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

Matt Brown [off-list ref] 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 <redacted>
Reviewed-by: Daniel Axtens <redacted>
---
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@fb.com
gayatri.kammela@intel.com
fenghua.yu@intel.com
megha.dey@linux.intel.com
schwidefsky@de.ibm.com
anup.patel@broadcom.com
linux-kernel@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