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lib/raid6/altivec: Add vpermxor implementation for raid6 Q syndrome

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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>
This commit is contained in:
Matt Brown
2017-08-04 13:42:32 +10:00
committed by Michael Ellerman
parent 7004263bd4
commit 751ba79cc5
7 changed files with 161 additions and 3 deletions
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6
arch/powerpc/include/asm/ppc-opcode.h
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@@ -271,6 +271,7 @@
#define PPC_INST_TLBSRX_DOT 0x7c0006a5
#define PPC_INST_VPMSUMW 0x10000488
#define PPC_INST_VPMSUMD 0x100004c8
#define PPC_INST_VPERMXOR 0x1000002d
#define PPC_INST_XXLOR 0xf0000490
#define PPC_INST_XXSWAPD 0xf0000250
#define PPC_INST_XVCPSGNDP 0xf0000780
@@ -517,6 +518,11 @@
#define XVCPSGNDP(t, a, b) stringify_in_c(.long (PPC_INST_XVCPSGNDP | \
VSX_XX3((t), (a), (b))))
#define VPERMXOR(vrt, vra, vrb, vrc) \
stringify_in_c(.long (PPC_INST_VPERMXOR | \
___PPC_RT(vrt) | ___PPC_RA(vra) | \
___PPC_RB(vrb) | (((vrc) & 0x1f) << 6)))
#define PPC_NAP stringify_in_c(.long PPC_INST_NAP)
#define PPC_SLEEP stringify_in_c(.long PPC_INST_SLEEP)
#define PPC_WINKLE stringify_in_c(.long PPC_INST_WINKLE)