net: Cache hash and flow_id to avoid recalculation

get_rps_cpu() can cache flow_id and hash as both are required by
set_rps_cpu() instead of recalculating them twice.

Signed-off-by: Krishna Kumar <krikku@gmail.com>
Signed-off-by: NipaLocal <nipa@local>

Author: krikkku

net/core/dev.c

@@ -4869,7 +4869,8 @@ static bool rps_flow_is_active(struct rps_dev_flow *rflow,
 
 static struct rps_dev_flow *
 set_rps_cpu(struct net_device *dev, struct sk_buff *skb,
-	    struct rps_dev_flow *rflow, u16 next_cpu)
+	    struct rps_dev_flow *rflow, u16 next_cpu, u32 hash,
+	    u32 flow_id)
 {
 	if (next_cpu < nr_cpu_ids) {
 		u32 head;
@@ -4880,8 +4881,6 @@ set_rps_cpu(struct net_device *dev, struct sk_buff *skb,
 		struct rps_dev_flow *tmp_rflow;
 		unsigned int tmp_cpu;
 		u16 rxq_index;
-		u32 flow_id;
-		u32 hash;
 		int rc;
 
 		/* Should we steer this flow to a different hardware queue? */
@@ -4897,9 +4896,6 @@ set_rps_cpu(struct net_device *dev, struct sk_buff *skb,
 		if (!flow_table)
 			goto out;
 
-		hash = skb_get_hash(skb);
-		flow_id = rfs_slot(hash, flow_table);
-
 		tmp_rflow = &flow_table->flows[flow_id];
 		tmp_cpu = READ_ONCE(tmp_rflow->cpu);
 
@@ -4947,6 +4943,7 @@ static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb,
 	struct rps_dev_flow_table *flow_table;
 	struct rps_map *map;
 	int cpu = -1;
+	u32 flow_id;
 	u32 tcpu;
 	u32 hash;
 
@@ -4993,7 +4990,8 @@ static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb,
 		/* OK, now we know there is a match,
 		 * we can look at the local (per receive queue) flow table
 		 */
-		rflow = &flow_table->flows[rfs_slot(hash, flow_table)];
+		flow_id = rfs_slot(hash, flow_table);
+		rflow = &flow_table->flows[flow_id];
 		tcpu = rflow->cpu;
 
 		/*
@@ -5012,7 +5010,8 @@ static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb,
 		     ((int)(READ_ONCE(per_cpu(softnet_data, tcpu).input_queue_head) -
 		      rflow->last_qtail)) >= 0)) {
 			tcpu = next_cpu;
-			rflow = set_rps_cpu(dev, skb, rflow, next_cpu);
+			rflow = set_rps_cpu(dev, skb, rflow, next_cpu, hash,
+					    flow_id);
 		}
 
 		if (tcpu < nr_cpu_ids && cpu_online(tcpu)) {