[PATCH v5 net-next 2/2] net: Cache hash and flow_id to avoid recalculation

[Krishna Kumar <krikku@gmail.com>]

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>
---
 net/core/dev.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 979dcdfdee1f..2c3981b823c7 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4861,7 +4861,8 @@ 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;
@@ -4872,8 +4873,6 @@ 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? */
@@ -4889,9 +4888,6 @@ 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);
 
@@ -4965,6 +4961,7 @@ 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;
 
@@ -5011,7 +5008,8 @@ 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;
 
 		/*
@@ -5030,7 +5028,8 @@ 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)) {
-- 
2.43.0