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3 Commits

Author SHA1 Message Date
Ard Biesheuvel
35129dde88 md/raid6: use faster multiplication for ARM NEON delta syndrome 
The P/Q left side optimization in the delta syndrome simply involves
repeatedly multiplying a value by polynomial 'x' in GF(2^8). Given
that 'x * x * x * x' equals 'x^4' even in the polynomial world, we
can accelerate this substantially by performing up to 4 such operations
at once, using the NEON instructions for polynomial multiplication.

Results on a Cortex-A57 running in 64-bit mode:

  Before:
  -------
  raid6: neonx1   xor()  1680 MB/s
  raid6: neonx2   xor()  2286 MB/s
  raid6: neonx4   xor()  3162 MB/s
  raid6: neonx8   xor()  3389 MB/s

  After:
  ------
  raid6: neonx1   xor()  2281 MB/s
  raid6: neonx2   xor()  3362 MB/s
  raid6: neonx4   xor()  3787 MB/s
  raid6: neonx8   xor()  4239 MB/s

While we're at it, simplify MASK() by using a signed shift rather than
a vector compare involving a temp register.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
 2017-08-09 18:51:57 +01:00
Ard Biesheuvel
0e833e697b md/raid6: delta syndrome for ARM NEON 
This implements XOR syndrome calculation using NEON intrinsics.
As before, the module can be built for ARM and arm64 from the
same source.

Relative performance on a Cortex-A57 based system:

  raid6: int64x1  gen()   905 MB/s
  raid6: int64x1  xor()   881 MB/s
  raid6: int64x2  gen()  1343 MB/s
  raid6: int64x2  xor()  1286 MB/s
  raid6: int64x4  gen()  1896 MB/s
  raid6: int64x4  xor()  1321 MB/s
  raid6: int64x8  gen()  1773 MB/s
  raid6: int64x8  xor()  1165 MB/s
  raid6: neonx1   gen()  1834 MB/s
  raid6: neonx1   xor()  1278 MB/s
  raid6: neonx2   gen()  2528 MB/s
  raid6: neonx2   xor()  1942 MB/s
  raid6: neonx4   gen()  2888 MB/s
  raid6: neonx4   xor()  2334 MB/s
  raid6: neonx8   gen()  2957 MB/s
  raid6: neonx8   xor()  2232 MB/s
  raid6: using algorithm neonx8 gen() 2957 MB/s
  raid6: .... xor() 2232 MB/s, rmw enabled

Cc: Markus Stockhausen <stockhausen@collogia.de>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NeilBrown <neilb@suse.com>
 2015-08-31 19:29:05 +02:00
Ard Biesheuvel
7d11965ddb lib/raid6: add ARM-NEON accelerated syndrome calculation 
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
 2013-07-08 22:09:18 +01:00