Re: [dpdk-stable] [PATCH] app/testpmd: improve MAC swap performance

["Wiles, Keith" <keith.wiles@intel.com>]

> On Nov 19, 2018, at 10:45 PM, Zhang, Qi Z <qi.z.zhang@intel.com> wrote:
> 
> The patch optimizes the mac swap operation by taking advantage
> of SSE instructions, it only impacts x86 platform.
> 
> Cc: stable@dpdk.org
> 
> Signed-off-by: Qi Zhang <qi.z.zhang@intel.com>
> ---
> app/test-pmd/macswap.c | 16 +++++++++++++++-
> 1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/app/test-pmd/macswap.c b/app/test-pmd/macswap.c
> index a8384d5b8..0722782b0 100644
> --- a/app/test-pmd/macswap.c
> +++ b/app/test-pmd/macswap.c
> @@ -78,7 +78,6 @@ pkt_burst_mac_swap(struct fwd_stream *fs)
> 	struct rte_port  *txp;
> 	struct rte_mbuf  *mb;
> 	struct ether_hdr *eth_hdr;
> -	struct ether_addr addr;
> 	uint16_t nb_rx;
> 	uint16_t nb_tx;
> 	uint16_t i;
> @@ -95,6 +94,15 @@ pkt_burst_mac_swap(struct fwd_stream *fs)
> 	start_tsc = rte_rdtsc();
> #endif
> 
> +#ifdef RTE_ARCH_X86
> +	__m128i addr;
> +	__m128i shfl_msk = _mm_set_epi8(15, 14, 13, 12,
> +					5, 4, 3, 2,
> +					1, 0, 11, 10,
> +					9, 8, 7, 6);

I was playing around with these mask values and I was not able to make it work as I expected.
I ended up with different values in the mask.

_mm_set_epi8(15, 14, 13, 12, 5, 4, 3, 2, 1, 0, 11, 10, 9, 8, 7, 6);

After dumping the memory for a large number of tests this one seems correct, can you verify your mask is correct?

> +#else
> +	struct ether_addr addr;
> +#endif
> 	/*
> 	 * Receive a burst of packets and forward them.
> 	 */
> @@ -123,9 +131,15 @@ pkt_burst_mac_swap(struct fwd_stream *fs)
> 		eth_hdr = rte_pktmbuf_mtod(mb, struct ether_hdr *);
> 
> 		/* Swap dest and src mac addresses. */
> +#ifdef RTE_ARCH_X86
> +		addr = _mm_loadu_si128((__m128i *)eth_hdr);
> +		addr = _mm_shuffle_epi8(addr, shfl_msk);
> +		_mm_storeu_si128((__m128i *)eth_hdr, addr);
> +#else
> 		ether_addr_copy(&eth_hdr->d_addr, &addr);
> 		ether_addr_copy(&eth_hdr->s_addr, &eth_hdr->d_addr);
> 		ether_addr_copy(&addr, &eth_hdr->s_addr);
> +#endif
> 
> 		mb->ol_flags &= IND_ATTACHED_MBUF | EXT_ATTACHED_MBUF;
> 		mb->ol_flags |= ol_flags;
> -- 
> 2.13.6
> 

Regards,
Keith