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mirror_zfs/module/zcommon/zfs_fletcher_aarch64_neon.c
Richard Yao 59493b63c1
Micro-optimize fletcher4 calculations 
When processing abds, we execute 1 `kfpu_begin()`/`kfpu_end()` pair on
every page in the abd. This is wasteful and slows down checksum
performance versus what the benchmark claimed. We correct this by moving
those calls to the init and fini functions.

Also, we always check the buffer length against 0 before calling the
non-scalar checksum functions. This means that we do not need to execute
the loop condition for the first loop iteration. That allows us to
micro-optimize the checksum calculations by switching to do-while loops.

Note that we do not apply that micro-optimization to the scalar
implementation because there is no check in
`fletcher_4_incremental_native()`/`fletcher_4_incremental_byteswap()`
against 0 sized buffers being passed.

Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Closes #14247
2022-12-05 11:00:34 -08:00

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/*
* Implement fast Fletcher4 with NEON instructions. (aarch64)
*
* Use the 128-bit NEON SIMD instructions and registers to compute
* Fletcher4 in two 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 <sys/simd.h>
#include <sys/spa_checksum.h>
#include <sys/string.h>
#include <zfs_fletcher.h>
ZFS_NO_SANITIZE_UNDEFINED
static void
fletcher_4_aarch64_neon_init(fletcher_4_ctx_t *ctx)
{
kfpu_begin();
memset(ctx->aarch64_neon, 0, 4 * sizeof (zfs_fletcher_aarch64_neon_t));
}
ZFS_NO_SANITIZE_UNDEFINED
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);
kfpu_end();
}
#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
NEON_INIT_LOOP();
do {
NEON_MAIN_LOOP(NEON_DONT_REVERSE);
} while ((ip += 2) < ipend);
NEON_FINI_LOOP();
}
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
NEON_INIT_LOOP();
do {
NEON_MAIN_LOOP(NEON_DO_REVERSE);
} while ((ip += 2) < ipend);
NEON_FINI_LOOP();
}
static boolean_t fletcher_4_aarch64_neon_valid(void)
{
return (kfpu_allowed());
}
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__) */
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