[v6 1/2] raid6/altivec: Add vpermxor implementation for raid6 Q syndrome

[Michael Ellerman]

Matt Brown <matthew.brown.dev at gmail.com> writes:

> This patch uses the vpermxor instruction to optimise the raid6 Q syndrome.
> This instruction was made available with POWER8, ISA version 2.07.
> It allows for both vperm and vxor instructions to be done in a single
> instruction. This has been tested for correctness on a ppc64le vm with a
> basic RAID6 setup containing 5 drives.
>
> The performance benchmarks are from the raid6test in the /lib/raid6/test
> directory. These results are from an IBM Firestone machine with ppc64le
> architecture. The benchmark results show a 35% speed increase over the best
> existing algorithm for powerpc (altivec). The raid6test has also been run
> on a big-endian ppc64 vm to ensure it also works for big-endian
> architectures.
>
> Performance benchmarks:
> 		raid6: altivecx4 gen() 18773 MB/s
> 		raid6: altivecx8 gen() 19438 MB/s
>
> 		raid6: vpermxor4 gen() 25112 MB/s
> 		raid6: vpermxor8 gen() 26279 MB/s
>
> Signed-off-by: Matt Brown <matthew.brown.dev at gmail.com>
> Reviewed-by: Daniel Axtens <dja at axtens.net>
> ---
> v6:
> 	- added vpermxor files to .gitignore
> 	- fixup whitespace
> 	- added vpermxor objs to test/Makefile
> v5:
> 	- moved altivec.uc fix into other patch in series
> ---
>  include/linux/raid/pq.h |   4 ++
>  lib/raid6/.gitignore    |   1 +
>  lib/raid6/Makefile      |  27 ++++++++++++-
>  lib/raid6/algos.c       |   4 ++
>  lib/raid6/test/Makefile |  17 +++++++-
>  lib/raid6/vpermxor.uc   | 104 ++++++++++++++++++++++++++++++++++++++++++++++++
>  6 files changed, 154 insertions(+), 3 deletions(-)
>  create mode 100644 lib/raid6/vpermxor.uc

This version at least is not Cc'ed to any of the folks that
get_maintainers.pl identifies for these files:

$ ./scripts/get_maintainer.pl -f lib/raid6
shli at fb.com
gayatri.kammela at intel.com
fenghua.yu at intel.com
megha.dey at linux.intel.com
schwidefsky at de.ibm.com
anup.patel at broadcom.com
linux-kernel at vger.kernel.org


This seems like mostly a list of random folks who've touched this code,
but maybe some of them would have comments?

cheers