Re: [dpdk-dev] [PATCH v3 6/8] net/ice: support Rx AVX2 vector

["Lu, Wenzhuo" <wenzhuo.lu@intel.com>]

Hi Ferruh,


> -----Original Message-----
> From: Yigit, Ferruh
> Sent: Saturday, March 16, 2019 1:54 AM
> To: Lu, Wenzhuo <wenzhuo.lu@intel.com>; dev@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH v3 6/8] net/ice: support Rx AVX2 vector
> 
> On 3/15/2019 6:22 AM, Wenzhuo Lu wrote:
> > Signed-off-by: Wenzhuo Lu <wenzhuo.lu@intel.com>
> <...>
> 
> > +#ifdef RTE_LIBRTE_ICE_16BYTE_RX_DESC
> > +		/* for AVX we need alignment otherwise loads are not
> atomic */
> > +		if (avx_aligned) {
> > +			/* load in descriptors, 2 at a time, in reverse order */
> > +			raw_desc6_7 = _mm256_load_si256((void *)(rxdp +
> 6));
> > +			rte_compiler_barrier();
> > +			raw_desc4_5 = _mm256_load_si256((void *)(rxdp +
> 4));
> > +			rte_compiler_barrier();
> > +			raw_desc2_3 = _mm256_load_si256((void *)(rxdp +
> 2));
> > +			rte_compiler_barrier();
> > +			raw_desc0_1 = _mm256_load_si256((void *)(rxdp +
> 0));
> > +		} else
> > +#endif
> > +		do {
> > +			const __m128i raw_desc7 =
> > +				_mm_load_si128((void *)(rxdp + 7));
> > +			rte_compiler_barrier();
> > +			const __m128i raw_desc6 =
> > +				_mm_load_si128((void *)(rxdp + 6));
> > +			rte_compiler_barrier();
> > +			const __m128i raw_desc5 =
> > +				_mm_load_si128((void *)(rxdp + 5));
> > +			rte_compiler_barrier();
> > +			const __m128i raw_desc4 =
> > +				_mm_load_si128((void *)(rxdp + 4));
> > +			rte_compiler_barrier();
> > +			const __m128i raw_desc3 =
> > +				_mm_load_si128((void *)(rxdp + 3));
> > +			rte_compiler_barrier();
> > +			const __m128i raw_desc2 =
> > +				_mm_load_si128((void *)(rxdp + 2));
> > +			rte_compiler_barrier();
> > +			const __m128i raw_desc1 =
> > +				_mm_load_si128((void *)(rxdp + 1));
> > +			rte_compiler_barrier();
> > +			const __m128i raw_desc0 =
> > +				_mm_load_si128((void *)(rxdp + 0));
> > +
> > +			raw_desc6_7 =
> > +				_mm256_inserti128_si256
> > +
> 	(_mm256_castsi128_si256(raw_desc6),
> > +					 raw_desc7, 1);
> > +			raw_desc4_5 =
> > +				_mm256_inserti128_si256
> > +
> 	(_mm256_castsi128_si256(raw_desc4),
> > +					 raw_desc5, 1);
> > +			raw_desc2_3 =
> > +				_mm256_inserti128_si256
> > +
> 	(_mm256_castsi128_si256(raw_desc2),
> > +					 raw_desc3, 1);
> > +			raw_desc0_1 =
> > +				_mm256_inserti128_si256
> > +
> 	(_mm256_castsi128_si256(raw_desc0),
> > +					 raw_desc1, 1);
> > +		} while (0);
> 
> Is this to provide the proper indention because of the above #ifdef block? If
> so why not simple { } for the scope, is do{ }while(0) has benefit against it?
Yes, it's for the indention. To my opinion, "do while" looks friendly to the readers as we always use it in the macros. Only "{}" looks missing a function name or a "for ()" :)