[PATCH net-next 0/2] udp: do fwd memory scheduling on dequeue

[PATCH net-next 0/2] udp: do fwd memory scheduling on dequeue

[Paolo Abeni]

After commit 850cbaddb52d ("udp: use it's own memory accounting schema"),
the udp code needs to acquire twice the receive queue spinlock on dequeue.

This patch series remove the need for the second lock at skb free time,
moving the udp memory scheduling inside the dequeue operation; the skb
destructor field is not used anymore and an additional sk argument is added
to ip_cmsg_recv_offset() to cope with null skb->sk after dequeue.

Many thanks to Eric Dumazed for suggesting pretty all much the above.

Paolo Abeni (2):
  net/sock: add an explicit sk argument for ip_cmsg_recv_offset()
  udp: do fwd memory scheduling on dequeue

 include/linux/skbuff.h |  4 ++++
 include/net/ip.h       |  5 +++--
 include/net/udp.h      | 15 +++++++++++++++
 net/core/datagram.c    | 17 ++++++++++++-----
 net/ipv4/ip_sockglue.c |  6 +++---
 net/ipv4/udp.c         | 44 +++++++++++++++++++++++++-------------------
 net/ipv6/udp.c         |  5 ++---
 net/rxrpc/input.c      |  7 +++----
 net/sunrpc/svcsock.c   |  2 +-
 net/sunrpc/xprtsock.c  |  2 +-
 net/unix/af_unix.c     |  4 ++--
 11 files changed, 71 insertions(+), 40 deletions(-)

-- 
1.8.3.1

[PATCH net-next v2 1/2] net/sock: add an explicit sk argument for ip_cmsg_recv_offset()

[Paolo Abeni]

So that we can use it even after orphaining the skbuff.

Suggested-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
@Eric, please add your signed off by when you feel comfortable with the patch
as you basically authored it

 include/net/ip.h       | 5 +++--
 net/ipv4/ip_sockglue.c | 6 +++---
 net/ipv4/udp.c         | 2 +-
 net/ipv6/udp.c         | 2 +-
 4 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/include/net/ip.h b/include/net/ip.h
index 5413883..f25c662 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -578,7 +578,8 @@ int ip_options_get_from_user(struct net *net, struct ip_options_rcu **optp,
  */
 
 void ipv4_pktinfo_prepare(const struct sock *sk, struct sk_buff *skb);
-void ip_cmsg_recv_offset(struct msghdr *msg, struct sk_buff *skb, int tlen, int offset);
+void ip_cmsg_recv_offset(struct msghdr *msg, struct sock *sk,
+			 struct sk_buff *skb, int tlen, int offset);
 int ip_cmsg_send(struct sock *sk, struct msghdr *msg,
 		 struct ipcm_cookie *ipc, bool allow_ipv6);
 int ip_setsockopt(struct sock *sk, int level, int optname, char __user *optval,
@@ -600,7 +601,7 @@ void ip_local_error(struct sock *sk, int err, __be32 daddr, __be16 dport,
 
 static inline void ip_cmsg_recv(struct msghdr *msg, struct sk_buff *skb)
 {
-	ip_cmsg_recv_offset(msg, skb, 0, 0);
+	ip_cmsg_recv_offset(msg, skb->sk, skb, 0, 0);
 }
 
 bool icmp_global_allow(void);
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index b8a2d63..940257f 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -153,10 +153,10 @@ static void ip_cmsg_recv_dstaddr(struct msghdr *msg, struct sk_buff *skb)
 	put_cmsg(msg, SOL_IP, IP_ORIGDSTADDR, sizeof(sin), &sin);
 }
 
-void ip_cmsg_recv_offset(struct msghdr *msg, struct sk_buff *skb,
-			 int tlen, int offset)
+void ip_cmsg_recv_offset(struct msghdr *msg, struct sock *sk,
+			 struct sk_buff *skb, int tlen, int offset)
 {
-	struct inet_sock *inet = inet_sk(skb->sk);
+	struct inet_sock *inet = inet_sk(sk);
 	unsigned int flags = inet->cmsg_flags;
 
 	/* Ordered by supposed usage frequency */
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 195992e..55f2d7c 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1420,7 +1420,7 @@ int udp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int noblock,
 		*addr_len = sizeof(*sin);
 	}
 	if (inet->cmsg_flags)
-		ip_cmsg_recv_offset(msg, skb, sizeof(struct udphdr), off);
+		ip_cmsg_recv_offset(msg, sk, skb, sizeof(struct udphdr), off);
 
 	err = copied;
 	if (flags & MSG_TRUNC)
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index a7700bb..cb73533 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -425,7 +425,7 @@ int udpv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 
 	if (is_udp4) {
 		if (inet->cmsg_flags)
-			ip_cmsg_recv_offset(msg, skb,
+			ip_cmsg_recv_offset(msg, sk, skb,
 					    sizeof(struct udphdr), off);
 	} else {
 		if (np->rxopt.all)
-- 
1.8.3.1

[PATCH net-next v2 1/2] net/sock: add an explicit sk argument for ip_cmsg_recv_offset()

[Paolo Abeni]

So that we can use it even after orphaining the skbuff.

