From: Eric Dumazet <eric.duma...@gmail.com>
Date: Sat, 7 Jul 2018 17:22:01 -0700
> Maybe gro_count should be replaced by a bitmask, so that we can
> speed up napi_gro_flush(), since it now has to use 3 cache lines
> (gro_hash[] size is 192 bytes)
Something like this?
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index b683971e500d..a4d859a7e9de 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -310,7 +310,7 @@ struct gro_list {
/*
* Structure for NAPI scheduling similar to tasklet but with weighting
*/
-#define GRO_HASH_BUCKETS 8
+#define GRO_HASH_BUCKETS 8 /* Must be <= 32 due to gro_mask */
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 +322,7 @@ struct napi_struct {
unsigned long state;
int weight;
- unsigned int gro_count;
+ unsigned int gro_hash_mask;
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 89825c1eccdc..0dfb84a82586 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5158,12 +5158,14 @@ static void __napi_gro_flush_chain(struct napi_struct
*napi, u32 index,
list_for_each_entry_safe_reverse(skb, p, head, list) {
if (flush_old && NAPI_GRO_CB(skb)->age == jiffies)
- return;
+ goto out;
list_del_init(&skb->list);
napi_gro_complete(skb);
- napi->gro_count--;
napi->gro_hash[index].count--;
}
+out:
+ if (list_empty(head))
+ napi->gro_hash_mask &= ~(1 << index);
}
/* napi->gro_hash[].list contains packets ordered by age.
@@ -5174,8 +5176,10 @@ 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 (napi->gro_hash_mask & (1 << i))
+ __napi_gro_flush_chain(napi, i, flush_old);
+ }
}
EXPORT_SYMBOL(napi_gro_flush);
@@ -5267,8 +5271,8 @@ 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_mask, caller is adding a new
+ * SKB to the chain.
*/
list_del(&oldest->list);
napi_gro_complete(oldest);
@@ -5342,8 +5346,9 @@ static enum gro_result dev_gro_receive(struct napi_struct
*napi, struct sk_buff
if (pp) {
list_del_init(&pp->list);
napi_gro_complete(pp);
- napi->gro_count--;
napi->gro_hash[hash].count--;
+ if (list_empty(&napi->gro_hash[hash].list))
+ napi->gro_hash_mask &= ~(1 << hash);
}
if (same_flow)
@@ -5355,7 +5360,7 @@ 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_mask |= (1 << hash);
napi->gro_hash[hash].count++;
}
NAPI_GRO_CB(skb)->count = 1;
@@ -5768,7 +5773,7 @@ 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_hash_mask) {
unsigned long timeout = 0;
if (work_done)
@@ -5977,7 +5982,7 @@ 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_hash_mask && !napi_disable_pending(napi) &&
!test_and_set_bit(NAPI_STATE_SCHED, &napi->state))
__napi_schedule_irqoff(napi);
@@ -5992,7 +5997,7 @@ 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_hash_mask = 0;
for (i = 0; i < GRO_HASH_BUCKETS; i++) {
INIT_LIST_HEAD(&napi->gro_hash[i].list);
napi->gro_hash[i].count = 0;
@@ -6052,7 +6057,7 @@ void netif_napi_del(struct napi_struct *napi)
napi_free_frags(napi);
flush_gro_hash(napi);
- napi->gro_count = 0;
+ napi->gro_hash_mask = 0;
}
EXPORT_SYMBOL(netif_napi_del);
@@ -6094,7 +6099,7 @@ static int napi_poll(struct napi_struct *n, struct
list_head *repoll)
goto out_unlock;
}
- if (n->gro_count) {
+ if (n->gro_hash_mask) {
/* flush too old packets
* If HZ < 1000, flush all packets.
*/
