net: convert gro_count to bitmask

gro_hash size is 192 bytes, and uses 3 cache lines, if there is few
flows, gro_hash may be not fully used, so it is unnecessary to iterate
all gro_hash in napi_gro_flush(), to occupy unnecessary cacheline.

convert gro_count to a bitmask, and rename it as gro_bitmask, each bit
represents a element of gro_hash, only flush a gro_hash element if the
related bit is set, to speed up napi_gro_flush().

and update gro_bitmask only if it will be changed, to reduce cache
update

Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Li RongQing <lirongqing@baidu.com>
Cc: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 3514d67..c1295c7 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -308,9 +308,14 @@ struct gro_list {
 };
 
 /*
- * Structure for NAPI scheduling similar to tasklet but with weighting
+ * size of gro hash buckets, must less than bit number of
+ * napi_struct::gro_bitmask
  */
 #define GRO_HASH_BUCKETS       8
+
+/*
+ * Structure for NAPI scheduling similar to tasklet but with weighting
+ */
 struct napi_struct {
        /* The poll_list must only be managed by the entity which
         * changes the state of the NAPI_STATE_SCHED bit.  This means
@@ -322,7 +327,7 @@ struct napi_struct {
 
        unsigned long           state;
        int                     weight;
-       unsigned int            gro_count;
+       unsigned long           gro_bitmask;
        int                     (*poll)(struct napi_struct *, int);
 #ifdef CONFIG_NETPOLL
        int                     poll_owner;

diff --git a/net/core/dev.c b/net/core/dev.c
index 0df1771..c883b17 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5282,9 +5282,11 @@ static void __napi_gro_flush_chain(struct napi_struct *napi, u32 index,
                list_del(&skb->list);
                skb->next = NULL;
                napi_gro_complete(skb);
-               napi->gro_count--;
                napi->gro_hash[index].count--;
        }
+
+       if (!napi->gro_hash[index].count)
+               __clear_bit(index, &napi->gro_bitmask);
 }
 
 /* napi->gro_hash[].list contains packets ordered by age.
@@ -5295,8 +5297,10 @@ void napi_gro_flush(struct napi_struct *napi, bool flush_old)
 {
        u32 i;
 
-       for (i = 0; i < GRO_HASH_BUCKETS; i++)
-               __napi_gro_flush_chain(napi, i, flush_old);
+       for (i = 0; i < GRO_HASH_BUCKETS; i++) {
+               if (test_bit(i, &napi->gro_bitmask))
+                       __napi_gro_flush_chain(napi, i, flush_old);
+       }
 }
 EXPORT_SYMBOL(napi_gro_flush);
 
@@ -5388,8 +5392,8 @@ static void gro_flush_oldest(struct list_head *head)
        if (WARN_ON_ONCE(!oldest))
                return;
 
-       /* Do not adjust napi->gro_count, caller is adding a new SKB to
-        * the chain.
+       /* Do not adjust napi->gro_hash[].count, caller is adding a new
+        * SKB to the chain.
         */
        list_del(&oldest->list);
        napi_gro_complete(oldest);
@@ -5464,7 +5468,6 @@ static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff
                list_del(&pp->list);
                pp->next = NULL;
                napi_gro_complete(pp);
-               napi->gro_count--;
                napi->gro_hash[hash].count--;
        }
 
@@ -5477,7 +5480,6 @@ static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff
        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;
@@ -5492,6 +5494,13 @@ pull:
        if (grow > 0)
                gro_pull_from_frag0(skb, grow);
 ok:
+       if (napi->gro_hash[hash].count) {
+               if (!test_bit(hash, &napi->gro_bitmask))
+                       __set_bit(hash, &napi->gro_bitmask);
+       } else if (test_bit(hash, &napi->gro_bitmask)) {
+               __clear_bit(hash, &napi->gro_bitmask);
+       }
+
        return ret;
 
 normal:
@@ -5890,7 +5899,7 @@ bool napi_complete_done(struct napi_struct *n, int work_done)
                                 NAPIF_STATE_IN_BUSY_POLL)))
                return false;
 
-       if (n->gro_count) {
+       if (n->gro_bitmask) {
                unsigned long timeout = 0;
 
                if (work_done)
@@ -6099,7 +6108,7 @@ static enum hrtimer_restart napi_watchdog(struct hrtimer *timer)
        /* Note : we use a relaxed variant of napi_schedule_prep() not setting
         * NAPI_STATE_MISSED, since we do not react to a device IRQ.
         */
-       if (napi->gro_count && !napi_disable_pending(napi) &&
+       if (napi->gro_bitmask && !napi_disable_pending(napi) &&
            !test_and_set_bit(NAPI_STATE_SCHED, &napi->state))
                __napi_schedule_irqoff(napi);
 
@@ -6114,7 +6123,7 @@ void netif_napi_add(struct net_device *dev, struct napi_struct *napi,
        INIT_LIST_HEAD(&napi->poll_list);
        hrtimer_init(&napi->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_PINNED);
        napi->timer.function = napi_watchdog;
-       napi->gro_count = 0;
+       napi->gro_bitmask = 0;
        for (i = 0; i < GRO_HASH_BUCKETS; i++) {
                INIT_LIST_HEAD(&napi->gro_hash[i].list);
                napi->gro_hash[i].count = 0;
@@ -6174,7 +6183,7 @@ void netif_napi_del(struct napi_struct *napi)
        napi_free_frags(napi);
 
        flush_gro_hash(napi);
-       napi->gro_count = 0;
+       napi->gro_bitmask = 0;
 }
 EXPORT_SYMBOL(netif_napi_del);
 
@@ -6216,7 +6225,7 @@ static int napi_poll(struct napi_struct *n, struct list_head *repoll)
                goto out_unlock;
        }
 
-       if (n->gro_count) {
+       if (n->gro_bitmask) {
                /* flush too old packets
                 * If HZ < 1000, flush all packets.
                 */
@@ -9272,6 +9281,9 @@ static struct hlist_head * __net_init netdev_create_hash(void)
 /* Initialize per network namespace state */
 static int __net_init netdev_init(struct net *net)
 {
+       BUILD_BUG_ON(GRO_HASH_BUCKETS >
+                       FIELD_SIZEOF(struct napi_struct, gro_bitmask));
+
        if (net != &init_net)
                INIT_LIST_HEAD(&net->dev_base_head);