Suggested-by: Eric Dumazet <eric.dumazet-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Signed-off-by: Paolo Abeni <pabeni-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
@Eric, please add your signed off by when you feel comfortable with the patch
as you basically authored it

 include/net/ip.h       | 5 +++--
 net/ipv4/ip_sockglue.c | 6 +++---
 net/ipv4/udp.c         | 2 +-
 net/ipv6/udp.c         | 2 +-
 4 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/include/net/ip.h b/include/net/ip.h
index 5413883..f25c662 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -578,7 +578,8 @@ int ip_options_get_from_user(struct net *net, struct ip_options_rcu **optp,
  */
 
 void ipv4_pktinfo_prepare(const struct sock *sk, struct sk_buff *skb);
-void ip_cmsg_recv_offset(struct msghdr *msg, struct sk_buff *skb, int tlen, int offset);
+void ip_cmsg_recv_offset(struct msghdr *msg, struct sock *sk,
+			 struct sk_buff *skb, int tlen, int offset);
 int ip_cmsg_send(struct sock *sk, struct msghdr *msg,
 		 struct ipcm_cookie *ipc, bool allow_ipv6);
 int ip_setsockopt(struct sock *sk, int level, int optname, char __user *optval,
@@ -600,7 +601,7 @@ void ip_local_error(struct sock *sk, int err, __be32 daddr, __be16 dport,
 
 static inline void ip_cmsg_recv(struct msghdr *msg, struct sk_buff *skb)
 {
-	ip_cmsg_recv_offset(msg, skb, 0, 0);
+	ip_cmsg_recv_offset(msg, skb->sk, skb, 0, 0);
 }
 
 bool icmp_global_allow(void);
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index b8a2d63..940257f 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -153,10 +153,10 @@ static void ip_cmsg_recv_dstaddr(struct msghdr *msg, struct sk_buff *skb)
 	put_cmsg(msg, SOL_IP, IP_ORIGDSTADDR, sizeof(sin), &sin);
 }
 
-void ip_cmsg_recv_offset(struct msghdr *msg, struct sk_buff *skb,
-			 int tlen, int offset)
+void ip_cmsg_recv_offset(struct msghdr *msg, struct sock *sk,
+			 struct sk_buff *skb, int tlen, int offset)
 {
-	struct inet_sock *inet = inet_sk(skb->sk);
+	struct inet_sock *inet = inet_sk(sk);
 	unsigned int flags = inet->cmsg_flags;
 
 	/* Ordered by supposed usage frequency */
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 195992e..55f2d7c 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1420,7 +1420,7 @@ int udp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int noblock,
 		*addr_len = sizeof(*sin);
 	}
 	if (inet->cmsg_flags)
-		ip_cmsg_recv_offset(msg, skb, sizeof(struct udphdr), off);
+		ip_cmsg_recv_offset(msg, sk, skb, sizeof(struct udphdr), off);
 
 	err = copied;
 	if (flags & MSG_TRUNC)
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index a7700bb..cb73533 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -425,7 +425,7 @@ int udpv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 
 	if (is_udp4) {
 		if (inet->cmsg_flags)
-			ip_cmsg_recv_offset(msg, skb,
+			ip_cmsg_recv_offset(msg, sk, skb,
 					    sizeof(struct udphdr), off);
 	} else {
 		if (np->rxopt.all)
-- 
1.8.3.1

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Re: [PATCH net-next v2 1/2] net/sock: add an explicit sk argument for ip_cmsg_recv_offset()

[Eric Dumazet]

On Fri, 2016-11-04 at 11:28 +0100, Paolo Abeni wrote:
> So that we can use it even after orphaining the skbuff.
> 
> Suggested-by: Eric Dumazet <eric.dumazet@gmail.com>
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> ---
> @Eric, please add your signed off by when you feel comfortable with the patch
> as you basically authored it

> -void ip_cmsg_recv_offset(struct msghdr *msg, struct sk_buff *skb,
> -			 int tlen, int offset)
> +void ip_cmsg_recv_offset(struct msghdr *msg, struct sock *sk,
> +			 struct sk_buff *skb, int tlen, int offset)
>  {
> -	struct inet_sock *inet = inet_sk(skb->sk);
> +	struct inet_sock *inet = inet_sk(sk);
>  	unsigned int flags = inet->cmsg_flags;

My final version had :

void ip_cmsg_recv_offset(struct msghdr *msg, const struct sock *sk,
                         struct sk_buff *skb, int tlen, int offset)
{
	unsigned int flags = inet_sk(sk)->cmsg_flags;


(Ie not using "struct inet_sock *inet = ...", and a const pointer for
struct sock)

Other than that minor details :

Signed-off-by: Eric Dumazet <edumazet@google.com>

Thanks !

