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raid6: Add LoongArch SIMD recovery implementation

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Similar to the syndrome calculation, the recovery algorithms also work
on 64 bytes at a time to align with the L1 cache line size of current
and future LoongArch cores (that we care about). Which means
unrolled-by-4 LSX and unrolled-by-2 LASX code.

The assembly is originally based on the x86 SSSE3/AVX2 ports, but
register allocation has been redone to take advantage of LSX/LASX's 32
vector registers, and instruction sequence has been optimized to suit
(e.g. LoongArch can perform per-byte srl and andi on vectors, but x86
cannot).

Performance numbers measured by instrumenting the raid6test code, on a
3A5000 system clocked at 2.5GHz:

> lasx  2data: 354.987 MiB/s
> lasx  datap: 350.430 MiB/s
> lsx   2data: 340.026 MiB/s
> lsx   datap: 337.318 MiB/s
> intx1 2data: 164.280 MiB/s
> intx1 datap: 187.966 MiB/s

Because recovery algorithms are chosen solely based on priority and
availability, lasx is marked as priority 2 and lsx priority 1. At least
for the current generation of LoongArch micro-architectures, LASX should
always be faster than LSX whenever supported, and have similar power
consumption characteristics (because the only known LASX-capable uarch,
the LA464, always compute the full 256-bit result for vector ops).

Acked-by: Song Liu <song@kernel.org>
Signed-off-by: WANG Xuerui <git@xen0n.name>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
This commit is contained in:
WANG Xuerui 2023-09-06 22:53:55 +08:00 • committed by Huacai Chen
parent 8f3f06dfd6
commit f209132104
5 changed files with 525 additions and 2 deletions
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8
lib/raid6/algos.c
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@ -111,6 +111,14 @@ const struct raid6_recov_calls *const raid6_recov_algos[] = {
#endif
#if defined(CONFIG_KERNEL_MODE_NEON)
&raid6_recov_neon,
#endif
#ifdef CONFIG_LOONGARCH
#ifdef CONFIG_CPU_HAS_LASX
&raid6_recov_lasx,
#endif
#ifdef CONFIG_CPU_HAS_LSX
&raid6_recov_lsx,
#endif
#endif
&raid6_recov_intx1,
NULL