Re: [dpdk-dev] [PATCH] net/iavf: fix performance drop

["Zhang, Qi Z" <qi.z.zhang@intel.com>]

> -----Original Message-----
> From: dev <dev-bounces@dpdk.org> On Behalf Of Wenzhuo Lu
> Sent: Monday, April 26, 2021 1:30 PM
> To: dev@dpdk.org
> Cc: Lu, Wenzhuo <wenzhuo.lu@intel.com>
> Subject: [dpdk-dev] [PATCH] net/iavf: fix performance drop
> 
> AVX2 and SSE don't have the offload path.
> Not necessary doing any check. Or the scalar path will be chosen.
> 
> Fixes: eff56a7b9f97 ("net/iavf: add offload path for Rx AVX512")
> 
> Signed-off-by: Wenzhuo Lu <wenzhuo.lu@intel.com>
> ---
>  drivers/net/iavf/iavf_rxtx.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/net/iavf/iavf_rxtx.c b/drivers/net/iavf/iavf_rxtx.c index
> 3f3cf63..0ba19dbf 100644
> --- a/drivers/net/iavf/iavf_rxtx.c
> +++ b/drivers/net/iavf/iavf_rxtx.c
> @@ -2401,13 +2401,11 @@
>  	check_ret = iavf_rx_vec_dev_check(dev);
>  	if (check_ret >= 0 &&
>  	    rte_vect_get_max_simd_bitwidth() >= RTE_VECT_SIMD_128) {
> -		if (check_ret == IAVF_VECTOR_PATH) {
> -			use_sse = true;
> -			if ((rte_cpu_get_flag_enabled(RTE_CPUFLAG_AVX2) == 1 ||
> -			     rte_cpu_get_flag_enabled(RTE_CPUFLAG_AVX512F) == 1)
> &&
> -			    rte_vect_get_max_simd_bitwidth() >=
> RTE_VECT_SIMD_256)
> -				use_avx2 = true;
> -		}
> +		use_sse = true;
> +		if ((rte_cpu_get_flag_enabled(RTE_CPUFLAG_AVX2) == 1 ||
> +		     rte_cpu_get_flag_enabled(RTE_CPUFLAG_AVX512F) == 1) &&
> +		    rte_vect_get_max_simd_bitwidth() >= RTE_VECT_SIMD_256)
> +			use_avx2 = true;


Not sure if the right path will be selected when avx512 is not true, (CC_AVX512_SUPPORT is disable) while check_ret is IAVF_VECTOR_OFFLOAD_PATH?

Currently we have 

if (!use_sse && !use_avx2 && !use_avx512)
	goto normal;

Should we also add below check?

if (!use_avx512 && check_ret == IAVF_VECTOR_OFFLOAD_PATH)
   goto normal;

> 
>  #ifdef CC_AVX512_SUPPORT
>  		if (rte_cpu_get_flag_enabled(RTE_CPUFLAG_AVX512F) == 1 &&
> --
> 1.9.3