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....@gmail.com>
Reviewed-by: Daniel Axtens <d...@axtens.net>
---
v6:
- added vpermxor files to .gitignore
- fixup whitespace
- added vpermxor objs to test/Makefile
v5:
- moved altivec.uc fix into other patch in series
---
include/linux/raid/pq.h | 4 ++
lib/raid6/.gitignore | 1 +
lib/raid6/Makefile | 27 ++++++++++++-
lib/raid6/algos.c | 4 ++
lib/raid6/test/Makefile | 17 +++++++-
lib/raid6/vpermxor.uc | 104 ++++++++++++++++++++++++++++++++++++++++++++++++
6 files changed, 154 insertions(+), 3 deletions(-)
create mode 100644 lib/raid6/vpermxor.uc
diff --git a/include/linux/raid/pq.h b/include/linux/raid/pq.h
index 4d57bba..3df9aa6 100644
--- a/include/linux/raid/pq.h
+++ b/include/linux/raid/pq.h
@@ -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 **);
diff --git a/lib/raid6/.gitignore b/lib/raid6/.gitignore
index f01b1cb..3de0d89 100644
--- a/lib/raid6/.gitignore
+++ b/lib/raid6/.gitignore
@@ -4,3 +4,4 @@ int*.c
tables.c
neon?.c
s390vx?.c
+vpermxor*.c
diff --git a/lib/raid6/Makefile b/lib/raid6/Makefile
index 3057011..db095a7 100644
--- a/lib/raid6/Makefile
+++ b/lib/raid6/Makefile
@@ -4,7 +4,8 @@ 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
raid6_pq-$(CONFIG_TILEGX) += tilegx8.o
raid6_pq-$(CONFIG_S390) += s390vx8.o recov_s390xc.o
@@ -88,6 +89,30 @@ $(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
$(obj)/neon1.c: UNROLL := 1
diff --git a/lib/raid6/algos.c b/lib/raid6/algos.c
index 7857049..edd4f69 100644
--- a/lib/raid6/algos.c
+++ b/lib/raid6/algos.c
@@ -74,6 +74,10 @@ const struct raid6_calls * const raid6_algos[] = {
&raid6_altivec2,
&raid6_altivec4,
&raid6_altivec8,
+ &raid6_vpermxor1,
+ &raid6_vpermxor2,
+ &raid6_vpermxor4,
+ &raid6_vpermxor8,
#endif
#if defined(CONFIG_TILEGX)
&raid6_tilegx8,
diff --git a/lib/raid6/test/Makefile b/lib/raid6/test/Makefile
index 2c7b60e..a14be53 100644
--- a/lib/raid6/test/Makefile
+++ b/lib/raid6/test/Makefile
@@ -47,7 +47,8 @@ else
gcc -c -x c - >&/dev/null && \
rm ./-.o && echo yes)
ifeq ($(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)
@@ -97,6 +98,18 @@ 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 > $@
@@ -122,7 +135,7 @@ tables.c: mktables
./mktables > tables.c
clean:
- rm -f *.o *.a mktables mktables.c *.uc int*.c altivec*.c neon*.c
tables.c raid6test
+ rm -f *.o *.a mktables mktables.c *.uc int*.c altivec*.c vpermxor*.c
neon*.c tables.c raid6test
rm -f tilegx*.c
spotless: clean
diff --git a/lib/raid6/vpermxor.uc b/lib/raid6/vpermxor.uc
new file mode 100644
index 0000000..22d743a
--- /dev/null
+++ b/lib/raid6/vpermxor.uc
@@ -0,0 +1,104 @@
+/*
+ * Copyright 2017, Matt Brown, IBM Corp.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ *
+ * vpermxor$#.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/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
--
2.9.3