Re: [PATCH net-next v2 1/2] net/sock: add an explicit sk argument for ip_cmsg_recv_offset()

[Eric Dumazet]

On Fri, 2016-11-04 at 11:28 +0100, Paolo Abeni wrote:
> So that we can use it even after orphaining the skbuff.
> 
> Suggested-by: Eric Dumazet <eric.dumazet-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> Signed-off-by: Paolo Abeni <pabeni-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> ---
> @Eric, please add your signed off by when you feel comfortable with the patch
> as you basically authored it

> -void ip_cmsg_recv_offset(struct msghdr *msg, struct sk_buff *skb,
> -			 int tlen, int offset)
> +void ip_cmsg_recv_offset(struct msghdr *msg, struct sock *sk,
> +			 struct sk_buff *skb, int tlen, int offset)
>  {
> -	struct inet_sock *inet = inet_sk(skb->sk);
> +	struct inet_sock *inet = inet_sk(sk);
>  	unsigned int flags = inet->cmsg_flags;

My final version had :

void ip_cmsg_recv_offset(struct msghdr *msg, const struct sock *sk,
                         struct sk_buff *skb, int tlen, int offset)
{
	unsigned int flags = inet_sk(sk)->cmsg_flags;


(Ie not using "struct inet_sock *inet = ...", and a const pointer for
struct sock)

Other than that minor details :

Signed-off-by: Eric Dumazet <edumazet-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>

Thanks !


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[PATCH net-next v2 2/2] udp: do fwd memory scheduling on dequeue

[Paolo Abeni]

A new argument is added to __skb_recv_datagram to provide
an explicit skb destructor, invoked under the receive queue
lock.
The UDP protocol uses such argument to perform memory
reclaiming on dequeue, so that the UDP protocol does not
set anymore skb->desctructor.
Instead explicit memory reclaiming is performed at close() time and
when skbs are removed from the receive queue.
The in kernel UDP protocol users now need to call a
skb_recv_udp() variant instead of skb_recv_datagram() to
properly perform memory accounting on dequeue.

Overall, this allows acquiring only once the receive queue
lock on dequeue.

Tested using pktgen with random src port, 64 bytes packet,
wire-speed on a 10G link as sender and udp_sink as the receiver,
using an l4 tuple rxhash to stress the contention, and one or more
udp_sink instances with reuseport.

nr sinks	vanilla		patched
1		440		560
3		2150		2300
6		3650		3800
9		4450		4600
12		6250		6450

v1 -> v2:
 - do rmem and allocated memory scheduling under the receive lock
 - do bulk scheduling in first_packet_length() and in udp_destruct_sock()
 - avoid the typdef for the dequeue callback

Suggested-by: Eric Dumazet <edumazet@google.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
@Eric, please add your signed off by when you feel comfortable with the patch
as you authored some of the code

 include/linux/skbuff.h |  4 ++++
 include/net/udp.h      | 15 +++++++++++++++
 net/core/datagram.c    | 17 ++++++++++++-----
 net/ipv4/udp.c         | 42 ++++++++++++++++++++++++------------------
 net/ipv6/udp.c         |  3 +--
 net/rxrpc/input.c      |  7 +++----
 net/sunrpc/svcsock.c   |  2 +-
 net/sunrpc/xprtsock.c  |  2 +-
 net/unix/af_unix.c     |  4 ++--
 9 files changed, 63 insertions(+), 33 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index cc6e23e..a4aeeca 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -3033,9 +3033,13 @@ static inline void skb_frag_list_init(struct sk_buff *skb)
 int __skb_wait_for_more_packets(struct sock *sk, int *err, long *timeo_p,
 				const struct sk_buff *skb);
 struct sk_buff *__skb_try_recv_datagram(struct sock *sk, unsigned flags,
+					void (*destructor)(struct sock *sk,
+							   struct sk_buff *skb),
 					int *peeked, int *off, int *err,
 					struct sk_buff **last);
 struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned flags,
+				    void (*destructor)(struct sock *sk,
+						       struct sk_buff *skb),
 				    int *peeked, int *off, int *err);
 struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned flags, int noblock,
 				  int *err);
diff --git a/include/net/udp.h b/include/net/udp.h
index 6134f37..e6e4e19 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -248,6 +248,21 @@ static inline __be16 udp_flow_src_port(struct net *net, struct sk_buff *skb,
 /* net/ipv4/udp.c */
 void skb_consume_udp(struct sock *sk, struct sk_buff *skb, int len);
 int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb);
+void udp_skb_destructor(struct sock *sk, struct sk_buff *skb);
+static inline struct sk_buff *
+__skb_recv_udp(struct sock *sk, unsigned int flags, int noblock, int *peeked,
+	       int *off, int *err)
+{
+	return __skb_recv_datagram(sk, flags | (noblock ? MSG_DONTWAIT : 0),
+				   udp_skb_destructor, peeked, off, err);
+}
+static inline struct sk_buff *skb_recv_udp(struct sock *sk, unsigned int flags,
+					   int noblock, int *err)
+{
+	int peeked, off = 0;
+
+	return __skb_recv_udp(sk, flags, noblock, &peeked, &off, err);
+}
 
