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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@gmail.com>
Reviewed-by: Daniel Axtens <dja@axtens.net>
[mpe: Add VPERMXOR macro so we can build with old binutils]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
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Using vector registers is slightly faster:
raid6: vx128x8 gen() 19705 MB/s
raid6: vx128x8 xor() 11886 MB/s
raid6: using algorithm vx128x8 gen() 19705 MB/s
raid6: .... xor() 11886 MB/s, rmw enabled
vs the software algorithms:
raid6: int64x1 gen() 3018 MB/s
raid6: int64x1 xor() 1429 MB/s
raid6: int64x2 gen() 4661 MB/s
raid6: int64x2 xor() 3143 MB/s
raid6: int64x4 gen() 5392 MB/s
raid6: int64x4 xor() 3509 MB/s
raid6: int64x8 gen() 4441 MB/s
raid6: int64x8 xor() 3207 MB/s
raid6: using algorithm int64x4 gen() 5392 MB/s
raid6: .... xor() 3509 MB/s, rmw enabled
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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Rebased/reworked a patch contributed by Rob Herring that uses
NEON intrinsics to perform the RAID-6 syndrome calculations.
It uses the existing unroll.awk code to generate several
unrolled versions of which the best performing one is selected
at boot time.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Nicolas Pitre <nico@linaro.org>
Cc: hpa@linux.intel.com
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Another missing bit of the raid6 -> /lib move.
Reported-by: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: NeilBrown <neilb@suse.de>
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