• Matt Brown's avatar
    lib/raid6/altivec: Add vpermxor implementation for raid6 Q syndrome · 751ba79c
    Matt Brown authored
    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: default avatarMatt Brown <matthew.brown.dev@gmail.com>
    Reviewed-by: default avatarDaniel Axtens <dja@axtens.net>
    [mpe: Add VPERMXOR macro so we can build with old binutils]
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    751ba79c
vpermxor.uc 2.68 KB