 void udp_v4_early_demux(struct sk_buff *skb);
 int udp_get_port(struct sock *sk, unsigned short snum,
diff --git a/net/core/datagram.c b/net/core/datagram.c
index bfb973a..49816af 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -165,6 +165,7 @@ static struct sk_buff *skb_set_peeked(struct sk_buff *skb)
  *	__skb_try_recv_datagram - Receive a datagram skbuff
  *	@sk: socket
  *	@flags: MSG_ flags
+ *	@destructor: invoked under the receive lock on successful dequeue
  *	@peeked: returns non-zero if this packet has been seen before
  *	@off: an offset in bytes to peek skb from. Returns an offset
  *	      within an skb where data actually starts
@@ -197,6 +198,8 @@ static struct sk_buff *skb_set_peeked(struct sk_buff *skb)
  *	the standard around please.
  */
 struct sk_buff *__skb_try_recv_datagram(struct sock *sk, unsigned int flags,
+					void (*destructor)(struct sock *sk,
+							   struct sk_buff *skb),
 					int *peeked, int *off, int *err,
 					struct sk_buff **last)
 {
@@ -241,9 +244,11 @@ struct sk_buff *__skb_try_recv_datagram(struct sock *sk, unsigned int flags,
 				}
 
 				atomic_inc(&skb->users);
-			} else
+			} else {
 				__skb_unlink(skb, queue);
-
+				if (destructor)
+					destructor(sk, skb);
+			}
 			spin_unlock_irqrestore(&queue->lock, cpu_flags);
 			*off = _off;
 			return skb;
@@ -262,6 +267,8 @@ struct sk_buff *__skb_try_recv_datagram(struct sock *sk, unsigned int flags,
 EXPORT_SYMBOL(__skb_try_recv_datagram);
 
 struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags,
+				    void (*destructor)(struct sock *sk,
+						       struct sk_buff *skb),
 				    int *peeked, int *off, int *err)
 {
 	struct sk_buff *skb, *last;
@@ -270,8 +277,8 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags,
 	timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
 
 	do {
-		skb = __skb_try_recv_datagram(sk, flags, peeked, off, err,
-					      &last);
+		skb = __skb_try_recv_datagram(sk, flags, destructor, peeked,
+					      off, err, &last);
 		if (skb)
 			return skb;
 
@@ -290,7 +297,7 @@ struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned int flags,
 	int peeked, off = 0;
 
 	return __skb_recv_datagram(sk, flags | (noblock ? MSG_DONTWAIT : 0),
-				   &peeked, &off, err);
+				   NULL, &peeked, &off, err);
 }
 EXPORT_SYMBOL(skb_recv_datagram);
 
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 55f2d7c..dc7cbe0 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1172,26 +1172,26 @@ int udp_sendpage(struct sock *sk, struct page *page, int offset,
 	return ret;
 }
 
+/* fully reclaim rmem/fwd memory allocated for skb */
 static void udp_rmem_release(struct sock *sk, int size, int partial)
 {
 	int amt;
 
 	atomic_sub(size, &sk->sk_rmem_alloc);
-
-	spin_lock_bh(&sk->sk_receive_queue.lock);
 	sk->sk_forward_alloc += size;
 	amt = (sk->sk_forward_alloc - partial) & ~(SK_MEM_QUANTUM - 1);
 	sk->sk_forward_alloc -= amt;
-	spin_unlock_bh(&sk->sk_receive_queue.lock);
 
 	if (amt)
 		__sk_mem_reduce_allocated(sk, amt >> SK_MEM_QUANTUM_SHIFT);
 }
 
-static void udp_rmem_free(struct sk_buff *skb)
+/* Note: called with sk_receive_queue.lock held */
+void udp_skb_destructor(struct sock *sk, struct sk_buff *skb)
 {
-	udp_rmem_release(skb->sk, skb->truesize, 1);
+	udp_rmem_release(sk, skb->truesize, 1);
 }
+EXPORT_SYMBOL(udp_skb_destructor);
 
 int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb)
 {
@@ -1228,9 +1228,9 @@ int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb)
 
 	sk->sk_forward_alloc -= size;
 
