RE: [PATCH v7 1/4] hash: pack the hitmask for hash in bulk lookup

[Konstantin Ananyev <konstantin.ananyev@huawei.com>]

Hi,

> Current hitmask includes padding due to Intel's SIMD
> implementation detail. This patch allows non Intel SIMD
> implementations to benefit from a dense hitmask.
> In addition, the new dense hitmask interweave the primary
> and secondary matches which allow a better cache usage and
> enable future improvements for the SIMD implementations
> 
> Signed-off-by: Yoan Picchi <yoan.picchi@arm.com>
> Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> Reviewed-by: Nathan Brown <nathan.brown@arm.com>
> ---
>  .mailmap                                  |   2 +
>  lib/hash/arch/arm/compare_signatures.h    |  61 +++++++
>  lib/hash/arch/common/compare_signatures.h |  38 +++++
>  lib/hash/arch/x86/compare_signatures.h    |  53 ++++++
>  lib/hash/rte_cuckoo_hash.c                | 192 ++++++++++++----------
>  5 files changed, 255 insertions(+), 91 deletions(-)
>  create mode 100644 lib/hash/arch/arm/compare_signatures.h
>  create mode 100644 lib/hash/arch/common/compare_signatures.h
>  create mode 100644 lib/hash/arch/x86/compare_signatures.h
> 
> diff --git a/.mailmap b/.mailmap
> index 66ebc20666..00b50414d3 100644
> --- a/.mailmap
> +++ b/.mailmap
> @@ -494,6 +494,7 @@ Hari Kumar Vemula <hari.kumarx.vemula@intel.com>
>  Harini Ramakrishnan <harini.ramakrishnan@microsoft.com>
>  Hariprasad Govindharajan <hariprasad.govindharajan@intel.com>
>  Harish Patil <harish.patil@cavium.com> <harish.patil@qlogic.com>
> +Harjot Singh <harjot.singh@arm.com>
>  Harman Kalra <hkalra@marvell.com>
>  Harneet Singh <harneet.singh@intel.com>
>  Harold Huang <baymaxhuang@gmail.com>
> @@ -1633,6 +1634,7 @@ Yixue Wang <yixue.wang@intel.com>
>  Yi Yang <yangyi01@inspur.com> <yi.y.yang@intel.com>
>  Yi Zhang <zhang.yi75@zte.com.cn>
>  Yoann Desmouceaux <ydesmouc@cisco.com>
> +Yoan Picchi <yoan.picchi@arm.com>
>  Yogesh Jangra <yogesh.jangra@intel.com>
>  Yogev Chaimovich <yogev@cgstowernetworks.com>
>  Yongjie Gu <yongjiex.gu@intel.com>
> diff --git a/lib/hash/arch/arm/compare_signatures.h b/lib/hash/arch/arm/compare_signatures.h
> new file mode 100644
> index 0000000000..1af6ba8190
> --- /dev/null
> +++ b/lib/hash/arch/arm/compare_signatures.h
> @@ -0,0 +1,61 @@
> +/* SPDX-License-Identifier: BSD-3-Clause
> + * Copyright(c) 2010-2016 Intel Corporation
> + * Copyright(c) 2018-2024 Arm Limited
> + */
> +
> +/*
> + * Arm's version uses a densely packed hitmask buffer:
> + * Every bit is in use.
> + */
> +
> +#include <inttypes.h>
> +#include <rte_common.h>
> +#include <rte_vect.h>
> +#include "rte_cuckoo_hash.h"
> +
> +#define DENSE_HASH_BULK_LOOKUP 1
> +
> +static inline void
> +compare_signatures_dense(uint16_t *hitmask_buffer,
> +			const uint16_t *prim_bucket_sigs,
> +			const uint16_t *sec_bucket_sigs,
> +			uint16_t sig,
> +			enum rte_hash_sig_compare_function sig_cmp_fn)
> +{
> +
> +	static_assert(sizeof(*hitmask_buffer) >= 2*(RTE_HASH_BUCKET_ENTRIES/8),
> +	"The hitmask must be exactly wide enough to accept the whole hitmask if it is dense");
> +
> +	/* For match mask every bits indicates the match */
> +	switch (sig_cmp_fn) {
> +#if RTE_HASH_BUCKET_ENTRIES <= 8
> +	case RTE_HASH_COMPARE_NEON: {
> +		uint16x8_t vmat, vsig, x;
> +		int16x8_t shift = {0, 1, 2, 3, 4, 5, 6, 7};
> +		uint16_t low, high;
> +
> +		vsig = vld1q_dup_u16((uint16_t const *)&sig);
> +		/* Compare all signatures in the primary bucket */
> +		vmat = vceqq_u16(vsig,
> +			vld1q_u16((uint16_t const *)prim_bucket_sigs));
> +		x = vshlq_u16(vandq_u16(vmat, vdupq_n_u16(0x0001)), shift);
> +		low = (uint16_t)(vaddvq_u16(x));
> +		/* Compare all signatures in the secondary bucket */
> +		vmat = vceqq_u16(vsig,
> +			vld1q_u16((uint16_t const *)sec_bucket_sigs));
> +		x = vshlq_u16(vandq_u16(vmat, vdupq_n_u16(0x0001)), shift);
> +		high = (uint16_t)(vaddvq_u16(x));
> +		*hitmask_buffer = low | high << RTE_HASH_BUCKET_ENTRIES;
> +
> +		}
> +		break;
> +#endif
> +	default:
> +		for (unsigned int i = 0; i < RTE_HASH_BUCKET_ENTRIES; i++) {
> +			*hitmask_buffer |=
> +				((sig == prim_bucket_sigs[i]) << i);
> +			*hitmask_buffer |=
> +				((sig == sec_bucket_sigs[i]) << i) << RTE_HASH_BUCKET_ENTRIES;
> +		}
> +	}
> +}
> diff --git a/lib/hash/arch/common/compare_signatures.h b/lib/hash/arch/common/compare_signatures.h
> new file mode 100644
> index 0000000000..dcf9444032
> --- /dev/null
> +++ b/lib/hash/arch/common/compare_signatures.h
> @@ -0,0 +1,38 @@
> +/* SPDX-License-Identifier: BSD-3-Clause
> + * Copyright(c) 2010-2016 Intel Corporation
> + * Copyright(c) 2018-2024 Arm Limited
> + */
> +
> +/*
> + * The generic version could use either a dense or sparsely packed hitmask buffer,
> + * but the dense one is slightly faster.
> + */
> +
> +#include <inttypes.h>
> +#include <rte_common.h>
> +#include <rte_vect.h>
> +#include "rte_cuckoo_hash.h"
> +
> +#define DENSE_HASH_BULK_LOOKUP 1
> +
> +static inline void
> +compare_signatures_dense(uint16_t *hitmask_buffer,
> +			const uint16_t *prim_bucket_sigs,
> +			const uint16_t *sec_bucket_sigs,
> +			uint16_t sig,
> +			enum rte_hash_sig_compare_function sig_cmp_fn)
> +{
> +	(void) sig_cmp_fn;
> +
> +	static_assert(sizeof(*hitmask_buffer) >= 2*(RTE_HASH_BUCKET_ENTRIES/8),
> +	"The hitmask must be exactly wide enough to accept the whole hitmask if it is dense");
> +
> +	/* For match mask every bits indicates the match */
> +	for (unsigned int i = 0; i < RTE_HASH_BUCKET_ENTRIES; i++) {
> +		*hitmask_buffer |=
> +			((sig == prim_bucket_sigs[i]) << i);
> +		*hitmask_buffer |=
> +			((sig == sec_bucket_sigs[i]) << i) << RTE_HASH_BUCKET_ENTRIES;
> +	}
> +
> +}

