Re: [dpdk-dev] [PATCH v3 4/8] fib: introduce AVX512 lookup

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

> Add new lookup implementation for DIR24_8 algorithm using
> AVX512 instruction set
> 
> Signed-off-by: Vladimir Medvedkin <vladimir.medvedkin@intel.com>
> ---
>  lib/librte_fib/Makefile         |  14 ++++
>  lib/librte_fib/dir24_8.c        |  24 ++++++
>  lib/librte_fib/dir24_8_avx512.c | 165 ++++++++++++++++++++++++++++++++++++++++
>  lib/librte_fib/dir24_8_avx512.h |  24 ++++++
>  lib/librte_fib/meson.build      |  11 +++
>  lib/librte_fib/rte_fib.h        |   3 +-
>  6 files changed, 240 insertions(+), 1 deletion(-)
>  create mode 100644 lib/librte_fib/dir24_8_avx512.c
>  create mode 100644 lib/librte_fib/dir24_8_avx512.h
> 
> diff --git a/lib/librte_fib/Makefile b/lib/librte_fib/Makefile
> index 1dd2a49..3958da1 100644
> --- a/lib/librte_fib/Makefile
> +++ b/lib/librte_fib/Makefile
> @@ -19,4 +19,18 @@ SRCS-$(CONFIG_RTE_LIBRTE_FIB) := rte_fib.c rte_fib6.c dir24_8.c trie.c
>  # install this header file
>  SYMLINK-$(CONFIG_RTE_LIBRTE_FIB)-include := rte_fib.h rte_fib6.h
> 
> +CC_AVX512F_SUPPORT=$(shell $(CC) -mavx512f -dM -E - </dev/null 2>&1 | \
> +grep -q __AVX512F__ && echo 1)
> +
> +CC_AVX512DQ_SUPPORT=$(shell $(CC) -mavx512dq -dM -E - </dev/null 2>&1 | \
> +grep -q __AVX512DQ__ && echo 1)
> +
> +ifeq ($(CC_AVX512F_SUPPORT), 1)
> +	ifeq ($(CC_AVX512DQ_SUPPORT), 1)
> +		SRCS-$(CONFIG_RTE_LIBRTE_FIB) += dir24_8_avx512.c
> +		CFLAGS_dir24_8_avx512.o += -mavx512f
> +		CFLAGS_dir24_8_avx512.o += -mavx512dq
> +		CFLAGS_dir24_8.o += -DCC_DIR24_8_AVX512_SUPPORT
> +	endif
> +endif
>  include $(RTE_SDK)/mk/rte.lib.mk
> diff --git a/lib/librte_fib/dir24_8.c b/lib/librte_fib/dir24_8.c
> index 9d74653..0a1c53f 100644
> --- a/lib/librte_fib/dir24_8.c
> +++ b/lib/librte_fib/dir24_8.c
> @@ -18,6 +18,12 @@
>  #include <rte_fib.h>
>  #include "dir24_8.h"
> 
> +#ifdef CC_DIR24_8_AVX512_SUPPORT
> +
> +#include "dir24_8_avx512.h"
> +
> +#endif /* CC_DIR24_8_AVX512_SUPPORT */
> +
>  #define DIR24_8_NAMESIZE	64
> 
>  #define ROUNDUP(x, y)	 RTE_ALIGN_CEIL(x, (1 << (32 - y)))
> @@ -62,6 +68,24 @@ dir24_8_get_lookup_fn(void *p, enum rte_fib_dir24_8_lookup_type type)
>  		}
>  	case RTE_FIB_DIR24_8_SCALAR_UNI:
>  		return dir24_8_lookup_bulk_uni;
> +#ifdef CC_DIR24_8_AVX512_SUPPORT
> +	case RTE_FIB_DIR24_8_VECTOR:
> +		if (rte_cpu_get_flag_enabled(RTE_CPUFLAG_AVX512F) <= 0)
> +			return NULL;
> +
> +		switch (nh_sz) {
> +		case RTE_FIB_DIR24_8_1B:
