[PATCH net-next 2/4] gro: don't dereference napi->gro_hash[x] multiple times in dev_gro_receive()

[Alexander Lobakin]

GRO bucket index doesn't change through the entire function.
Store a pointer to the corresponding bucket on stack once and use
it later instead of dereferencing again and again.

Signed-off-by: Alexander Lobakin <aloba...@pm.me>
---
 net/core/dev.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index adc42ba7ffd8..ee124aecb8a2 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5957,6 +5957,7 @@ static void gro_flush_oldest(struct napi_struct *napi, 
struct list_head *head)
 static enum gro_result dev_gro_receive(struct napi_struct *napi, struct 
sk_buff *skb)
 {
        u32 bucket = skb_get_hash_raw(skb) & (GRO_HASH_BUCKETS - 1);
+       struct gro_list *gro_list = &napi->gro_hash[bucket];
        struct list_head *head = &offload_base;
        struct packet_offload *ptype;
        __be16 type = skb->protocol;
@@ -6024,7 +6025,7 @@ static enum gro_result dev_gro_receive(struct napi_struct 
*napi, struct sk_buff
        if (pp) {
                skb_list_del_init(pp);
                napi_gro_complete(napi, pp);
-               napi->gro_hash[bucket].count--;
+               gro_list->count--;
        }

        if (same_flow)
@@ -6033,10 +6034,10 @@ static enum gro_result dev_gro_receive(struct 
napi_struct *napi, struct sk_buff
        if (NAPI_GRO_CB(skb)->flush)
                goto normal;

-       if (unlikely(napi->gro_hash[bucket].count >= MAX_GRO_SKBS)) {
+       if (unlikely(gro_list->count >= MAX_GRO_SKBS)) {
                gro_flush_oldest(napi, gro_head);
        } else {
-               napi->gro_hash[bucket].count++;
+               gro_list->count++;
        }
        NAPI_GRO_CB(skb)->count = 1;
        NAPI_GRO_CB(skb)->age = jiffies;
@@ -6050,7 +6051,7 @@ static enum gro_result dev_gro_receive(struct napi_struct 
*napi, struct sk_buff
        if (grow > 0)
                gro_pull_from_frag0(skb, grow);
 ok:
-       if (napi->gro_hash[bucket].count) {
+       if (gro_list->count) {
                if (!test_bit(bucket, &napi->gro_bitmask))
                        __set_bit(bucket, &napi->gro_bitmask);
        } else if (test_bit(bucket, &napi->gro_bitmask)) {
--
2.30.2