net: limit each hash list length to MAX_GRO_SKBS

After commit 07d78363dcff ("net: Convert NAPI gro list into a small hash
table.")' there is 8 hash buckets, which allows more flows to be held for
merging.  but MAX_GRO_SKBS, the total held skb for merging, is 8 skb still,
limit the hash table performance.

keep MAX_GRO_SKBS as 8 skb, but limit each hash list length to 8 skb, not
the total 8 skb

Signed-off-by: Li RongQing <lirongqing@baidu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 23 insertions, 33 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 7e6a2f66db5c..89825c1eccdc 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -149,7 +149,6 @@
 
 #include "net-sysfs.h"
 
-/* Instead of increasing this, you should create a hash table. */
 #define MAX_GRO_SKBS 8
 
 /* This should be increased if a protocol with a bigger head is added. */
@@ -5151,9 +5150,10 @@ out:
         return netif_receive_skb_internal(skb);
 }
 
-static void __napi_gro_flush_chain(struct napi_struct *napi, struct list_head *head,
+static void __napi_gro_flush_chain(struct napi_struct *napi, u32 index,
                                    bool flush_old)
 {
+        struct list_head *head = &napi->gro_hash[index].list;
         struct sk_buff *skb, *p;
 
         list_for_each_entry_safe_reverse(skb, p, head, list) {
@@ -5162,22 +5162,20 @@ static void __napi_gro_flush_chain(struct napi_struct *napi, struct list_head *h
                 list_del_init(&skb->list);
                 napi_gro_complete(skb);
                 napi->gro_count--;
+                napi->gro_hash[index].count--;
         }
 }
 
-/* napi->gro_hash contains packets ordered by age.
+/* napi->gro_hash[].list contains packets ordered by age.
  * youngest packets at the head of it.
  * Complete skbs in reverse order to reduce latencies.
  */
 void napi_gro_flush(struct napi_struct *napi, bool flush_old)
 {
-        int i;
-
-        for (i = 0; i < GRO_HASH_BUCKETS; i++) {
-                struct list_head *head = &napi->gro_hash[i];
+        u32 i;
 
-                __napi_gro_flush_chain(napi, head, flush_old);
-        }
+        for (i = 0; i < GRO_HASH_BUCKETS; i++)
+                __napi_gro_flush_chain(napi, i, flush_old);
 }
 EXPORT_SYMBOL(napi_gro_flush);
 
@@ -5189,7 +5187,7 @@ static struct list_head *gro_list_prepare(struct napi_struct *napi,
         struct list_head *head;
         struct sk_buff *p;
 
-        head = &napi->gro_hash[hash & (GRO_HASH_BUCKETS - 1)];
+        head = &napi->gro_hash[hash & (GRO_HASH_BUCKETS - 1)].list;
         list_for_each_entry(p, head, list) {
                 unsigned long diffs;
 
@@ -5257,27 +5255,13 @@ static void gro_pull_from_frag0(struct sk_buff *skb, int grow)
         }
 }
 
-static void gro_flush_oldest(struct napi_struct *napi)
+static void gro_flush_oldest(struct list_head *head)
 {
-        struct sk_buff *oldest = NULL;
-        unsigned long age = jiffies;
-        int i;
-
-        for (i = 0; i < GRO_HASH_BUCKETS; i++) {
-                struct list_head *head = &napi->gro_hash[i];
-                struct sk_buff *skb;
-
-                if (list_empty(head))
-                        continue;
+        struct sk_buff *oldest;
 
-                skb = list_last_entry(head, struct sk_buff, list);
-                if (!oldest || time_before(NAPI_GRO_CB(skb)->age, age)) {
-                        oldest = skb;
-                        age = NAPI_GRO_CB(skb)->age;
-                }
-        }
+        oldest = list_last_entry(head, struct sk_buff, list);
 
-        /* We are called with napi->gro_count >= MAX_GRO_SKBS, so this is
+        /* We are called with head length >= MAX_GRO_SKBS, so this is
          * impossible.
          */
         if (WARN_ON_ONCE(!oldest))
@@ -5292,6 +5276,7 @@ static void gro_flush_oldest(struct napi_struct *napi)
 
 static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff *skb)
 {
+        u32 hash = skb_get_hash_raw(skb) & (GRO_HASH_BUCKETS - 1);
         struct list_head *head = &offload_base;
         struct packet_offload *ptype;
         __be16 type = skb->protocol;
@@ -5358,6 +5343,7 @@ static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff
                 list_del_init(&pp->list);
                 napi_gro_complete(pp);
                 napi->gro_count--;
+                napi->gro_hash[hash].count--;
         }
 
         if (same_flow)
@@ -5366,10 +5352,11 @@ 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_count >= MAX_GRO_SKBS)) {
-                gro_flush_oldest(napi);
+        if (unlikely(napi->gro_hash[hash].count >= MAX_GRO_SKBS)) {
+                gro_flush_oldest(gro_head);
         } else {
                 napi->gro_count++;
+                napi->gro_hash[hash].count++;
         }
         NAPI_GRO_CB(skb)->count = 1;
         NAPI_GRO_CB(skb)->age = jiffies;
@@ -6006,8 +5993,10 @@ void netif_napi_add(struct net_device *dev, struct napi_struct *napi,
         hrtimer_init(&napi->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_PINNED);
         napi->timer.function = napi_watchdog;
         napi->gro_count = 0;
-        for (i = 0; i < GRO_HASH_BUCKETS; i++)
-                INIT_LIST_HEAD(&napi->gro_hash[i]);
+        for (i = 0; i < GRO_HASH_BUCKETS; i++) {
+                INIT_LIST_HEAD(&napi->gro_hash[i].list);
+                napi->gro_hash[i].count = 0;
+        }
         napi->skb = NULL;
         napi->poll = poll;
         if (weight > NAPI_POLL_WEIGHT)
@@ -6047,8 +6036,9 @@ static void flush_gro_hash(struct napi_struct *napi)
         for (i = 0; i < GRO_HASH_BUCKETS; i++) {
                 struct sk_buff *skb, *n;
 
-                list_for_each_entry_safe(skb, n, &napi->gro_hash[i], list)
+                list_for_each_entry_safe(skb, n, &napi->gro_hash[i].list, list)
                         kfree_skb(skb);
+                napi->gro_hash[i].count = 0;
         }
 }