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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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

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)

4
include/linux/raid/pq.h
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@ -107,6 +107,10 @@ extern const struct raid6_calls raid6_avx512x2;
extern const struct raid6_calls raid6_avx512x4;
extern const struct raid6_calls raid6_tilegx8;
extern const struct raid6_calls raid6_s390vx8;
extern const struct raid6_calls raid6_vpermxor1;
extern const struct raid6_calls raid6_vpermxor2;
extern const struct raid6_calls raid6_vpermxor4;
extern const struct raid6_calls raid6_vpermxor8;
struct raid6_recov_calls {
void (*data2)(int, size_t, int, int, void **);

1
lib/raid6/.gitignore vendored
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@ -4,3 +4,4 @@ int*.c
tables.c
neon?.c
s390vx?.c
vpermxor*.c

27
lib/raid6/Makefile
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@ -5,7 +5,8 @@ raid6_pq-y += algos.o recov.o tables.o int1.o int2.o int4.o \
int8.o int16.o int32.o
raid6_pq-$(CONFIG_X86) += recov_ssse3.o recov_avx2.o mmx.o sse1.o sse2.o avx2.o avx512.o recov_avx512.o
raid6_pq-$(CONFIG_ALTIVEC) += altivec1.o altivec2.o altivec4.o altivec8.o
raid6_pq-$(CONFIG_ALTIVEC) += altivec1.o altivec2.o altivec4.o altivec8.o \
vpermxor1.o vpermxor2.o vpermxor4.o vpermxor8.o
raid6_pq-$(CONFIG_KERNEL_MODE_NEON) += neon.o neon1.o neon2.o neon4.o neon8.o recov_neon.o recov_neon_inner.o
raid6_pq-$(CONFIG_TILEGX) += tilegx8.o
raid6_pq-$(CONFIG_S390) += s390vx8.o recov_s390xc.o
@ -91,6 +92,30 @@ $(obj)/altivec8.c: UNROLL := 8
$(obj)/altivec8.c: $(src)/altivec.uc $(src)/unroll.awk FORCE
$(call if_changed,unroll)
CFLAGS_vpermxor1.o += $(altivec_flags)
targets += vpermxor1.c
$(obj)/vpermxor1.c: UNROLL := 1
$(obj)/vpermxor1.c: $(src)/vpermxor.uc $(src)/unroll.awk FORCE
$(call if_changed,unroll)
CFLAGS_vpermxor2.o += $(altivec_flags)
targets += vpermxor2.c
$(obj)/vpermxor2.c: UNROLL := 2
$(obj)/vpermxor2.c: $(src)/vpermxor.uc $(src)/unroll.awk FORCE
$(call if_changed,unroll)
CFLAGS_vpermxor4.o += $(altivec_flags)
targets += vpermxor4.c
$(obj)/vpermxor4.c: UNROLL := 4
$(obj)/vpermxor4.c: $(src)/vpermxor.uc $(src)/unroll.awk FORCE
$(call if_changed,unroll)
CFLAGS_vpermxor8.o += $(altivec_flags)
targets += vpermxor8.c
$(obj)/vpermxor8.c: UNROLL := 8
$(obj)/vpermxor8.c: $(src)/vpermxor.uc $(src)/unroll.awk FORCE
$(call if_changed,unroll)
CFLAGS_neon1.o += $(NEON_FLAGS)
targets += neon1.c
$(obj)/neon1.c: UNROLL := 1

4
lib/raid6/algos.c
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@ -74,6 +74,10 @@ const struct raid6_calls * const raid6_algos[] = {
&raid6_altivec2,
&raid6_altivec4,
&raid6_altivec8,
&raid6_vpermxor1,
&raid6_vpermxor2,
&raid6_vpermxor4,
&raid6_vpermxor8,
#endif
#if defined(CONFIG_TILEGX)
&raid6_tilegx8,