-	/* the skb owner in now the udp socket */
-	skb->sk = sk;
-	skb->destructor = udp_rmem_free;
+	/* no need to setup a destructor, we will explicitly release the
+	 * forward allocated memory on dequeue
+	 */
 	skb->dev = NULL;
 	sock_skb_set_dropcount(sk, skb);
 
@@ -1254,8 +1254,15 @@ int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb)
 static void udp_destruct_sock(struct sock *sk)
 {
 	/* reclaim completely the forward allocated memory */
-	__skb_queue_purge(&sk->sk_receive_queue);
-	udp_rmem_release(sk, 0, 0);
+	unsigned int total = 0;
+	struct sk_buff *skb;
+
+	while ((skb = __skb_dequeue(&sk->sk_receive_queue)) != NULL) {
+		total += skb->truesize;
+		kfree_skb(skb);
+	}
+	udp_rmem_release(sk, total, 0);
+
 	inet_sock_destruct(sk);
 }
 
@@ -1287,12 +1294,11 @@ void skb_consume_udp(struct sock *sk, struct sk_buff *skb, int len)
  */
 static int first_packet_length(struct sock *sk)
 {
-	struct sk_buff_head list_kill, *rcvq = &sk->sk_receive_queue;
+	struct sk_buff_head *rcvq = &sk->sk_receive_queue;
 	struct sk_buff *skb;
+	int total = 0;
 	int res;
 
-	__skb_queue_head_init(&list_kill);
-
 	spin_lock_bh(&rcvq->lock);
 	while ((skb = skb_peek(rcvq)) != NULL &&
 		udp_lib_checksum_complete(skb)) {
@@ -1302,12 +1308,13 @@ static int first_packet_length(struct sock *sk)
 				IS_UDPLITE(sk));
 		atomic_inc(&sk->sk_drops);
 		__skb_unlink(skb, rcvq);
-		__skb_queue_tail(&list_kill, skb);
+		total += skb->truesize;
+		kfree_skb(skb);
 	}
 	res = skb ? skb->len : -1;
+	if (total)
+		udp_rmem_release(sk, total, 1);
 	spin_unlock_bh(&rcvq->lock);
-
-	__skb_queue_purge(&list_kill);
 	return res;
 }
 
@@ -1362,8 +1369,7 @@ int udp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int noblock,
 
 try_again:
 	peeking = off = sk_peek_offset(sk, flags);
-	skb = __skb_recv_datagram(sk, flags | (noblock ? MSG_DONTWAIT : 0),
-				  &peeked, &off, &err);
+	skb = __skb_recv_udp(sk, flags, noblock, &peeked, &off, &err);
 	if (!skb)
 		return err;
 
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index cb73533..8345ac6 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -343,8 +343,7 @@ int udpv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 
 try_again:
 	peeking = off = sk_peek_offset(sk, flags);
-	skb = __skb_recv_datagram(sk, flags | (noblock ? MSG_DONTWAIT : 0),
-				  &peeked, &off, &err);
+	skb = __skb_recv_udp(sk, flags, noblock, &peeked, &off, &err);
 	if (!skb)
 		return err;
 
diff --git a/net/rxrpc/input.c b/net/rxrpc/input.c
index 44fb8d8..4c36112 100644
--- a/net/rxrpc/input.c
+++ b/net/rxrpc/input.c
@@ -1053,7 +1053,7 @@ void rxrpc_data_ready(struct sock *udp_sk)
 
 	ASSERT(!irqs_disabled());
 
-	skb = skb_recv_datagram(udp_sk, 0, 1, &ret);
+	skb = skb_recv_udp(udp_sk, 0, 1, &ret);
 	if (!skb) {
 		if (ret == -EAGAIN)
 			return;
@@ -1075,10 +1075,9 @@ void rxrpc_data_ready(struct sock *udp_sk)
 
 	__UDP_INC_STATS(&init_net, UDP_MIB_INDATAGRAMS, 0);
 
-	/* The socket buffer we have is owned by UDP, with UDP's data all over
-	 * it, but we really want our own data there.
+	/* The UDP protocol already released all skb resources;
+	 * we are free to add our own data there.
 	 */
-	skb_orphan(skb);
 	sp = rxrpc_skb(skb);
 
