[dpdk-dev] [PATCH v2 1/2] net/ixgbe: eliminate mbuf write on rearm

[Konstantin Ananyev]

With the mbuf rework, we now have 8 contiguous bytes to be rearmed in the
mbuf just before the 8-bytes of olflags. If we don't do the rearm write
inside the descriptor ring replenishment function, and delay it to
receiving the packet, we can do a single 16B write inside the RX function
to set both the rearm data, and the flags together.

Signed-off-by: Konstantin Ananyev <konstantin.ananyev at intel.com>
---
 drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c | 72 ++++++++++++++++++++++++----------
 1 file changed, 52 insertions(+), 20 deletions(-)

diff --git a/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c b/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c
index 62afe31..8e19b9d 100644
--- a/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c
+++ b/drivers/net/ixgbe/ixgbe_rxtx_vec_sse.c
@@ -82,19 +82,23 @@ ixgbe_rxq_rearm(struct ixgbe_rx_queue *rxq)
 	/* Initialize the mbufs in vector, process 2 mbufs in one loop */
 	for (i = 0; i < RTE_IXGBE_RXQ_REARM_THRESH; i += 2, rxep += 2) {
 		__m128i vaddr0, vaddr1;
-		uintptr_t p0, p1;
 
 		mb0 = rxep[0].mbuf;
 		mb1 = rxep[1].mbuf;
 
-		/*
-		 * Flush mbuf with pkt template.
-		 * Data to be rearmed is 6 bytes long.
-		 */
-		p0 = (uintptr_t)&mb0->rearm_data;
-		*(uint64_t *)p0 = rxq->mbuf_initializer;
-		p1 = (uintptr_t)&mb1->rearm_data;
-		*(uint64_t *)p1 = rxq->mbuf_initializer;
+#ifndef RTE_IXGBE_RX_OLFLAGS_ENABLE
+		{
+			uintptr_t p0, p1;
+			/*
+			 * Flush mbuf with pkt template.
+			 * Data to be rearmed is 6 bytes long.
+			 */
+			p0 = (uintptr_t)&mb0->rearm_data;
+			*(uint64_t *)p0 = rxq->mbuf_initializer;
+			p1 = (uintptr_t)&mb1->rearm_data;
+			*(uint64_t *)p1 = rxq->mbuf_initializer;
+		}
+#endif
 
 		/* load buf_addr(lo 64bit) and buf_physaddr(hi 64bit) */
 		vaddr0 = _mm_loadu_si128((__m128i *)&(mb0->buf_addr));
@@ -139,14 +143,11 @@ ixgbe_rxq_rearm(struct ixgbe_rx_queue *rxq)
 #ifdef RTE_IXGBE_RX_OLFLAGS_ENABLE
 
 static inline void
-desc_to_olflags_v(__m128i descs[4], uint8_t vlan_flags,
+desc_to_olflags_v(__m128i descs[4], __m128i mbuf_init, uint8_t vlan_flags,
 	struct rte_mbuf **rx_pkts)
 {
 	__m128i ptype0, ptype1, vtag0, vtag1, csum;
-	union {
-		uint16_t e[4];
-		uint64_t dword;
-	} vol;
+	__m128i rearm0, rearm1, rearm2, rearm3;
 
 	/* mask everything except rss type */
 	const __m128i rsstype_msk = _mm_set_epi16(
@@ -225,12 +226,40 @@ desc_to_olflags_v(__m128i descs[4], uint8_t vlan_flags,
 	vtag1 = _mm_or_si128(vtag0, vtag1);
 
 	vtag1 = _mm_or_si128(ptype0, vtag1);
-	vol.dword = _mm_cvtsi128_si64(vtag1);
 
