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Subject: Re: [PATCH v6 4/4] hash: add SVE support for bulk key lookup
To: Yoan Picchi <yoan.picchi@arm.com>, Yipeng Wang <yipeng1.wang@intel.com>,
Sameh Gobriel <sameh.gobriel@intel.com>, Bruce Richardson
<bruce.richardson@intel.com>, Vladimir Medvedkin
<vladimir.medvedkin@intel.com>
CC: <dev@dpdk.org>, <nd@arm.com>, Harjot Singh <harjot.singh@arm.com>, Nathan
Brown <nathan.brown@arm.com>, Ruifeng Wang <ruifeng.wang@arm.com>
References: <20231020165159.1649282-1-yoan.picchi@arm.com>
<20240311232112.736613-1-yoan.picchi@arm.com>
<20240311232112.736613-5-yoan.picchi@arm.com>
From: fengchengwen <fengchengwen@huawei.com>
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Date: Tue, 12 Mar 2024 11:57:35 +0800
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Hi Yoan,
On 2024/3/12 7:21, Yoan Picchi wrote:
> - Implemented SVE code for comparing signatures in bulk lookup.
> - Added Defines in code for SVE code support.
> - Optimise NEON code
This commit does not include this part. Pls only describe the content in this commit.
> - New SVE code is ~5% slower than optimized NEON for N2 processor.
>
> Signed-off-by: Yoan Picchi <yoan.picchi@arm.com>
> Signed-off-by: Harjot Singh <harjot.singh@arm.com>
> Reviewed-by: Nathan Brown <nathan.brown@arm.com>
> Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> ---
> lib/hash/arch/arm/compare_signatures.h | 58 ++++++++++++++++++++++++++
> lib/hash/rte_cuckoo_hash.c | 2 +
> 2 files changed, 60 insertions(+)
>
> diff --git a/lib/hash/arch/arm/compare_signatures.h b/lib/hash/arch/arm/compare_signatures.h
> index b5a457f936..8a0627e119 100644
> --- a/lib/hash/arch/arm/compare_signatures.h
> +++ b/lib/hash/arch/arm/compare_signatures.h
> @@ -47,6 +47,64 @@ compare_signatures_dense(uint16_t *hitmask_buffer,
> *hitmask_buffer = vaddvq_u16(hit2);
> }
> break;
> +#endif
> +#if defined(RTE_HAS_SVE_ACLE)
> + case RTE_HASH_COMPARE_SVE: {
...
> #endif
> default:
> for (unsigned int i = 0; i < RTE_HASH_BUCKET_ENTRIES; i++) {
> diff --git a/lib/hash/rte_cuckoo_hash.c b/lib/hash/rte_cuckoo_hash.c
> index e41f03270a..7a474267f0 100644
> --- a/lib/hash/rte_cuckoo_hash.c
> +++ b/lib/hash/rte_cuckoo_hash.c
> @@ -452,6 +452,8 @@ rte_hash_create(const struct rte_hash_parameters *params)
> #elif defined(RTE_ARCH_ARM64)
> if (rte_cpu_get_flag_enabled(RTE_CPUFLAG_NEON)) {
> h->sig_cmp_fn = RTE_HASH_COMPARE_NEON;
> + if (rte_cpu_get_flag_enabled(RTE_CPUFLAG_SVE))
> + h->sig_cmp_fn = RTE_HASH_COMPARE_SVE;
The RTE_HASH_COMPARE_SVE was defined in "PATCH v6 1/4] hash: pack the hitmask for hash in bulk lookup",
but its first use is in this commit, so I think it should defined in this commit.
If RTE_CPUFLAG_SVE and RTE_HAS_SVE_ACLE both set, then SVE impl will be chosen.
If RTE_CPUFLAG_SVE defined, but RTE_HAS_SVE_ACLE was not, then scalar will be chosen. --- in this case we could back to NEON impl.
So I suggest direct use "#if defined(RTE_HAS_SVE_ACLE)" here.
> }
> else
> #endif
>
Plus:
I notice the commit log said the SVE performance is slower than NEON.
And I also notice other platform SVE also lower than NEON,
1. b4ee9c07bd config/arm: disable SVE ACLE for CN10K
2. 4eea7c6461 config/arm: add SVE ACLE control flag
So maybe we should disable RTE_HAS_SVE_ACLE default by:
diff --git a/config/arm/meson.build b/config/arm/meson.build
index 9d6fb87d7f..a5b890d100 100644
--- a/config/arm/meson.build
+++ b/config/arm/meson.build
@@ -875,7 +875,7 @@ endif
if cc.get_define('__ARM_FEATURE_SVE', args: machine_args) != ''
compile_time_cpuflags += ['RTE_CPUFLAG_SVE']
- if (cc.check_header('arm_sve.h') and soc_config.get('sve_acle', true))
+ if (cc.check_header('arm_sve.h') and soc_config.get('sve_acle', false))
dpdk_conf.set('RTE_HAS_SVE_ACLE', 1)
endif
endif
If the platform verify SVE has higher performance, then it could enable SVE by add "sve_acle: true" in soc_xxx config.
Thanks