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Fletcher4 algorithm implemented in pure NEON for Aarch64 / ARMv8 64 bits

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This is not useful on micro-architecture with a weak NEON
implementation (only 64 bits); the native version is slower &
the byteswap barely faster than scalar.  On A53 or A57, it's
a small improvement on scalar but OK for byteswap.

Results from an A53 system:
0 0 0x01 -1 0 1499068294333000 1499101101878000
implementation   native         byteswap       
scalar           1008227510     755880264      
aarch64_neon     1198098720     1044818671     
fastest          aarch64_neon   aarch64_neon 

Results from a A57 system:
0 0 0x01 -1 0 4407214734807033 4407233933777404
implementation   native         byteswap       
scalar           2302071241     1124873346     
aarch64_neon     2542214946     2245570352     
fastest          aarch64_neon   aarch64_neon 

Reviewed-by: Gvozden Neskovic <neskovic@gmail.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Romain Dolbeau <romain.dolbeau@atos.net>
Closes #5248
This commit is contained in:
Romain Dolbeau 2016-10-21 19:55:49 +02:00 committed by Brian Behlendorf
parent e4ffa98dca
commit 24cdeaf12e
6 changed files with 232 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
include/zfs_fletcher.h
View File

@ -77,6 +77,10 @@ typedef struct zfs_fletcher_avx512 {
uint64_t v[8] __attribute__((aligned(64)));
} zfs_fletcher_avx512_t;
typedef struct zfs_fletcher_aarch64_neon {
uint64_t v[2] __attribute__((aligned(16)));
} zfs_fletcher_aarch64_neon_t;
typedef union fletcher_4_ctx {
zio_cksum_t scalar;
@ -90,6 +94,9 @@ typedef union fletcher_4_ctx {
#if defined(__x86_64) && defined(HAVE_AVX512F)
zfs_fletcher_avx512_t avx512[4];
#endif
#if defined(__aarch64__)
zfs_fletcher_aarch64_neon_t aarch64_neon[4];
#endif
} fletcher_4_ctx_t;
/*
@ -128,6 +135,10 @@ extern const fletcher_4_ops_t fletcher_4_avx2_ops;
extern const fletcher_4_ops_t fletcher_4_avx512f_ops;
#endif
#if defined(__aarch64__)
extern const fletcher_4_ops_t fletcher_4_aarch64_neon_ops;
#endif
#ifdef __cplusplus
}
#endif

1
lib/libzpool/Makefile.am
View File

@ -25,6 +25,7 @@ KERNEL_C = \
zfs_fletcher_intel.c \
zfs_fletcher_sse.c \
zfs_fletcher_avx512.c \
zfs_fletcher_aarch64_neon.c \
zfs_namecheck.c \
zfs_prop.c \
zfs_uio.c \

2
man/man5/zfs-module-parameters.5
View File

@ -900,7 +900,7 @@ Default value: \fB67,108,864\fR.
Select a fletcher 4 implementation.
.sp
Supported selectors are: \fBfastest\fR, \fBscalar\fR, \fBsse2\fR, \fBssse3\fR,
\fBavx2\fR, and \fBavx512f\fR.
\fBavx2\fR, \fBavx512f\fR, and \fBaarch64_neon\fR.
All of the selectors except \fBfastest\fR and \fBscalar\fR require instruction
set extensions to be available and will only appear if ZFS detects that they are
present at runtime. If multiple implementations of fletcher 4 are available,

1
module/zcommon/Makefile.in
View File

@ -19,3 +19,4 @@ $(MODULE)-objs += zpool_prop.o
$(MODULE)-$(CONFIG_X86) += zfs_fletcher_intel.o
$(MODULE)-$(CONFIG_X86) += zfs_fletcher_sse.o
$(MODULE)-$(CONFIG_X86) += zfs_fletcher_avx512.o
$(MODULE)-$(CONFIG_ARM64) += zfs_fletcher_aarch64_neon.o

3
module/zcommon/zfs_fletcher.c
View File

@ -176,6 +176,9 @@ static const fletcher_4_ops_t *fletcher_4_impls[] = {
#if defined(__x86_64) && defined(HAVE_AVX512F)
&fletcher_4_avx512f_ops,
#endif
#if defined(__aarch64__)
&fletcher_4_aarch64_neon_ops,
#endif
};
/* Hold all supported implementations */

