Re: [v2] raid6/altivec: Add vpermxor implementation for raid6 Q syndrome

[Michael Ellerman]

Daniel Axtens  writes:

> Hi Matt,
>
> Thanks for answering my questions and doing those fixes.
>
>
>> Bugs fixed:
>>  - A small bug in pq.h regarding a missing and mismatched
>>ifdef statement
>>  - Fixed test/Makefile to correctly build test on ppc
>>
>
> I think this commit should be labelled:
> Fixes: 4f8c55c5ad49 ("lib/raid6: build proper files on corresponding arch")
>
> mpe can probably add that when he merges - no need to do a new version :)

Please send a separate patch which does that fix.

>>  else
>> -HAS_ALTIVEC := $(shell printf '\#include \nvector int 
>> a;\n' |\
>> - gcc -c -x c - >&/dev/null && \
>> - rm ./-.o && echo yes)
>> -ifeq ($(HAS_ALTIVEC),yes)
>> -OBJS += altivec1.o altivec2.o altivec4.o altivec8.o
>> + HAS_ALTIVEC := $(shell printf '\#include \nvector int a;\n' 
>> |\
>> + gcc -c -x c - >/dev/null && rm ./-.o && echo yes)
>> + ifeq ($(HAS_ALTIVEC),yes)
>> +CFLAGS += -I../../../arch/powerpc/include
>> +CFLAGS += -DCONFIG_ALTIVEC
>> +OBJS += altivec1.o altivec2.o altivec4.o altivec8.o \
>> +vpermxor1.o vpermxor2.o vpermxor4.o vpermxor8.o
>>  endif
>>  endif
> Looks like vim has replaced spaces with tabs here. Not sure how much we
> care...

We care at least because it makes the diff look bigger than it really
is, if I'm reading it right the first three lines haven't actually
changed.

>> @@ -97,6 +99,18 @@ altivec4.c: altivec.uc ../unroll.awk
>>  altivec8.c: altivec.uc ../unroll.awk
>>  $(AWK) ../unroll.awk -vN=8 < altivec.uc > $@
>>
> ... especially seeing as tabs are already used in the file here!

It's a Makefile! Tabs have meaning :)

>> +# ifdef __KERNEL__
>> +return (cpu_has_feature(CONFIG_ALTIVEC) &&
>> +cpu_has_feature(CPU_FTR_ARCH_207S));
> I think CPU_FTR_ARCH_207S implies Altivec? Again, not a real problem,

It doesn't.

And also CONFIG_ALTIVEC is not a cpu feature!

You should be using CPU_FTR_ALTIVEC_COMP. That copes with the case where
the kernel is compiled without ALTIVEC support.

cheers

Re: [v2] raid6/altivec: Add vpermxor implementation for raid6 Q syndrome

[Daniel Axtens]

Hi Matt,

Thanks for answering my questions and doing those fixes.


> Bugs fixed:
>   - A small bug in pq.h regarding a missing and mismatched
> ifdef statement
>   - Fixed test/Makefile to correctly build test on ppc
>

I think this commit should be labelled:
Fixes: 4f8c55c5ad49 ("lib/raid6: build proper files on corresponding arch")

mpe can probably add that when he merges - no need to do a new version :)

>  else
> -HAS_ALTIVEC := $(shell printf '\#include \nvector int 
> a;\n' |\
> - gcc -c -x c - >&/dev/null && \
> - rm ./-.o && echo yes)
> -ifeq ($(HAS_ALTIVEC),yes)
> -OBJS += altivec1.o altivec2.o altivec4.o altivec8.o
> +  HAS_ALTIVEC := $(shell printf '\#include \nvector int a;\n' 
> |\
> +  gcc -c -x c - >/dev/null && rm ./-.o && echo yes)
> +  ifeq ($(HAS_ALTIVEC),yes)
> + CFLAGS += -I../../../arch/powerpc/include
> + CFLAGS += -DCONFIG_ALTIVEC
> + OBJS += altivec1.o altivec2.o altivec4.o altivec8.o \
> + vpermxor1.o vpermxor2.o vpermxor4.o vpermxor8.o
>  endif
>  endif
Looks like vim has replaced spaces with tabs here. Not sure how much we
care...

>  ifeq ($(ARCH),tilegx)
> @@ -97,6 +99,18 @@ altivec4.c: altivec.uc ../unroll.awk
>  altivec8.c: altivec.uc ../unroll.awk
>   $(AWK) ../unroll.awk -vN=8 < altivec.uc > $@
>
... especially seeing as tabs are already used in the file here!

> +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 > $@
>  
> + /*Q syndrome */
> + /* Check if CPU has both altivec and the vpermxor instruction*/
Very trivial nit: for future patches please make sure you have spaces
between the beginning/end of a comment and the comment.

> +# ifdef __KERNEL__
> + return (cpu_has_feature(CONFIG_ALTIVEC) &&
> + cpu_has_feature(CPU_FTR_ARCH_207S));
I think CPU_FTR_ARCH_207S implies Altivec? Again, not a real problem,
I don't think it's really worth doing a respin for any of these, so:

Reviewed-by: Daniel Axtens 

Thanks for making Power faster!

Regards,
Daniel

[v2] raid6/altivec: Add vpermxor implementation for raid6 Q syndrome

[Matt Brown]

The raid6 Q syndrome check has been optimised using the vpermxor
instruction.  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

Bugs fixed:
- A small bug in pq.h regarding a missing and mismatched
  ifdef statement
- Fixed test/Makefile to correctly build test on ppc

Signed-off-by: Matt Brown 
---
mpe I assume you are ok to take this patch, most of the other ppc raid patches 
have gone through you.

Changelog:
v2
- added reference to raid6 paper
- shortened asm lines
- removed redundant Makefile line
- fixed test/Makefile bug
---
 include/linux/raid/pq.h |   4 ++
 lib/raid6/Makefile  |  27 -
 lib/raid6/algos.c   |   4 ++
 lib/raid6/altivec.uc|   3 ++
 lib/raid6/test/Makefile |  26 +---
 lib/raid6/vpermxor.uc   | 104 
 6 files changed, 161 insertions(+), 7 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/Makefile b/lib/raid6/Makefile
index 3057011..7775aad 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[] = {
_altivec2,
_altivec4,
_altivec8,
+   _vpermxor1,
+   _vpermxor2,
+   _vpermxor4,
+   _vpermxor8,
 #endif
 #if defined(CONFIG_TILEGX)
_tilegx8,
diff --git a/lib/raid6/altivec.uc b/lib/raid6/altivec.uc
index 682aae8..d20ed0d 100644
--- a/lib/raid6/altivec.uc
+++ b/lib/raid6/altivec.uc
@@ -24,10 +24,13 @@
 
 #include 
 
+#ifdef CONFIG_ALTIVEC
+
 #include 
 #ifdef __KERNEL__
 # include 
 # include 
+#endif /* __KERNEL__ */
 
 /*
  * This is the C data type to use.  We use a vector of
diff --git a/lib/raid6/test/Makefile