 	/* dig out the RxRPC connection details */
diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index e2a55dc..78da4ae 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -547,7 +547,7 @@ static int svc_udp_recvfrom(struct svc_rqst *rqstp)
 	err = kernel_recvmsg(svsk->sk_sock, &msg, NULL,
 			     0, 0, MSG_PEEK | MSG_DONTWAIT);
 	if (err >= 0)
-		skb = skb_recv_datagram(svsk->sk_sk, 0, 1, &err);
+		skb = skb_recv_udp(svsk->sk_sk, 0, 1, &err);
 
 	if (skb == NULL) {
 		if (err != -EAGAIN) {
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 1758665..7178d0a 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -1080,7 +1080,7 @@ static void xs_udp_data_receive(struct sock_xprt *transport)
 	if (sk == NULL)
 		goto out;
 	for (;;) {
-		skb = skb_recv_datagram(sk, 0, 1, &err);
+		skb = skb_recv_udp(sk, 0, 1, &err);
 		if (skb != NULL) {
 			xs_udp_data_read_skb(&transport->xprt, sk, skb);
 			consume_skb(skb);
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 145082e..8762018 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -2113,8 +2113,8 @@ static int unix_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
 		mutex_lock(&u->iolock);
 
 		skip = sk_peek_offset(sk, flags);
-		skb = __skb_try_recv_datagram(sk, flags, &peeked, &skip, &err,
-					      &last);
+		skb = __skb_try_recv_datagram(sk, flags, NULL, &peeked, &skip,
+					      &err, &last);
 		if (skb)
 			break;
 
-- 
1.8.3.1

[PATCH net-next v2 2/2] udp: do fwd memory scheduling on dequeue

[Paolo Abeni]

A new argument is added to __skb_recv_datagram to provide
an explicit skb destructor, invoked under the receive queue
lock.
The UDP protocol uses such argument to perform memory
reclaiming on dequeue, so that the UDP protocol does not
set anymore skb->desctructor.
Instead explicit memory reclaiming is performed at close() time and
when skbs are removed from the receive queue.
The in kernel UDP protocol users now need to call a
skb_recv_udp() variant instead of skb_recv_datagram() to
properly perform memory accounting on dequeue.

Overall, this allows acquiring only once the receive queue
lock on dequeue.

Tested using pktgen with random src port, 64 bytes packet,
wire-speed on a 10G link as sender and udp_sink as the receiver,
using an l4 tuple rxhash to stress the contention, and one or more
udp_sink instances with reuseport.

nr sinks	vanilla		patched
1		440		560
3		2150		2300
6		3650		3800
9		4450		4600
12		6250		6450

v1 -> v2:
 - do rmem and allocated memory scheduling under the receive lock
 - do bulk scheduling in first_packet_length() and in udp_destruct_sock()
 - avoid the typdef for the dequeue callback

Suggested-by: Eric Dumazet <edumazet-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Acked-by: Hannes Frederic Sowa <hannes-tFNcAqjVMyqKXQKiL6tip0B+6BGkLq7r@public.gmane.org>
Signed-off-by: Paolo Abeni <pabeni-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
@Eric, please add your signed off by when you feel comfortable with the patch
as you authored some of the code

 include/linux/skbuff.h |  4 ++++
 include/net/udp.h      | 15 +++++++++++++++
 net/core/datagram.c    | 17 ++++++++++++-----
 net/ipv4/udp.c         | 42 ++++++++++++++++++++++++------------------
 net/ipv6/udp.c         |  3 +--
 net/rxrpc/input.c      |  7 +++----
 net/sunrpc/svcsock.c   |  2 +-
 net/sunrpc/xprtsock.c  |  2 +-
 net/unix/af_unix.c     |  4 ++--
 9 files changed, 63 insertions(+), 33 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index cc6e23e..a4aeeca 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -3033,9 +3033,13 @@ static inline void skb_frag_list_init(struct sk_buff *skb)
 int __skb_wait_for_more_packets(struct sock *sk, int *err, long *timeo_p,
 				const struct sk_buff *skb);
 struct sk_buff *__skb_try_recv_datagram(struct sock *sk, unsigned flags,
+					void (*destructor)(struct sock *sk,
+							   struct sk_buff *skb),
 					int *peeked, int *off, int *err,
 					struct sk_buff **last);
 struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned flags,
+				    void (*destructor)(struct sock *sk,
+						       struct sk_buff *skb),
 				    int *peeked, int *off, int *err);
 struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned flags, int noblock,
 				  int *err);
diff --git a/include/net/udp.h b/include/net/udp.h
index 6134f37..e6e4e19 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -248,6 +248,21 @@ static inline __be16 udp_flow_src_port(struct net *net, struct sk_buff *skb,
 /* net/ipv4/udp.c */
 void skb_consume_udp(struct sock *sk, struct sk_buff *skb, int len);
 int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb);
+void udp_skb_destructor(struct sock *sk, struct sk_buff *skb);
+static inline struct sk_buff *
+__skb_recv_udp(struct sock *sk, unsigned int flags, int noblock, int *peeked,
+	       int *off, int *err)
+{
+	return __skb_recv_datagram(sk, flags | (noblock ? MSG_DONTWAIT : 0),
+				   udp_skb_destructor, peeked, off, err);
+}
+static inline struct sk_buff *skb_recv_udp(struct sock *sk, unsigned int flags,
+					   int noblock, int *err)
+{
+	int peeked, off = 0;
+
+	return __skb_recv_udp(sk, flags, noblock, &peeked, &off, err);
+}
 
