PM -0800, Eric Biggers wrote:
> > Add BLAKE2s support to the perf utility library.  The code is borrowed
> > from the kernel.
> 
> We have tools/perf/check-headers.sh to check for drifts between things
> we borrow from the kernel, so that when the kernel fixes or improves
> things we borrowed, we notice and check if it makes sense for us to
> update the copy, see tools/include/uapi/README.
> 
> In this case the copy isn't verbatim, as not all is needed, perhaps it
> could be just to facilitate? I haven't checked, just mentioning it while
> processing this series, I'll check that later, maybe.
> 
> - Arnaldo

I think that would be more trouble than it's worth in this case.  Every
time I make a change to a UAPI header, even something trivial like
updating a comment, I start getting emails about how a header changed
and perf's copy of it is being updated too.  It's actually kind of
annoying.  I don't think we need to add that for the BLAKE2s code too.

We can always resynchronize manually later if there's an important
change.

But ultimately this code just implements BLAKE2s, which is a fixed
algorithm.  If it does so correctly, which I'm quite confident it does,
future changes will just be refactoring, optimization, etc.

Of course, the use of BLAKE2s in 'perf' doesn't seem to be
performance-critical, so any optimizations won't be that important for
it.  It will include just the generic C code anyway -- no assembly code.

- Eric