Thanks for re-factoring compare_signatures_...() code, it looks much cleaner that way.
One question I have - does it mean that now for x86 we always use 'sparse' while for all other
ARM and non-ARM platforms we switch to 'dense'?

> diff --git a/lib/hash/arch/x86/compare_signatures.h b/lib/hash/arch/x86/compare_signatures.h
> new file mode 100644
> index 0000000000..7eec499e1f
> --- /dev/null
> +++ b/lib/hash/arch/x86/compare_signatures.h
> @@ -0,0 +1,53 @@
> +/* SPDX-License-Identifier: BSD-3-Clause
> + * Copyright(c) 2010-2016 Intel Corporation
> + * Copyright(c) 2018-2024 Arm Limited
> + */
> +
> +/*
> + * x86's version uses a sparsely packed hitmask buffer:
> + * Every other bit is padding.
> + */
> +
> +#include <inttypes.h>
> +#include <rte_common.h>
> +#include <rte_vect.h>
> +#include "rte_cuckoo_hash.h"
> +
> +#define DENSE_HASH_BULK_LOOKUP 0
> +
> +static inline void
> +compare_signatures_sparse(uint32_t *prim_hash_matches, uint32_t *sec_hash_matches,
> +			const struct rte_hash_bucket *prim_bkt,
> +			const struct rte_hash_bucket *sec_bkt,
> +			uint16_t sig,
> +			enum rte_hash_sig_compare_function sig_cmp_fn)
> +{
> +	/* For match mask the first bit of every two bits indicates the match */
> +	switch (sig_cmp_fn) {
> +#if defined(__SSE2__) && RTE_HASH_BUCKET_ENTRIES <= 8
> +	case RTE_HASH_COMPARE_SSE:
> +		/* Compare all signatures in the bucket */
> +		*prim_hash_matches = _mm_movemask_epi8(_mm_cmpeq_epi16(
> +				_mm_load_si128(
> +					(__m128i const *)prim_bkt->sig_current),
> +				_mm_set1_epi16(sig)));
> +		/* Extract the even-index bits only */
> +		*prim_hash_matches &= 0x5555;
> +		/* Compare all signatures in the bucket */
> +		*sec_hash_matches = _mm_movemask_epi8(_mm_cmpeq_epi16(
> +				_mm_load_si128(
> +					(__m128i const *)sec_bkt->sig_current),
> +				_mm_set1_epi16(sig)));
> +		/* Extract the even-index bits only */
> +		*sec_hash_matches &= 0x5555;
> +		break;
> +#endif /* defined(__SSE2__) */
> +	default:
> +		for (unsigned int i = 0; i < RTE_HASH_BUCKET_ENTRIES; i++) {
> +			*prim_hash_matches |=
> +				((sig == prim_bkt->sig_current[i]) << (i << 1));
> +			*sec_hash_matches |=
> +				((sig == sec_bkt->sig_current[i]) << (i << 1));
> +		}
> +	}
> +}