 void udp_v4_early_demux(struct sk_buff *skb);
 int udp_get_port(struct sock *sk, unsigned short snum,
diff --git a/net/core/datagram.c b/net/core/datagram.c
index bfb973a..49816af 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -165,6 +165,7 @@ static struct sk_buff *skb_set_peeked(struct sk_buff *skb)
  *	__skb_try_recv_datagram - Receive a datagram skbuff
  *	@sk: socket
  *	@flags: MSG_ flags
+ *	@destructor: invoked under the receive lock on successful dequeue
  *	@peeked: returns non-zero if this packet has been seen before
  *	@off: an offset in bytes to peek skb from. Returns an offset
  *	      within an skb where data actually starts
@@ -197,6 +198,8 @@ static struct sk_buff *skb_set_peeked(struct sk_buff *skb)
  *	the standard around please.
  */
 struct sk_buff *__skb_try_recv_datagram(struct sock *sk, unsigned int flags,
+					void (*destructor)(struct sock *sk,
+							   struct sk_buff *skb),
 					int *peeked, int *off, int *err,
 					struct sk_buff **last)
 {
@@ -241,9 +244,11 @@ struct sk_buff *__skb_try_recv_datagram(struct sock *sk, unsigned int flags,
 				}
 
 				atomic_inc(&skb->users);
-			} else
+			} else {
 				__skb_unlink(skb, queue);
-
+				if (destructor)
+					destructor(sk, skb);
+			}
 			spin_unlock_irqrestore(&queue->lock, cpu_flags);
 			*off = _off;
 			return skb;
@@ -262,6 +267,8 @@ struct sk_buff *__skb_try_recv_datagram(struct sock *sk, unsigned int flags,
 EXPORT_SYMBOL(__skb_try_recv_datagram);
 
 struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags,
+				    void (*destructor)(struct sock *sk,
+						       struct sk_buff *skb),
 				    int *peeked, int *off, int *err)
 {
 	struct sk_buff *skb, *last;
@@ -270,8 +277,8 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned int flags,
 	timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
 
 	do {
-		skb = __skb_try_recv_datagram(sk, flags, peeked, off, err,
-					      &last);
+		skb = __skb_try_recv_datagram(sk, flags, destructor, peeked,
+					      off, err, &last);
 		if (skb)
 			return skb;
 
@@ -290,7 +297,7 @@ struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned int flags,
 	int peeked, off = 0;
 
 	return __skb_recv_datagram(sk, flags | (noblock ? MSG_DONTWAIT : 0),
-				   &peeked, &off, err);
+				   NULL, &peeked, &off, err);
 }
 EXPORT_SYMBOL(skb_recv_datagram);
 
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 55f2d7c..dc7cbe0 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1172,26 +1172,26 @@ int udp_sendpage(struct sock *sk, struct page *page, int offset,
 	return ret;
 }
 
+/* fully reclaim rmem/fwd memory allocated for skb */
 static void udp_rmem_release(struct sock *sk, int size, int partial)
 {
 	int amt;
 
 	atomic_sub(size, &sk->sk_rmem_alloc);
-
-	spin_lock_bh(&sk->sk_receive_queue.lock);
 	sk->sk_forward_alloc += size;
 	amt = (sk->sk_forward_alloc - partial) & ~(SK_MEM_QUANTUM - 1);
 	sk->sk_forward_alloc -= amt;
-	spin_unlock_bh(&sk->sk_receive_queue.lock);
 
 	if (amt)
 		__sk_mem_reduce_allocated(sk, amt >> SK_MEM_QUANTUM_SHIFT);
 }
 
-static void udp_rmem_free(struct sk_buff *skb)
+/* Note: called with sk_receive_queue.lock held */
+void udp_skb_destructor(struct sock *sk, struct sk_buff *skb)
 {
-	udp_rmem_release(skb->sk, skb->truesize, 1);
+	udp_rmem_release(sk, skb->truesize, 1);
 }
+EXPORT_SYMBOL(udp_skb_destructor);
 
 int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb)
 {
@@ -1228,9 +1228,9 @@ int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb)
 
 	sk->sk_forward_alloc -= size;
 
-	/* the skb owner in now the udp socket */
-	skb->sk = sk;
-	skb->destructor = udp_rmem_free;
+	/* no need to setup a destructor, we will explicitly release the
+	 * forward allocated memory on dequeue
+	 */
 	skb->dev = NULL;
 	sock_skb_set_dropcount(sk, skb);
 
