Merge branch 'inet-factorize-sk_wmem_alloc-updates'

Eric Dumazet says: ==================== inet: factorize sk_wmem_alloc updates While testing my inet defrag changes, I found that senders could spend ~20% of cpu cycles in skb_set_owner_w() updating sk->sk_wmem_alloc for every fragment they cook, competing with TX completion of prior skbs possibly happening on another cpus. One solution to this problem is to use alloc_skb() instead of sock_wmalloc() and manually perform a single sk_wmem_alloc change. This greatly increases speed for applications sending big UDP datagrams. ==================== Signed-off-by: David S. Miller <[email protected]>
ambv · Apr 1, 2018 · 16c3c91 · 16c3c91
2 parents c072550 + 1f4c6eb
commit 16c3c91
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Showing 2 changed files with 24 additions and 10 deletions.
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
@@ -876,6 +876,7 @@ static int __ip_append_data(struct sock *sk,
 	unsigned int maxfraglen, fragheaderlen, maxnonfragsize;
 	int csummode = CHECKSUM_NONE;
 	struct rtable *rt = (struct rtable *)cork->dst;
+	unsigned int wmem_alloc_delta = 0;
 	u32 tskey = 0;
 
 	skb = skb_peek_tail(queue);
@@ -971,11 +972,10 @@ static int __ip_append_data(struct sock *sk,
 						(flags & MSG_DONTWAIT), &err);
 			} else {
 				skb = NULL;
-				if (refcount_read(&sk->sk_wmem_alloc) <=
+				if (refcount_read(&sk->sk_wmem_alloc) + wmem_alloc_delta <=
 				    2 * sk->sk_sndbuf)
-					skb = sock_wmalloc(sk,
-							   alloclen + hh_len + 15, 1,
-							   sk->sk_allocation);
+					skb = alloc_skb(alloclen + hh_len + 15,
+							sk->sk_allocation);
 				if (unlikely(!skb))
 					err = -ENOBUFS;
 			}
@@ -1033,6 +1033,11 @@ static int __ip_append_data(struct sock *sk,
 			/*
 			 * Put the packet on the pending queue.
 			 */
+			if (!skb->destructor) {
+				skb->destructor = sock_wfree;
+				skb->sk = sk;
+				wmem_alloc_delta += skb->truesize;
+			}
 			__skb_queue_tail(queue, skb);
 			continue;
 		}
@@ -1079,19 +1084,21 @@ static int __ip_append_data(struct sock *sk,
 			skb->len += copy;
 			skb->data_len += copy;
 			skb->truesize += copy;
-			refcount_add(copy, &sk->sk_wmem_alloc);
+			wmem_alloc_delta += copy;
 		}
 		offset += copy;
 		length -= copy;
 	}
 
+	refcount_add(wmem_alloc_delta, &sk->sk_wmem_alloc);
 	return 0;
 
 error_efault:
 	err = -EFAULT;
 error:
 	cork->length -= length;
 	IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
+	refcount_add(wmem_alloc_delta, &sk->sk_wmem_alloc);
 	return err;
 }
 

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
@@ -1259,6 +1259,7 @@ static int __ip6_append_data(struct sock *sk,
 	struct ipv6_txoptions *opt = v6_cork->opt;
 	int csummode = CHECKSUM_NONE;
 	unsigned int maxnonfragsize, headersize;
+	unsigned int wmem_alloc_delta = 0;
 
 	skb = skb_peek_tail(queue);
 	if (!skb) {
@@ -1411,11 +1412,10 @@ static int __ip6_append_data(struct sock *sk,
 						(flags & MSG_DONTWAIT), &err);
 			} else {
 				skb = NULL;
-				if (refcount_read(&sk->sk_wmem_alloc) <=
+				if (refcount_read(&sk->sk_wmem_alloc) + wmem_alloc_delta <=
 				    2 * sk->sk_sndbuf)
-					skb = sock_wmalloc(sk,
-							   alloclen + hh_len, 1,
-							   sk->sk_allocation);
+					skb = alloc_skb(alloclen + hh_len,
+							sk->sk_allocation);
 				if (unlikely(!skb))
 					err = -ENOBUFS;
 			}
@@ -1474,6 +1474,11 @@ static int __ip6_append_data(struct sock *sk,
 			/*
 			 * Put the packet on the pending queue
 			 */
+			if (!skb->destructor) {
+				skb->destructor = sock_wfree;
+				skb->sk = sk;
+				wmem_alloc_delta += skb->truesize;
+			}
 			__skb_queue_tail(queue, skb);
 			continue;
 		}
@@ -1520,19 +1525,21 @@ static int __ip6_append_data(struct sock *sk,
 			skb->len += copy;
 			skb->data_len += copy;
 			skb->truesize += copy;
-			refcount_add(copy, &sk->sk_wmem_alloc);
+			wmem_alloc_delta += copy;
 		}
 		offset += copy;
 		length -= copy;
 	}
 
+	refcount_add(wmem_alloc_delta, &sk->sk_wmem_alloc);
 	return 0;
 
 error_efault:
 	err = -EFAULT;
 error:
 	cork->length -= length;
 	IP6_INC_STATS(sock_net(sk), rt->rt6i_idev, IPSTATS_MIB_OUTDISCARDS);
+	refcount_add(wmem_alloc_delta, &sk->sk_wmem_alloc);
 	return err;
 }