> +			return rte_dir24_8_vec_lookup_bulk_1b;
> +		case RTE_FIB_DIR24_8_2B:
> +			return rte_dir24_8_vec_lookup_bulk_2b;
> +		case RTE_FIB_DIR24_8_4B:
> +			return rte_dir24_8_vec_lookup_bulk_4b;
> +		case RTE_FIB_DIR24_8_8B:
> +			return rte_dir24_8_vec_lookup_bulk_8b;
> +		default:
> +			return NULL;
> +		}
> +#endif
>  	default:
>  		return NULL;
>  	}
> diff --git a/lib/librte_fib/dir24_8_avx512.c b/lib/librte_fib/dir24_8_avx512.c
> new file mode 100644
> index 0000000..43dba28
> --- /dev/null
> +++ b/lib/librte_fib/dir24_8_avx512.c
> @@ -0,0 +1,165 @@
> +/* SPDX-License-Identifier: BSD-3-Clause
> + * Copyright(c) 2020 Intel Corporation
> + */
> +
> +#include <rte_vect.h>
> +#include <rte_fib.h>
> +
> +#include "dir24_8.h"
> +#include "dir24_8_avx512.h"
> +
> +static __rte_always_inline void
> +dir24_8_vec_lookup_x16(void *p, const uint32_t *ips,
> +	uint64_t *next_hops, int size)
> +{
> +	struct dir24_8_tbl *dp = (struct dir24_8_tbl *)p;
> +	__mmask16 msk_ext;
> +	__mmask16 exp_msk = 0x5555;
> +	__m512i ip_vec, idxes, res, bytes;
> +	const __m512i zero = _mm512_set1_epi32(0);
> +	const __m512i lsb = _mm512_set1_epi32(1);
> +	const __m512i lsbyte_msk = _mm512_set1_epi32(0xff);
> +	__m512i tmp1, tmp2, res_msk;
> +	__m256i tmp256;
> +	/* used to mask gather values if size is 1/2 (8/16 bit next hops) */
> +	if (size == sizeof(uint8_t))
> +		res_msk = _mm512_set1_epi32(UINT8_MAX);
> +	else if (size == sizeof(uint16_t))
> +		res_msk = _mm512_set1_epi32(UINT16_MAX);
> +
> +	ip_vec = _mm512_loadu_si512(ips);
> +	/* mask 24 most significant bits */
> +	idxes = _mm512_srli_epi32(ip_vec, 8);
> +
> +	/**
> +	 * lookup in tbl24
> +	 * Put it inside branch to make compiler happy with -O0
> +	 */
> +	if (size == sizeof(uint8_t)) {
> +		res = _mm512_i32gather_epi32(idxes, (const int *)dp->tbl24, 1);
> +		res = _mm512_and_epi32(res, res_msk);
> +	} else if (size == sizeof(uint16_t)) {
> +		res = _mm512_i32gather_epi32(idxes, (const int *)dp->tbl24, 2);
> +		res = _mm512_and_epi32(res, res_msk);
> +	} else
> +		res = _mm512_i32gather_epi32(idxes, (const int *)dp->tbl24, 4);
> +
> +	/* get extended entries indexes */
> +	msk_ext = _mm512_test_epi32_mask(res, lsb);
> +
> +	if (msk_ext != 0) {
> +		idxes = _mm512_srli_epi32(res, 1);
> +		idxes = _mm512_slli_epi32(idxes, 8);
> +		bytes = _mm512_and_epi32(ip_vec, lsbyte_msk);
> +		idxes = _mm512_maskz_add_epi32(msk_ext, idxes, bytes);
> +		if (size == sizeof(uint8_t)) {
