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Commit ae77cbc1 authored by Ken Steele's avatar Ken Steele Committed by NeilBrown
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RAID: add tilegx SIMD implementation of raid6 

This change adds TILE-Gx SIMD instructions to the software raid
(md), modeling the Altivec implementation. This is only for Syndrome
generation; there is more that could be done to improve recovery,
as in the recent Intel SSE3 recovery implementation.

The code unrolls 8 times; this turns out to be the best on tilegx
hardware among the set 1, 2, 4, 8 or 16.  The code reads one
cache-line of data from each disk, stores P and Q then goes to the
next cache-line.

The test code in sys/linux/lib/raid6/test reports 2008 MB/s data
read rate for syndrome generation using 18 disks (16 data and 2
parity). It was 1512 MB/s before this SIMD optimizations. This is
running on 1 core with all the data in cache.

This is based on the paper The Mathematics of RAID-6.
(http://kernel.org/pub/linux/kernel/people/hpa/raid6.pdf

).

Signed-off-by: default avatarKen Steele <ken@tilera.com>
Signed-off-by: default avatarChris Metcalf <cmetcalf@tilera.com>
Signed-off-by: default avatarNeilBrown <neilb@suse.de>
parent 275c51c4

include/linux/raid/pq.h

+1 −0
Original line number Diff line number Diff line
@@ -101,6 +101,7 @@ extern const struct raid6_calls raid6_altivec8; 
extern const struct raid6_calls raid6_avx2x1;

extern const struct raid6_calls raid6_avx2x2;

extern const struct raid6_calls raid6_avx2x4;

extern const struct raid6_calls raid6_tilegx8;



struct raid6_recov_calls {

	void (*data2)(int, size_t, int, int, void **);

lib/raid6/Makefile

+6 −0
Original line number Diff line number Diff line
@@ -5,6 +5,7 @@ raid6_pq-y += algos.o recov.o tables.o int1.o int2.o int4.o \ 


raid6_pq-$(CONFIG_X86) += recov_ssse3.o recov_avx2.o mmx.o sse1.o sse2.o avx2.o

raid6_pq-$(CONFIG_ALTIVEC) += altivec1.o altivec2.o altivec4.o altivec8.o

raid6_pq-$(CONFIG_TILEGX) += tilegx8.o



hostprogs-y	+= mktables
@@ -70,6 +71,11 @@ $(obj)/altivec8.c: UNROLL := 8 
$(obj)/altivec8.c:   $(src)/altivec.uc $(src)/unroll.awk FORCE

	$(call if_changed,unroll)



targets += tilegx8.c

$(obj)/tilegx8.c:   UNROLL := 8

$(obj)/tilegx8.c:   $(src)/tilegx.uc $(src)/unroll.awk FORCE

	$(call if_changed,unroll)



quiet_cmd_mktable = TABLE   $@

      cmd_mktable = $(obj)/mktables > $@ || ( rm -f $@ && exit 1 )

lib/raid6/algos.c

+3 −0
Original line number Diff line number Diff line
@@ -65,6 +65,9 @@ const struct raid6_calls * const raid6_algos[] = { 
	&raid6_altivec2,

	&raid6_altivec4,

	&raid6_altivec8,

#endif

#if defined(CONFIG_TILEGX)

	&raid6_tilegx8,

#endif

	&raid6_intx1,

	&raid6_intx2,

lib/raid6/test/Makefile

+7 −0
Original line number Diff line number Diff line
@@ -35,6 +35,9 @@ else 
                OBJS += altivec1.o altivec2.o altivec4.o altivec8.o

        endif

endif

ifeq ($(ARCH),tilegx)

OBJS += tilegx8.o

endif



.c.o:

	$(CC) $(CFLAGS) -c -o $@ $<
@@ -85,11 +88,15 @@ int16.c: int.uc ../unroll.awk 
int32.c: int.uc ../unroll.awk

	$(AWK) ../unroll.awk -vN=32 < int.uc > $@



tilegx8.c: tilegx.uc ../unroll.awk

	$(AWK) ../unroll.awk -vN=8 < tilegx.uc > $@



tables.c: mktables

	./mktables > tables.c



clean:

	rm -f *.o *.a mktables mktables.c *.uc int*.c altivec*.c tables.c raid6test

	rm -f tilegx*.c



spotless: clean

	rm -f *~

lib/raid6/tilegx.uc

0 → 100644
+86 −0
Original line number Diff line number Diff line 
/* -*- linux-c -*- ------------------------------------------------------- *

 *

 *   Copyright 2002 H. Peter Anvin - All Rights Reserved

 *   Copyright 2012 Tilera Corporation - All Rights Reserved

 *

 *   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, Inc., 53 Temple Place Ste 330,

 *   Boston MA 02111-1307, USA; either version 2 of the License, or

 *   (at your option) any later version; incorporated herein by reference.

 *

 * ----------------------------------------------------------------------- */



/*

 * tilegx$#.c

 *

 * $#-way unrolled TILE-Gx SIMD for RAID-6 math.

 *

 * This file is postprocessed using unroll.awk.

 *

 */



#include <linux/raid/pq.h>



/* Create 8 byte copies of constant byte */

# define NBYTES(x) (__insn_v1addi(0, x))

# define NSIZE  8



/*

 * The SHLBYTE() operation shifts each byte left by 1, *not*

 * rolling over into the next byte

 */

static inline __attribute_const__ u64 SHLBYTE(u64 v)

{

	/* Vector One Byte Shift Left Immediate. */

	return __insn_v1shli(v, 1);

}



/*

 * The MASK() operation returns 0xFF in any byte for which the high

 * bit is 1, 0x00 for any byte for which the high bit is 0.

 */

static inline __attribute_const__ u64 MASK(u64 v)

{

	/* Vector One Byte Shift Right Signed Immediate. */

	return __insn_v1shrsi(v, 7);

}





void raid6_tilegx$#_gen_syndrome(int disks, size_t bytes, void **ptrs)

{

	u8 **dptr = (u8 **)ptrs;

	u64 *p, *q;

	int d, z, z0;



	u64 wd$$, wq$$, wp$$, w1$$, w2$$;

	u64 x1d = NBYTES(0x1d);

	u64 * z0ptr;



	z0 = disks - 3;			/* Highest data disk */

	p = (u64 *)dptr[z0+1];	/* XOR parity */

	q = (u64 *)dptr[z0+2];	/* RS syndrome */



	z0ptr = (u64 *)&dptr[z0][0];

	for ( d = 0 ; d < bytes ; d += NSIZE*$# ) {

		wq$$ = wp$$ = *z0ptr++;

		for ( z = z0-1 ; z >= 0 ; z-- ) {

			wd$$ = *(u64 *)&dptr[z][d+$$*NSIZE];

			wp$$ = wp$$ ^ wd$$;

			w2$$ = MASK(wq$$);

			w1$$ = SHLBYTE(wq$$);

			w2$$ = w2$$ & x1d;

			w1$$ = w1$$ ^ w2$$;

			wq$$ = w1$$ ^ wd$$;

		}

		*p++ = wp$$;

		*q++ = wq$$;

	}

}



const struct raid6_calls raid6_tilegx$# = {

	raid6_tilegx$#_gen_syndrome,

	NULL,

	"tilegx$#",

	0

};