CT: Perf optimization through prefetch and condition checks in CT

JIRA: SAMPLEVNF-10

LLC miss is possible when the connection data structure is accessed
after retrieved from hash table entries for TCP/UDP connection.
CPI for rte_ct_udp_packet() is not good due to if/else condition checks.
This patch provide a prefetch instructions to pre-fetch the cnxn data entry
structure to avoid the LLC miss and also optimize the if/else condition check
to improve the CPI for rte_ct_udp_packet() function.

Change-Id: Ieaf70815c919ddbe1ff34921222eac030fb41756
Signed-off-by: Anand B Jyoti <anand.b.jyoti@intel.com>

2 files changed, 43 insertions, 12 deletions

diff --git a/common/VIL/conntrack/rte_cnxn_tracking.c b/common/VIL/conntrack/rte_cnxn_tracking.c
index 461ed422..aa18058e 100644
--- a/common/VIL/conntrack/rte_cnxn_tracking.c
+++ b/common/VIL/conntrack/rte_cnxn_tracking.c
@@ -52,7 +52,6 @@
 
 #define IP_VERSION_4 4
 #define IP_VERSION_6 6
-
 static void
 rte_ct_cnxn_tracker_batch_lookup_basic_type(
 	struct rte_ct_cnxn_tracker *ct,
@@ -1479,6 +1478,9 @@ rte_ct_cnxn_tracker_batch_lookup_basic_type(
 	int32_t positions[RTE_HASH_LOOKUP_BULK_MAX];
 	uint32_t i;
 	struct rte_ct_cnxn_data new_cnxn_data;
+	struct rte_ct_cnxn_data *cnxn_data_entry[RTE_HASH_LOOKUP_BULK_MAX];
+
+	rte_prefetch0(ct->hash_table_entries);
 
 	if (CNXN_TRX_DEBUG > 1) {
 		printf("Enter cnxn tracker %p", ct);
@@ -1631,6 +1633,35 @@ rte_ct_cnxn_tracker_batch_lookup_basic_type(
 		*pkts_mask = 0;
 		return;	/* unknown error, just discard all packets */
 	}
+
+	/* Pre-fetch hash table entries and counters to avoid LLC miss */
+	rte_prefetch0(ct->counters);
+	for (i = 0; i < packets_for_lookup; i++) {
+		struct rte_ct_cnxn_data *entry = NULL;
+		int hash_table_entry = positions[i];
+
+		if (hash_table_entry >= 0) {
+			/* Entry found for existing UDP/TCP connection */
+			entry = &ct->hash_table_entries[hash_table_entry];
+			rte_prefetch0(&entry->counters.packets_forwarded);
+			rte_prefetch0(entry);
+			rte_prefetch0(&entry->key_is_client_order);
+		}
+		else {
+			uint8_t pkt_index = compacting_map[i];
+			uint32_t *key = ct->hash_key_ptrs[pkt_index];
+			uint8_t protocol = *(key + 9);
+			if (protocol == UDP_PROTOCOL) {
+				/* Search in new connections only for UDP */
+				entry = rte_ct_search_new_connections(ct, key);
+				rte_prefetch0(&entry->counters.packets_forwarded);
+				rte_prefetch0(entry);
+				rte_prefetch0(&entry->key_is_client_order);
+			}
+		}
+		cnxn_data_entry[i] = entry;
+	}
+
 	for (i = 0; i < packets_for_lookup; i++) {
 		/* index into hash table entries */
 		int hash_table_entry = positions[i];
@@ -1689,7 +1720,7 @@ rte_ct_cnxn_tracker_batch_lookup_basic_type(
 				 */
 
 				struct rte_ct_cnxn_data *entry =
-				&ct->hash_table_entries[hash_table_entry];
+					cnxn_data_entry[i];
 
 				if (rte_ct_udp_packet
 						(ct, entry, pkts[pkt_index],
@@ -1704,7 +1735,7 @@ rte_ct_cnxn_tracker_batch_lookup_basic_type(
 				 */
 
 				struct rte_ct_cnxn_data *recent_entry =
-					rte_ct_search_new_connections(ct, key);
+					cnxn_data_entry[i];
 
 				if (recent_entry != NULL) {
 					if (rte_ct_udp_packet(ct, recent_entry,
diff --git a/common/VIL/conntrack/rte_ct_udp.c b/common/VIL/conntrack/rte_ct_udp.c
index 88f3a9a4..6caa788f 100644
--- a/common/VIL/conntrack/rte_ct_udp.c
+++ b/common/VIL/conntrack/rte_ct_udp.c
@@ -33,17 +33,17 @@ enum rte_ct_packet_action rte_ct_udp_packet(struct rte_ct_cnxn_tracker *ct,
 		uint8_t  key_was_flipped)
 {
 	enum rte_ct_pkt_direction dir;
-
+	enum rte_ct_udp_states ustate = RTE_CT_UDP_UNREPLIED;
 	dir = (cd->key_is_client_order == !key_was_flipped);
 	/* printf("packet received verify"); */
-	if (dir == RTE_CT_DIR_REPLY &&
-			cd->connstatus == RTE_INIT_CONN) {
-		rte_ct_set_cnxn_timer_for_udp(ct, cd, RTE_CT_UDP_REPLIED);
+	if (dir == RTE_CT_DIR_REPLY && (
+			(cd->connstatus == RTE_INIT_CONN) ||
+			(cd->connstatus == RTE_ASSURED_CONN)))
+	{
+		ustate = RTE_CT_UDP_REPLIED;
 		cd->connstatus = RTE_ASSURED_CONN;
-	} else if (dir == RTE_CT_DIR_REPLY &&
-			cd->connstatus == RTE_ASSURED_CONN)
-		rte_ct_set_cnxn_timer_for_udp(ct, cd, RTE_CT_UDP_REPLIED);
-	else
-		rte_ct_set_cnxn_timer_for_udp(ct, cd, RTE_CT_UDP_UNREPLIED);
+	}
+	rte_ct_set_cnxn_timer_for_udp(ct, cd, ustate);
+
 	return RTE_CT_FORWARD_PACKET;
 }