Re: [PATCH 0/3] raid: remove obsolete MMX optimized code

[David Laight <david.laight.linux@gmail.com>]

On Sun, 25 Oct 2026 12:12:04 -0700
Eric Biggers <ebiggers@kernel.org> wrote:

> This series retires 32-bit MMX optimizations for RAID.
> 
> Affected CPUs, such as the Pentium MMX and Pentium II, will just fall
> back to the existing well-tested scalar code instead.

Seems like a good idea.
I wonder if all that loop unrolling was needed :-)

David

> 
> This was the only remaining MMX optimized code in the kernel.  MMX
> optimizations for the much more commonly called functions memcpy(),
> copy_page(), and clear_page() were already removed years ago by commit
> c6dbd3e5e69c ("x86/mmx_32: Remove X86_USE_3DNOW").  There are zero MMX
> optimizations for anything else, like crypto or CRC, which left the RAID
> code as an outlier.
> 
> Patch 3 also cleans up the CPU feature checks in the RAID6 code.
> 
> Eric Biggers (3):
>   xor: remove MMX optimized code
>   raid6: remove MMX optimized code
>   raid6: simplify CPU feature checks
> 
>  lib/raid/raid6/Makefile      |   4 -
>  lib/raid/raid6/x86/mmx.c     | 118 --------
>  lib/raid/raid6/x86/pq_arch.h |  69 +----
>  lib/raid/raid6/x86/sse1.c    | 136 ---------
>  lib/raid/xor/Makefile        |   2 +-
>  lib/raid/xor/x86/xor-mmx.c   | 515 -----------------------------------
>  lib/raid/xor/x86/xor_arch.h  |   5 -
>  7 files changed, 12 insertions(+), 837 deletions(-)
>  delete mode 100644 lib/raid/raid6/x86/mmx.c
>  delete mode 100644 lib/raid/raid6/x86/sse1.c
>  delete mode 100644 lib/raid/xor/x86/xor-mmx.c
> 
> 
> base-commit: 21a7f44fd0765fcc5194130b28767786eba1d1e7