[PATCH] app/testpmd: improve sse based macswap

[Vipin Varghese <vipin.varghese@amd.com>]

Goal of the patch is to improve SSE macswap on x86_64 by reducing
the stalls in backend engine. Original implementation of the SSE
macswap makes loop call to multiple load, shuffle & store. Using
SIMD ISA interleaving we can reduce the stalls for
 - load SSE token exhaustion
 - Shuffle and Load dependency

Also other changes which improves packet per second are
 - Filling access to MBUF for offload flags which is separate cacheline,
 - using register keyword

Build test using meson script:
``````````````````````````````

build-gcc-static
buildtools
build-gcc-shared
build-mini
build-clang-static
build-clang-shared
build-x86-generic

Test Results:
`````````````

Platform-1: AMD EPYC SIENA 8594P @2.3GHz, no boost

------------------------------------------------
TEST IO 64B: baseline <NIC : MPPs>
 - mellanox CX-7 2*200Gbps : 42.0
 - intel E810 1*100Gbps : 82.0
 - intel E810 2*200Gbps (2CQ-DA2): 82.45
------------------------------------------------
TEST MACSWAP 64B: <NIC : Before : After>
 - mellanox CX-7 2*200Gbps : 31.533 : 31.90
 - intel E810 1*100Gbps : 50.380 : 47.0
 - intel E810 2*200Gbps (2CQ-DA2): 48.840 : 49.827
------------------------------------------------
TEST MACSWAP 128B: <NIC : Before: After>
 - mellanox CX-7 2*200Gbps: 30.946 : 31.770
 - intel E810 1*100Gbps: 49.386 : 46.366
 - intel E810 2*200Gbps (2CQ-DA2): 47.979 : 49.503
------------------------------------------------
TEST MACSWAP 256B: <NIC: Before: After>
 - mellanox CX-7 2*200Gbps: 32.480 : 33.150
 - intel E810 1 * 100Gbps: 45.29 : 44.571
 - intel E810 2 * 200Gbps (2CQ-DA2): 45.033 : 45.117
------------------------------------------------

Platform-2: AMD EPYC 9554 @3.1GHz, no boost

------------------------------------------------
TEST IO 64B: baseline <NIC : MPPs>
 - intel E810 2*200Gbps (2CQ-DA2): 82.49
------------------------------------------------
<NIC intel E810 2*200Gbps (2CQ-DA2): Before : After>
TEST MACSWAP: 1Q 1C1T
 64B: : 45.0 : 45.54
128B: : 44.48 : 44.43
256B: : 42.0 : 41.99
+++++++++++++++++++++++++
TEST MACSWAP: 2Q 2C2T
 64B: : 59.5 : 60.55
128B: : 56.78 : 58.1
256B: : 41.85 : 41.99
------------------------------------------------

Signed-off-by: Vipin Varghese <vipin.varghese@amd.com>
---
 app/test-pmd/macswap_sse.h | 37 +++++++++++++++++--------------------
 1 file changed, 17 insertions(+), 20 deletions(-)

diff --git a/app/test-pmd/macswap_sse.h b/app/test-pmd/macswap_sse.h
index 223f87a539..6e4ed21924 100644
--- a/app/test-pmd/macswap_sse.h
+++ b/app/test-pmd/macswap_sse.h
@@ -16,16 +16,16 @@ do_macswap(struct rte_mbuf *pkts[], uint16_t nb,
 	uint64_t ol_flags;
 	int i;
 	int r;
-	__m128i addr0, addr1, addr2, addr3;
+	register __m128i addr0, addr1, addr2, addr3;
 	/**
 	 * shuffle mask be used to shuffle the 16 bytes.
 	 * byte 0-5 wills be swapped with byte 6-11.
 	 * byte 12-15 will keep unchanged.
 	 */
-	__m128i shfl_msk = _mm_set_epi8(15, 14, 13, 12,
-					5, 4, 3, 2,
-					1, 0, 11, 10,
-					9, 8, 7, 6);
+	register const __m128i shfl_msk = _mm_set_epi8(15, 14, 13, 12,
+							5, 4, 3, 2,
+							1, 0, 11, 10,
+							9, 8, 7, 6);
 
