[dpdk-dev] [PATCH v4 3/3] efd: run-time dispatch over x86 EFD functions

[Ananyev, Konstantin]

> -----Original Message-----
> From: Li, Xiaoyun
> Sent: Monday, October 2, 2017 5:13 PM
> To: Ananyev, Konstantin <konstantin.ananyev at intel.com>; Richardson, Bruce <bruce.richardson at intel.com>
> Cc: Lu, Wenzhuo <wenzhuo.lu at intel.com>; Zhang, Helin <helin.zhang at intel.com>; dev at dpdk.org; Li, Xiaoyun <xiaoyun.li at intel.com>
> Subject: [PATCH v4 3/3] efd: run-time dispatch over x86 EFD functions
> 
> This patch dynamically selects x86 EFD functions at run-time.
> This patch uses function pointer and binds it to the relative
> function based on CPU flags at constructor time.
> 
> Signed-off-by: Xiaoyun Li <xiaoyun.li at intel.com>
> ---
>  lib/librte_efd/rte_efd_x86.h | 41 ++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 38 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/librte_efd/rte_efd_x86.h b/lib/librte_efd/rte_efd_x86.h
> index 34f37d7..93b6743 100644
> --- a/lib/librte_efd/rte_efd_x86.h
> +++ b/lib/librte_efd/rte_efd_x86.h
> @@ -43,12 +43,29 @@
>  #define EFD_LOAD_SI128(val) _mm_lddqu_si128(val)
>  #endif
> 
> +typedef efd_value_t
> +(*efd_lookup_internal_avx2_t)(const efd_hashfunc_t *group_hash_idx,
> +		const efd_lookuptbl_t *group_lookup_table,
> +		const uint32_t hash_val_a, const uint32_t hash_val_b);
> +
> +static efd_lookup_internal_avx2_t efd_lookup_internal_avx2_ptr;
> +
>  static inline efd_value_t
>  efd_lookup_internal_avx2(const efd_hashfunc_t *group_hash_idx,
>  		const efd_lookuptbl_t *group_lookup_table,
>  		const uint32_t hash_val_a, const uint32_t hash_val_b)
>  {
> -#ifdef RTE_MACHINE_CPUFLAG_AVX2
> +	return (*efd_lookup_internal_avx2_ptr)(group_hash_idx,
> +					       group_lookup_table,
> +					       hash_val_a, hash_val_b);

I don't think you need all that.
All you need - build proper avx2 function even if current HW doesn't support it.
The existing runtime selection here seems ok already.
Konstantin

> +}
> +
> +#ifdef CC_SUPPORT_AVX2
> +static inline efd_value_t
> +efd_lookup_internal_avx2_AVX2(const efd_hashfunc_t *group_hash_idx,
> +		const efd_lookuptbl_t *group_lookup_table,
> +		const uint32_t hash_val_a, const uint32_t hash_val_b)
> +{
>  	efd_value_t value = 0;
>  	uint32_t i = 0;
>  	__m256i vhash_val_a = _mm256_set1_epi32(hash_val_a);
> @@ -74,13 +91,31 @@ efd_lookup_internal_avx2(const efd_hashfunc_t *group_hash_idx,
>  	}
> 
>  	return value;
> -#else
> +}
> +#endif
> +
> +static inline efd_value_t
> +efd_lookup_internal_avx2_DEFAULT(const efd_hashfunc_t *group_hash_idx,
> +		const efd_lookuptbl_t *group_lookup_table,
> +		const uint32_t hash_val_a, const uint32_t hash_val_b)
> +{
>  	RTE_SET_USED(group_hash_idx);
>  	RTE_SET_USED(group_lookup_table);
>  	RTE_SET_USED(hash_val_a);
>  	RTE_SET_USED(hash_val_b);
>  	/* Return dummy value, only to avoid compilation breakage */
>  	return 0;
> -#endif
> +}
> 
> +static void __attribute__((constructor))
> +rte_efd_x86_init(void)
> +{
> +#ifdef CC_SUPPORT_AVX2
> +	if (rte_cpu_get_flag_enabled(RTE_CPUFLAG_AVX2))
> +		efd_lookup_internal_avx2_ptr = efd_lookup_internal_avx2_AVX2;
> +	else
> +		efd_lookup_internal_avx2_ptr = efd_lookup_internal_avx2_DEFAULT;
> +#else
> +	efd_lookup_internal_avx2_ptr = efd_lookup_internal_avx2_DEFAULT;
> +#endif
>  }
> --
> 2.7.4