-	rx_pkts[0]->ol_flags = vol.e[0];
-	rx_pkts[1]->ol_flags = vol.e[1];
-	rx_pkts[2]->ol_flags = vol.e[2];
-	rx_pkts[3]->ol_flags = vol.e[3];
+	/*
+	 * At this point, we have the 4 sets of flags in the low 64-bits
+	 * of vtag1 (4x16).
+	 * We want to extract these, and merge them with the mbuf init data
+	 * so we can do a single 16-byte write to the mbuf to set the flags
+	 * and all the other initialization fields. Extracting the
+	 * appropriate flags means that we have to do a shift and blend for
+	 * each mbuf before we do the write.
+	 */
+#ifdef RTE_MACHINE_CPUFLAG_SSE4_2
+
+	rearm0 = _mm_blend_epi16(mbuf_init, _mm_slli_si128(vtag1, 8), 0x10);
+	rearm1 = _mm_blend_epi16(mbuf_init, _mm_slli_si128(vtag1, 6), 0x10);
+	rearm2 = _mm_blend_epi16(mbuf_init, _mm_slli_si128(vtag1, 4), 0x10);
+	rearm3 = _mm_blend_epi16(mbuf_init, _mm_slli_si128(vtag1, 2), 0x10);
+
+#else
+	rearm0 = _mm_slli_si128(vtag1, 14);
+	rearm1 = _mm_slli_si128(vtag1, 12);
+	rearm2 = _mm_slli_si128(vtag1, 10);
+	rearm3 = _mm_slli_si128(vtag1, 8);
+
+	rearm0 = _mm_or_si128(mbuf_init, _mm_srli_epi64(rearm0, 48));
+	rearm1 = _mm_or_si128(mbuf_init, _mm_srli_epi64(rearm1, 48));
+	rearm2 = _mm_or_si128(mbuf_init, _mm_srli_epi64(rearm2, 48));
+	rearm3 = _mm_or_si128(mbuf_init, _mm_srli_epi64(rearm3, 48));
+
+#endif /* RTE_MACHINE_CPUFLAG_SSE4_2 */
+
+	_mm_store_si128((__m128i *)&rx_pkts[0]->rearm_data, rearm0);
+	_mm_store_si128((__m128i *)&rx_pkts[1]->rearm_data, rearm1);
+	_mm_store_si128((__m128i *)&rx_pkts[2]->rearm_data, rearm2);
+	_mm_store_si128((__m128i *)&rx_pkts[3]->rearm_data, rearm3);
 }
 #else
 #define desc_to_olflags_v(desc, vlan_flags, rx_pkts) do { \
@@ -265,6 +294,7 @@ _recv_raw_pkts_vec(struct ixgbe_rx_queue *rxq, struct rte_mbuf **rx_pkts,
 				0, 0            /* ignore pkt_type field */
 			);
 	__m128i dd_check, eop_check;
+	__m128i mbuf_init;
 	uint8_t vlan_flags;
 
 	/* nb_pkts shall be less equal than RTE_IXGBE_MAX_RX_BURST */
@@ -310,6 +340,8 @@ _recv_raw_pkts_vec(struct ixgbe_rx_queue *rxq, struct rte_mbuf **rx_pkts,
 		0xFF, 0xFF
 		);
 
+	mbuf_init = _mm_set_epi64x(0, rxq->mbuf_initializer);
+
 	/* Cache is empty -> need to scan the buffer rings, but first move
 	 * the next 'n' mbufs into the cache
 	 */
@@ -382,7 +414,7 @@ _recv_raw_pkts_vec(struct ixgbe_rx_queue *rxq, struct rte_mbuf **rx_pkts,
 		sterr_tmp1 = _mm_unpackhi_epi32(descs[1], descs[0]);
 
 		/* set ol_flags with vlan packet type */
-		desc_to_olflags_v(descs, vlan_flags, &rx_pkts[pos]);
+		desc_to_olflags_v(descs, mbuf_init, vlan_flags, &rx_pkts[pos]);
 
 		/* D.2 pkt 3,4 set in_port/nb_seg and remove crc */
 		pkt_mb4 = _mm_add_epi16(pkt_mb4, crc_adjust);
-- 
2.5.0