215
module/zcommon/zfs_fletcher_aarch64_neon.c Normal file
View File

@ -0,0 +1,215 @@
/*
* Implement fast Fletcher4 with NEON instructions. (aarch64)
*
* Use the 128-bit NEON SIMD instructions and registers to compute
* Fletcher4 in four incremental 64-bit parallel accumulator streams,
* and then combine the streams to form the final four checksum words.
* This implementation is a derivative of the AVX SIMD implementation by
* James Guilford and Jinshan Xiong from Intel (see zfs_fletcher_intel.c).
*
* Copyright (C) 2016 Romain Dolbeau.
*
* Authors:
* Romain Dolbeau <romain.dolbeau@atos.net>
*
* This software is available to you under a choice of one of two
* licenses. You may choose to be licensed under the terms of the GNU
* General Public License (GPL) Version 2, available from the file
* COPYING in the main directory of this source tree, or the
* OpenIB.org BSD license below:
*
* Redistribution and use in source and binary forms, with or
* without modification, are permitted provided that the following
* conditions are met:
*
* - Redistributions of source code must retain the above
* copyright notice, this list of conditions and the following
* disclaimer.
*
* - Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials
* provided with the distribution.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#if defined(__aarch64__)
#include <linux/simd_aarch64.h>
#include <sys/spa_checksum.h>
#include <zfs_fletcher.h>
#include <strings.h>
static void
fletcher_4_aarch64_neon_init(fletcher_4_ctx_t *ctx)
{
bzero(ctx->aarch64_neon, 4 * sizeof (zfs_fletcher_aarch64_neon_t));
}
static void
fletcher_4_aarch64_neon_fini(fletcher_4_ctx_t *ctx, zio_cksum_t *zcp)
{
uint64_t A, B, C, D;
A = ctx->aarch64_neon[0].v[0] + ctx->aarch64_neon[0].v[1];
B = 2 * ctx->aarch64_neon[1].v[0] + 2 * ctx->aarch64_neon[1].v[1] -
ctx->aarch64_neon[0].v[1];
C = 4 * ctx->aarch64_neon[2].v[0] - ctx->aarch64_neon[1].v[0] +
4 * ctx->aarch64_neon[2].v[1] - 3 * ctx->aarch64_neon[1].v[1];
D = 8 * ctx->aarch64_neon[3].v[0] - 4 * ctx->aarch64_neon[2].v[0] +
8 * ctx->aarch64_neon[3].v[1] - 8 * ctx->aarch64_neon[2].v[1] +
ctx->aarch64_neon[1].v[1];
ZIO_SET_CHECKSUM(zcp, A, B, C, D);
}
#define NEON_INIT_LOOP() \
asm("eor %[ZERO].16b,%[ZERO].16b,%[ZERO].16b\n" \
"ld1 { %[ACC0].4s }, %[CTX0]\n" \
"ld1 { %[ACC1].4s }, %[CTX1]\n" \
"ld1 { %[ACC2].4s }, %[CTX2]\n" \
"ld1 { %[ACC3].4s }, %[CTX3]\n" \
: [ZERO] "=w" (ZERO), \
[ACC0] "=w" (ACC0), [ACC1] "=w" (ACC1), \
[ACC2] "=w" (ACC2), [ACC3] "=w" (ACC3) \
: [CTX0] "Q" (ctx->aarch64_neon[0]), \
[CTX1] "Q" (ctx->aarch64_neon[1]), \
[CTX2] "Q" (ctx->aarch64_neon[2]), \
[CTX3] "Q" (ctx->aarch64_neon[3]))
#define NEON_DO_REVERSE "rev32 %[SRC].16b, %[SRC].16b\n"
#define NEON_DONT_REVERSE ""
#define NEON_MAIN_LOOP(REVERSE) \
asm("ld1 { %[SRC].4s }, %[IP]\n" \
REVERSE \
"zip1 %[TMP1].4s, %[SRC].4s, %[ZERO].4s\n" \
"zip2 %[TMP2].4s, %[SRC].4s, %[ZERO].4s\n" \
"add %[ACC0].2d, %[ACC0].2d, %[TMP1].2d\n" \
"add %[ACC1].2d, %[ACC1].2d, %[ACC0].2d\n" \
"add %[ACC2].2d, %[ACC2].2d, %[ACC1].2d\n" \
"add %[ACC3].2d, %[ACC3].2d, %[ACC2].2d\n" \
"add %[ACC0].2d, %[ACC0].2d, %[TMP2].2d\n" \
"add %[ACC1].2d, %[ACC1].2d, %[ACC0].2d\n" \
"add %[ACC2].2d, %[ACC2].2d, %[ACC1].2d\n" \
"add %[ACC3].2d, %[ACC3].2d, %[ACC2].2d\n" \
: [SRC] "=&w" (SRC), \
[TMP1] "=&w" (TMP1), [TMP2] "=&w" (TMP2), \
[ACC0] "+w" (ACC0), [ACC1] "+w" (ACC1), \
[ACC2] "+w" (ACC2), [ACC3] "+w" (ACC3) \
: [ZERO] "w" (ZERO), [IP] "Q" (*ip))
#define NEON_FINI_LOOP() \
asm("st1 { %[ACC0].4s },%[DST0]\n" \
