Hello Yoan,
On Wed, Jul 3, 2024 at 7:13 PM Yoan Picchi <yoan.pic...@arm.com> wrote:
>
> 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
> The default non SIMD path now use this dense mask.
>
> Signed-off-by: Yoan Picchi <yoan.pic...@arm.com>
> Reviewed-by: Ruifeng Wang <ruifeng.w...@arm.com>
> Reviewed-by: Nathan Brown <nathan.br...@arm.com>
This patch does too many things at the same time.
There is code movement and behavior modifications all mixed in.
As there was still no review from the lib maintainer... I am going a
bit more in depth this time.
Please split this patch to make it less hard to understand.
I can see the need for at least one patch for isolating the change on
sig_cmp_fn from the exposed API, then one patch for moving the code to
per arch headers with *no behavior change*, and one patch for
introducing/switching to "dense hitmask".
More comments below.
> ---
> .mailmap | 1 +
> lib/hash/compare_signatures_arm_pvt.h | 60 +++++++
> lib/hash/compare_signatures_generic_pvt.h | 37 +++++
> lib/hash/compare_signatures_x86_pvt.h | 49 ++++++
> lib/hash/hash_sig_cmp_func_pvt.h | 20 +++
> lib/hash/rte_cuckoo_hash.c | 190 +++++++++++-----------
> lib/hash/rte_cuckoo_hash.h | 10 +-
> 7 files changed, 267 insertions(+), 100 deletions(-)
> create mode 100644 lib/hash/compare_signatures_arm_pvt.h
> create mode 100644 lib/hash/compare_signatures_generic_pvt.h
> create mode 100644 lib/hash/compare_signatures_x86_pvt.h
> create mode 100644 lib/hash/hash_sig_cmp_func_pvt.h
>
> diff --git a/.mailmap b/.mailmap
> index f76037213d..ec525981fe 100644
> --- a/.mailmap
> +++ b/.mailmap
> @@ -1661,6 +1661,7 @@ Yixue Wang <yixue.w...@intel.com>
> Yi Yang <yangy...@inspur.com> <yi.y.y...@intel.com>
> Yi Zhang <zhang.y...@zte.com.cn>
> Yoann Desmouceaux <ydesm...@cisco.com>
> +Yoan Picchi <yoan.pic...@arm.com>
> Yogesh Jangra <yogesh.jan...@intel.com>
> Yogev Chaimovich <yo...@cgstowernetworks.com>
> Yongjie Gu <yongjiex...@intel.com>
> diff --git a/lib/hash/compare_signatures_arm_pvt.h
> b/lib/hash/compare_signatures_arm_pvt.h
> new file mode 100644
> index 0000000000..e83bae9912
> --- /dev/null
> +++ b/lib/hash/compare_signatures_arm_pvt.h
I guess pvt stands for private.
No need for such suffix, this header won't be exported in any case.
> @@ -0,0 +1,60 @@
> +/* 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.
> + */
Please put a header guard.
#ifndef <UPPERCASE_HEADER_NAME>_H
#define <UPPERCASE_HEADER_NAME>_H
> +
> +#include <inttypes.h>
> +#include <rte_common.h>
> +#include <rte_vect.h>
> +
> +#include "rte_cuckoo_hash.h"
> +#include "hash_sig_cmp_func_pvt.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),
> + "hitmask_buffer must be wide enough to fit a dense hitmask");
> +
> + /* 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;
> + }
> + }
> +}
IIRC, this code is copied in all three headers.
It is a common scalar version, so the ARM code could simply call the
"generic" implementation rather than copy/paste.
[snip]
> diff --git a/lib/hash/compare_signatures_x86_pvt.h
> b/lib/hash/compare_signatures_x86_pvt.h
> new file mode 100644
> index 0000000000..932912ba19
> --- /dev/null
> +++ b/lib/hash/compare_signatures_x86_pvt.h
> @@ -0,0 +1,49 @@
> +/* 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"
> +#include "hash_sig_cmp_func_pvt.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
The check on RTE_HASH_BUCKET_ENTRIES <= 8 seems new.
It was not present in the previous implementation for SSE2, and this
difference is not explained.
> + 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);
> + }
> + }
> +}
> diff --git a/lib/hash/hash_sig_cmp_func_pvt.h
> b/lib/hash/hash_sig_cmp_func_pvt.h
> new file mode 100644
> index 0000000000..d8d2fbffaf
> --- /dev/null
> +++ b/lib/hash/hash_sig_cmp_func_pvt.h
Please rename as compare_signatures.h or maybe a simpler option is to
move this enum declaration in rte_cuckoo_hash.c before including the
per arch headers.
> @@ -0,0 +1,20 @@
> +/* SPDX-License-Identifier: BSD-3-Clause
> + * Copyright(c) 2024 Arm Limited
> + */
> +
> +#ifndef _SIG_CMP_FUNC_H_
> +#define _SIG_CMP_FUNC_H_
If keeping a header, this guard must reflect the file name.
> +
> +/** Enum used to select the implementation of the signature comparison
> function to use
/* is enough, doxygen only parses public headers.
> + * eg: A system supporting SVE might want to use a NEON implementation.
> + * Those may change and are for internal use only
> + */
> +enum rte_hash_sig_compare_function {
> + RTE_HASH_COMPARE_SCALAR = 0,
> + RTE_HASH_COMPARE_SSE,
> + RTE_HASH_COMPARE_NEON,
> + RTE_HASH_COMPARE_SVE,
> + RTE_HASH_COMPARE_NUM
> +};
> +
> +#endif
[snip]
> diff --git a/lib/hash/rte_cuckoo_hash.h b/lib/hash/rte_cuckoo_hash.h
> index a528f1d1a0..26a992419a 100644
> --- a/lib/hash/rte_cuckoo_hash.h
> +++ b/lib/hash/rte_cuckoo_hash.h
> @@ -134,14 +134,6 @@ struct rte_hash_key {
> char key[0];
> };
>
> -/* All different signature compare functions */
> -enum rte_hash_sig_compare_function {
> - RTE_HASH_COMPARE_SCALAR = 0,
> - RTE_HASH_COMPARE_SSE,
> - RTE_HASH_COMPARE_NEON,
> - RTE_HASH_COMPARE_NUM
> -};
> -
> /** Bucket structure */
> struct __rte_cache_aligned rte_hash_bucket {
> uint16_t sig_current[RTE_HASH_BUCKET_ENTRIES];
> @@ -199,7 +191,7 @@ struct __rte_cache_aligned rte_hash {
> /**< Custom function used to compare keys. */
> enum cmp_jump_table_case cmp_jump_table_idx;
> /**< Indicates which compare function to use. */
> - enum rte_hash_sig_compare_function sig_cmp_fn;
> + unsigned int sig_cmp_fn;
>From an ABI perspective, it looks ok.
We may be breaking users that would inspect this public object, but I
think it is ok.
In any case, put this change in a separate patch so it is more visible.
> /**< Indicates which signature compare function to use. */
> uint32_t bucket_bitmask;
> /**< Bitmask for getting bucket index from hash signature. */
> --
> 2.25.1
>
--
David Marchand