17
lib/raid6/test/Makefile
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@ -48,7 +48,8 @@ else
gcc -c -x c - >&/dev/null && \
rm ./-.o && echo yes)
ifeq ($(HAS_ALTIVEC),yes)
OBJS += altivec1.o altivec2.o altivec4.o altivec8.o
OBJS += altivec1.o altivec2.o altivec4.o altivec8.o \
vpermxor1.o vpermxor2.o vpermxor4.o vpermxor8.o
endif
endif
ifeq ($(ARCH),tilegx)
@ -98,6 +99,18 @@ altivec4.c: altivec.uc ../unroll.awk
altivec8.c: altivec.uc ../unroll.awk
$(AWK) ../unroll.awk -vN=8 < altivec.uc > $@
vpermxor1.c: vpermxor.uc ../unroll.awk
$(AWK) ../unroll.awk -vN=1 < vpermxor.uc > $@
vpermxor2.c: vpermxor.uc ../unroll.awk
$(AWK) ../unroll.awk -vN=2 < vpermxor.uc > $@
vpermxor4.c: vpermxor.uc ../unroll.awk
$(AWK) ../unroll.awk -vN=4 < vpermxor.uc > $@
vpermxor8.c: vpermxor.uc ../unroll.awk
$(AWK) ../unroll.awk -vN=8 < vpermxor.uc > $@
int1.c: int.uc ../unroll.awk
$(AWK) ../unroll.awk -vN=1 < int.uc > $@
@ -123,7 +136,7 @@ tables.c: mktables
./mktables > tables.c
clean:
rm -f *.o *.a mktables mktables.c *.uc int*.c altivec*.c neon*.c tables.c raid6test
rm -f *.o *.a mktables mktables.c *.uc int*.c altivec*.c vpermxor*.c neon*.c tables.c raid6test
rm -f tilegx*.c
spotless: clean

105
lib/raid6/vpermxor.uc Normal file
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@ -0,0 +1,105 @@
/*
* Copyright 2017, Matt Brown, IBM Corp.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
* vpermxor$#.c
*
* Based on H. Peter Anvin's paper - The mathematics of RAID-6
*
* $#-way unrolled portable integer math RAID-6 instruction set
* This file is postprocessed using unroll.awk
*
* vpermxor$#.c makes use of the vpermxor instruction to optimise the RAID6 Q
* syndrome calculations.
* This can be run on systems which have both Altivec and vpermxor instruction.
*
* This instruction was introduced in POWER8 - ISA v2.07.
*/
#include <linux/raid/pq.h>
#ifdef CONFIG_ALTIVEC
#include <altivec.h>
#ifdef __KERNEL__
#include <asm/cputable.h>
#include <asm/ppc-opcode.h>
#include <asm/switch_to.h>
#endif
typedef vector unsigned char unative_t;
#define NSIZE sizeof(unative_t)
static const vector unsigned char gf_low = {0x1e, 0x1c, 0x1a, 0x18, 0x16, 0x14,
0x12, 0x10, 0x0e, 0x0c, 0x0a, 0x08,
0x06, 0x04, 0x02,0x00};
static const vector unsigned char gf_high = {0xfd, 0xdd, 0xbd, 0x9d, 0x7d, 0x5d,
0x3d, 0x1d, 0xe0, 0xc0, 0xa0, 0x80,
0x60, 0x40, 0x20, 0x00};
static void noinline raid6_vpermxor$#_gen_syndrome_real(int disks, size_t bytes,
void **ptrs)
{
u8 **dptr = (u8 **)ptrs;
u8 *p, *q;
int d, z, z0;
unative_t wp$$, wq$$, wd$$;
z0 = disks - 3; /* Highest data disk */
p = dptr[z0+1]; /* XOR parity */
q = dptr[z0+2]; /* RS syndrome */
for (d = 0; d < bytes; d += NSIZE*$#) {
wp$$ = wq$$ = *(unative_t *)&dptr[z0][d+$$*NSIZE];
for (z = z0-1; z>=0; z--) {
wd$$ = *(unative_t *)&dptr[z][d+$$*NSIZE];
/* P syndrome */
wp$$ = vec_xor(wp$$, wd$$);
/* Q syndrome */
asm(VPERMXOR(%0,%1,%2,%3):"=v"(wq$$):"v"(gf_high), "v"(gf_low), "v"(wq$$));
wq$$ = vec_xor(wq$$, wd$$);
}
*(unative_t *)&p[d+NSIZE*$$] = wp$$;
*(unative_t *)&q[d+NSIZE*$$] = wq$$;
}
}
static void raid6_vpermxor$#_gen_syndrome(int disks, size_t bytes, void **ptrs)
{
preempt_disable();
enable_kernel_altivec();
raid6_vpermxor$#_gen_syndrome_real(disks, bytes, ptrs);
disable_kernel_altivec();
preempt_enable();
}
int raid6_have_altivec_vpermxor(void);
#if $# == 1
int raid6_have_altivec_vpermxor(void)
{
/* Check if arch has both altivec and the vpermxor instructions */
# ifdef __KERNEL__
return (cpu_has_feature(CPU_FTR_ALTIVEC_COMP) &&
cpu_has_feature(CPU_FTR_ARCH_207S));
# else
return 1;
#endif
}
#endif
const struct raid6_calls raid6_vpermxor$# = {
raid6_vpermxor$#_gen_syndrome,
NULL,
raid6_have_altivec_vpermxor,
"vpermxor$#",
0
};
#endif