"st1 { %[ACC1].4s },%[DST1]\n" \
"st1 { %[ACC2].4s },%[DST2]\n" \
"st1 { %[ACC3].4s },%[DST3]\n" \
: [DST0] "=Q" (ctx->aarch64_neon[0]), \
[DST1] "=Q" (ctx->aarch64_neon[1]), \
[DST2] "=Q" (ctx->aarch64_neon[2]), \
[DST3] "=Q" (ctx->aarch64_neon[3]) \
: [ACC0] "w" (ACC0), [ACC1] "w" (ACC1), \
[ACC2] "w" (ACC2), [ACC3] "w" (ACC3))
static void
fletcher_4_aarch64_neon_native(fletcher_4_ctx_t *ctx,
const void *buf, uint64_t size)
{
const uint64_t *ip = buf;
const uint64_t *ipend = (uint64_t *)((uint8_t *)ip + size);
#if defined(_KERNEL)
register unsigned char ZERO asm("v0") __attribute__((vector_size(16)));
register unsigned char ACC0 asm("v1") __attribute__((vector_size(16)));
register unsigned char ACC1 asm("v2") __attribute__((vector_size(16)));
register unsigned char ACC2 asm("v3") __attribute__((vector_size(16)));
register unsigned char ACC3 asm("v4") __attribute__((vector_size(16)));
register unsigned char TMP1 asm("v5") __attribute__((vector_size(16)));
register unsigned char TMP2 asm("v6") __attribute__((vector_size(16)));
register unsigned char SRC asm("v7") __attribute__((vector_size(16)));
#else
unsigned char ZERO __attribute__((vector_size(16)));
unsigned char ACC0 __attribute__((vector_size(16)));
unsigned char ACC1 __attribute__((vector_size(16)));
unsigned char ACC2 __attribute__((vector_size(16)));
unsigned char ACC3 __attribute__((vector_size(16)));
unsigned char TMP1 __attribute__((vector_size(16)));
unsigned char TMP2 __attribute__((vector_size(16)));
unsigned char SRC __attribute__((vector_size(16)));
#endif
kfpu_begin();
NEON_INIT_LOOP();
for (; ip < ipend; ip += 2) {
NEON_MAIN_LOOP(NEON_DONT_REVERSE);
}
NEON_FINI_LOOP();
kfpu_end();
}
static void
fletcher_4_aarch64_neon_byteswap(fletcher_4_ctx_t *ctx,
const void *buf, uint64_t size)
{
const uint64_t *ip = buf;
const uint64_t *ipend = (uint64_t *)((uint8_t *)ip + size);
#if defined(_KERNEL)
register unsigned char ZERO asm("v0") __attribute__((vector_size(16)));
register unsigned char ACC0 asm("v1") __attribute__((vector_size(16)));
register unsigned char ACC1 asm("v2") __attribute__((vector_size(16)));
register unsigned char ACC2 asm("v3") __attribute__((vector_size(16)));
register unsigned char ACC3 asm("v4") __attribute__((vector_size(16)));
register unsigned char TMP1 asm("v5") __attribute__((vector_size(16)));
register unsigned char TMP2 asm("v6") __attribute__((vector_size(16)));
register unsigned char SRC asm("v7") __attribute__((vector_size(16)));
#else
unsigned char ZERO __attribute__((vector_size(16)));
unsigned char ACC0 __attribute__((vector_size(16)));
unsigned char ACC1 __attribute__((vector_size(16)));
unsigned char ACC2 __attribute__((vector_size(16)));
unsigned char ACC3 __attribute__((vector_size(16)));
unsigned char TMP1 __attribute__((vector_size(16)));
unsigned char TMP2 __attribute__((vector_size(16)));
unsigned char SRC __attribute__((vector_size(16)));
#endif
kfpu_begin();
NEON_INIT_LOOP();
for (; ip < ipend; ip += 2) {
NEON_MAIN_LOOP(NEON_DO_REVERSE);
}
NEON_FINI_LOOP();
kfpu_end();
}
static boolean_t fletcher_4_aarch64_neon_valid(void)
{
return (B_TRUE);
}
const fletcher_4_ops_t fletcher_4_aarch64_neon_ops = {
.init_native = fletcher_4_aarch64_neon_init,
.compute_native = fletcher_4_aarch64_neon_native,
.fini_native = fletcher_4_aarch64_neon_fini,
.init_byteswap = fletcher_4_aarch64_neon_init,
.compute_byteswap = fletcher_4_aarch64_neon_byteswap,
.fini_byteswap = fletcher_4_aarch64_neon_fini,
.valid = fletcher_4_aarch64_neon_valid,
.name = "aarch64_neon"
};
#endif /* defined(__aarch64__) */