 	ol_flags = ol_flags_init(txp->dev_conf.txmode.offloads);
 	vlan_qinq_set(pkts, nb, ol_flags,
@@ -44,23 +44,24 @@ do_macswap(struct rte_mbuf *pkts[], uint16_t nb,
 
 		mb[0] = pkts[i++];
 		eth_hdr[0] = rte_pktmbuf_mtod(mb[0], struct rte_ether_hdr *);
-		addr0 = _mm_loadu_si128((__m128i *)eth_hdr[0]);
-
 		mb[1] = pkts[i++];
 		eth_hdr[1] = rte_pktmbuf_mtod(mb[1], struct rte_ether_hdr *);
-		addr1 = _mm_loadu_si128((__m128i *)eth_hdr[1]);
-
-
 		mb[2] = pkts[i++];
 		eth_hdr[2] = rte_pktmbuf_mtod(mb[2], struct rte_ether_hdr *);
-		addr2 = _mm_loadu_si128((__m128i *)eth_hdr[2]);
-
 		mb[3] = pkts[i++];
 		eth_hdr[3] = rte_pktmbuf_mtod(mb[3], struct rte_ether_hdr *);
-		addr3 = _mm_loadu_si128((__m128i *)eth_hdr[3]);
 
+		/* Interleave loads and shuffle with field set */
+		addr0 = _mm_loadu_si128((__m128i *)eth_hdr[0]);
+		mbuf_field_set(mb[0], ol_flags);
+		addr1 = _mm_loadu_si128((__m128i *)eth_hdr[1]);
+		mbuf_field_set(mb[1], ol_flags);
 		addr0 = _mm_shuffle_epi8(addr0, shfl_msk);
+		addr2 = _mm_loadu_si128((__m128i *)eth_hdr[2]);
+		mbuf_field_set(mb[2], ol_flags);
 		addr1 = _mm_shuffle_epi8(addr1, shfl_msk);
+		addr3 = _mm_loadu_si128((__m128i *)eth_hdr[3]);
+		mbuf_field_set(mb[3], ol_flags);
 		addr2 = _mm_shuffle_epi8(addr2, shfl_msk);
 		addr3 = _mm_shuffle_epi8(addr3, shfl_msk);
 
@@ -69,25 +70,21 @@ do_macswap(struct rte_mbuf *pkts[], uint16_t nb,
 		_mm_storeu_si128((__m128i *)eth_hdr[2], addr2);
 		_mm_storeu_si128((__m128i *)eth_hdr[3], addr3);
 
-		mbuf_field_set(mb[0], ol_flags);
-		mbuf_field_set(mb[1], ol_flags);
-		mbuf_field_set(mb[2], ol_flags);
-		mbuf_field_set(mb[3], ol_flags);
 		r -= 4;
 	}
 
 	for ( ; i < nb; i++) {
-		if (i < nb - 1)
+		if (i < (nb - 1))
 			rte_prefetch0(rte_pktmbuf_mtod(pkts[i+1], void *));
 		mb[0] = pkts[i];
 		eth_hdr[0] = rte_pktmbuf_mtod(mb[0], struct rte_ether_hdr *);
 
 		/* Swap dest and src mac addresses. */
 		addr0 = _mm_loadu_si128((__m128i *)eth_hdr[0]);
+		/* invoke field_set as it is on separate cacheline */
+		mbuf_field_set(mb[0], ol_flags);
 		addr0 = _mm_shuffle_epi8(addr0, shfl_msk);
 		_mm_storeu_si128((__m128i *)eth_hdr[0], addr0);
-
-		mbuf_field_set(mb[0], ol_flags);
 	}
 }
 
-- 
2.34.1