> +			idxes = _mm512_mask_i32gather_epi32(zero, msk_ext,
> +				idxes, (const int *)dp->tbl8, 1);
> +			idxes = _mm512_and_epi32(idxes, res_msk);
> +		} else if (size == sizeof(uint16_t)) {
> +			idxes = _mm512_mask_i32gather_epi32(zero, msk_ext,
> +				idxes, (const int *)dp->tbl8, 2);
> +			idxes = _mm512_and_epi32(idxes, res_msk);
> +		} else
> +			idxes = _mm512_mask_i32gather_epi32(zero, msk_ext,
> +				idxes, (const int *)dp->tbl8, 4);
> +
> +		res = _mm512_mask_blend_epi32(msk_ext, res, idxes);
> +	}
> +
> +	res = _mm512_srli_epi32(res, 1);
> +	tmp1 = _mm512_maskz_expand_epi32(exp_msk, res);
> +	tmp256 = _mm512_extracti32x8_epi32(res, 1);
> +	tmp2 = _mm512_maskz_expand_epi32(exp_msk,
> +		_mm512_castsi256_si512(tmp256));
> +	_mm512_storeu_si512(next_hops, tmp1);
> +	_mm512_storeu_si512(next_hops + 8, tmp2);
> +}
> +
> +static __rte_always_inline void
> +dir24_8_vec_lookup_x8_8b(void *p, const uint32_t *ips,
> +	uint64_t *next_hops)
> +{
> +	struct dir24_8_tbl *dp = (struct dir24_8_tbl *)p;
> +	const __m512i zero = _mm512_set1_epi32(0);
> +	const __m512i lsbyte_msk = _mm512_set1_epi64(0xff);
> +	const __m512i lsb = _mm512_set1_epi64(1);
> +	__m512i res, idxes, bytes;
> +	__m256i idxes_256, ip_vec;
> +	__mmask8 msk_ext;
> +
> +	ip_vec = _mm256_loadu_si256((const void *)ips);
> +	/* mask 24 most significant bits */
> +	idxes_256 = _mm256_srli_epi32(ip_vec, 8);
> +
> +	/* lookup in tbl24 */
> +	res = _mm512_i32gather_epi64(idxes_256, (const void *)dp->tbl24, 8);
> +
> +	/* get extended entries indexes */
> +	msk_ext = _mm512_test_epi64_mask(res, lsb);
> +
> +	if (msk_ext != 0) {
> +		bytes = _mm512_cvtepi32_epi64(ip_vec);
> +		idxes = _mm512_srli_epi64(res, 1);
> +		idxes = _mm512_slli_epi64(idxes, 8);
> +		bytes = _mm512_and_epi64(bytes, lsbyte_msk);
> +		idxes = _mm512_maskz_add_epi64(msk_ext, idxes, bytes);
> +		idxes = _mm512_mask_i64gather_epi64(zero, msk_ext, idxes,
> +			(const void *)dp->tbl8, 8);
> +
> +		res = _mm512_mask_blend_epi64(msk_ext, res, idxes);
> +	}
> +
> +	res = _mm512_srli_epi64(res, 1);
> +	_mm512_storeu_si512(next_hops, res);
> +}
> +
> +void
> +rte_dir24_8_vec_lookup_bulk_1b(void *p, const uint32_t *ips,
> +	uint64_t *next_hops, const unsigned int n)
> +{
> +	uint32_t i;
> +	for (i = 0; i < (n / 16); i++)
> +		dir24_8_vec_lookup_x16(p, ips + i * 16, next_hops + i * 16,
> +			sizeof(uint8_t));
> +

Just curious: if for reminder, instead of calling scalar lookup,
Introduce a masked version of avx512 lookup - would it be slower?

> +	dir24_8_lookup_bulk_1b(p, ips + i * 16, next_hops + i * 16,
> +		n - i * 16);
> +}
> +
> +void
> +rte_dir24_8_vec_lookup_bulk_2b(void *p, const uint32_t *ips,
> +	uint64_t *next_hops, const unsigned int n)
> +{
> +	uint32_t i;
> +	for (i = 0; i < (n / 16); i++)
> +		dir24_8_vec_lookup_x16(p, ips + i * 16, next_hops + i * 16,
> +			sizeof(uint16_t));
> +
> +	dir24_8_lookup_bulk_2b(p, ips + i * 16, next_hops + i * 16,
> +		n - i * 16);
> +}
> +
> +void
> +rte_dir24_8_vec_lookup_bulk_4b(void *p, const uint32_t *ips,
> +	uint64_t *next_hops, const unsigned int n)
> +{
> +	uint32_t i;
> +	for (i = 0; i < (n / 16); i++)
> +		dir24_8_vec_lookup_x16(p, ips + i * 16, next_hops + i * 16,
> +			sizeof(uint32_t));
> +
> +	dir24_8_lookup_bulk_4b(p, ips + i * 16, next_hops + i * 16,
> +		n - i * 16);
> +}
> +
> +void
> +rte_dir24_8_vec_lookup_bulk_8b(void *p, const uint32_t *ips,
> +	uint64_t *next_hops, const unsigned int n)
> +{
> +	uint32_t i;
> +	for (i = 0; i < (n / 8); i++)
> +		dir24_8_vec_lookup_x8_8b(p, ips + i * 8, next_hops + i * 8);
> +
> +	dir24_8_lookup_bulk_8b(p, ips + i * 8, next_hops + i * 8, n - i * 8);
> +}
> diff --git a/lib/librte_fib/dir24_8_avx512.h b/lib/librte_fib/dir24_8_avx512.h
> new file mode 100644
> index 0000000..1d3c2b9
> --- /dev/null
> +++ b/lib/librte_fib/dir24_8_avx512.h
> @@ -0,0 +1,24 @@
> +/* SPDX-License-Identifier: BSD-3-Clause
> + * Copyright(c) 2020 Intel Corporation
> + */
> +
> +#ifndef _DIR248_AVX512_H_
> +#define _DIR248_AVX512_H_
> +
> +void
> +rte_dir24_8_vec_lookup_bulk_1b(void *p, const uint32_t *ips,
> +	uint64_t *next_hops, const unsigned int n);
> +
> +void
> +rte_dir24_8_vec_lookup_bulk_2b(void *p, const uint32_t *ips,
> +	uint64_t *next_hops, const unsigned int n);
> +
> +void
> +rte_dir24_8_vec_lookup_bulk_4b(void *p, const uint32_t *ips,
> +	uint64_t *next_hops, const unsigned int n);
> +
> +void
> +rte_dir24_8_vec_lookup_bulk_8b(void *p, const uint32_t *ips,
> +	uint64_t *next_hops, const unsigned int n);
> +
> +#endif /* _DIR248_AVX512_H_ */
> diff --git a/lib/librte_fib/meson.build b/lib/librte_fib/meson.build
> index 771828f..0963f3c 100644
> --- a/lib/librte_fib/meson.build
> +++ b/lib/librte_fib/meson.build
> @@ -5,3 +5,14 @@
>  sources = files('rte_fib.c', 'rte_fib6.c', 'dir24_8.c', 'trie.c')
>  headers = files('rte_fib.h', 'rte_fib6.h')
>  deps += ['rib']
> +
> +if dpdk_conf.has('RTE_ARCH_X86') and cc.has_argument('-mavx512f')
> +	if cc.has_argument('-mavx512dq')
> +		dir24_8_avx512_tmp = static_library('dir24_8_avx512_tmp',
> +			'dir24_8_avx512.c',
> +			dependencies: static_rte_eal,
> +			c_args: cflags + ['-mavx512f'] + ['-mavx512dq'])
> +		objs += dir24_8_avx512_tmp.extract_objects('dir24_8_avx512.c')
> +		cflags += '-DCC_DIR24_8_AVX512_SUPPORT'
> +	endif
> +endif
> diff --git a/lib/librte_fib/rte_fib.h b/lib/librte_fib/rte_fib.h
> index db35685..2919d13 100644
> --- a/lib/librte_fib/rte_fib.h
> +++ b/lib/librte_fib/rte_fib.h
> @@ -54,7 +54,8 @@ enum rte_fib_dir24_8_nh_sz {
>  enum rte_fib_dir24_8_lookup_type {
>  	RTE_FIB_DIR24_8_SCALAR_MACRO,
>  	RTE_FIB_DIR24_8_SCALAR_INLINE,
> -	RTE_FIB_DIR24_8_SCALAR_UNI
> +	RTE_FIB_DIR24_8_SCALAR_UNI,
> +	RTE_FIB_DIR24_8_VECTOR
>  };
> 
>  /** FIB configuration structure */
> --

Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>

> 2.7.4