@@ -1254,8 +1254,15 @@ int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb)
 static void udp_destruct_sock(struct sock *sk)
 {
 	/* reclaim completely the forward allocated memory */
-	__skb_queue_purge(&sk->sk_receive_queue);
-	udp_rmem_release(sk, 0, 0);
+	unsigned int total = 0;
+	struct sk_buff *skb;
+
+	while ((skb = __skb_dequeue(&sk->sk_receive_queue)) != NULL) {
+		total += skb->truesize;
+		kfree_skb(skb);
+	}
+	udp_rmem_release(sk, total, 0);
+
 	inet_sock_destruct(sk);
 }
 
@@ -1287,12 +1294,11 @@ void skb_consume_udp(struct sock *sk, struct sk_buff *skb, int len)
  */
 static int first_packet_length(struct sock *sk)
 {
-	struct sk_buff_head list_kill, *rcvq = &sk->sk_receive_queue;
+	struct sk_buff_head *rcvq = &sk->sk_receive_queue;
 	struct sk_buff *skb;
+	int total = 0;
 	int res;
 
-	__skb_queue_head_init(&list_kill);
-
 	spin_lock_bh(&rcvq->lock);
 	while ((skb = skb_peek(rcvq)) != NULL &&
 		udp_lib_checksum_complete(skb)) {
@@ -1302,12 +1308,13 @@ static int first_packet_length(struct sock *sk)
 				IS_UDPLITE(sk));
 		atomic_inc(&sk->sk_drops);
 		__skb_unlink(skb, rcvq);
-		__skb_queue_tail(&list_kill, skb);
+		total += skb->truesize;
+		kfree_skb(skb);
 	}
 	res = skb ? skb->len : -1;
+	if (total)
+		udp_rmem_release(sk, total, 1);
 	spin_unlock_bh(&rcvq->lock);
-
-	__skb_queue_purge(&list_kill);
 	return res;
 }
 
@@ -1362,8 +1369,7 @@ int udp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int noblock,
 
 try_again:
 	peeking = off = sk_peek_offset(sk, flags);
-	skb = __skb_recv_datagram(sk, flags | (noblock ? MSG_DONTWAIT : 0),
-				  &peeked, &off, &err);
+	skb = __skb_recv_udp(sk, flags, noblock, &peeked, &off, &err);
 	if (!skb)
 		return err;
 
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index cb73533..8345ac6 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -343,8 +343,7 @@ int udpv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 
 try_again:
 	peeking = off = sk_peek_offset(sk, flags);
-	skb = __skb_recv_datagram(sk, flags | (noblock ? MSG_DONTWAIT : 0),
-				  &peeked, &off, &err);
+	skb = __skb_recv_udp(sk, flags, noblock, &peeked, &off, &err);
 	if (!skb)
 		return err;
 
diff --git a/net/rxrpc/input.c b/net/rxrpc/input.c
index 44fb8d8..4c36112 100644
--- a/net/rxrpc/input.c
+++ b/net/rxrpc/input.c
@@ -1053,7 +1053,7 @@ void rxrpc_data_ready(struct sock *udp_sk)
 
 	ASSERT(!irqs_disabled());
 
-	skb = skb_recv_datagram(udp_sk, 0, 1, &ret);
+	skb = skb_recv_udp(udp_sk, 0, 1, &ret);
 	if (!skb) {
 		if (ret == -EAGAIN)
 			return;
@@ -1075,10 +1075,9 @@ void rxrpc_data_ready(struct sock *udp_sk)
 
 	__UDP_INC_STATS(&init_net, UDP_MIB_INDATAGRAMS, 0);
 
-	/* The socket buffer we have is owned by UDP, with UDP's data all over
-	 * it, but we really want our own data there.
+	/* The UDP protocol already released all skb resources;
+	 * we are free to add our own data there.
 	 */
-	skb_orphan(skb);
 	sp = rxrpc_skb(skb);
 
 	/* dig out the RxRPC connection details */
diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index e2a55dc..78da4ae 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -547,7 +547,7 @@ static int svc_udp_recvfrom(struct svc_rqst *rqstp)
 	err = kernel_recvmsg(svsk->sk_sock, &msg, NULL,
 			     0, 0, MSG_PEEK | MSG_DONTWAIT);
 	if (err >= 0)
-		skb = skb_recv_datagram(svsk->sk_sk, 0, 1, &err);
+		skb = skb_recv_udp(svsk->sk_sk, 0, 1, &err);
 
 	if (skb == NULL) {
 		if (err != -EAGAIN) {
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 1758665..7178d0a 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -1080,7 +1080,7 @@ static void xs_udp_data_receive(struct sock_xprt *transport)
 	if (sk == NULL)
 		goto out;
 	for (;;) {
-		skb = skb_recv_datagram(sk, 0, 1, &err);
+		skb = skb_recv_udp(sk, 0, 1, &err);
 		if (skb != NULL) {
 			xs_udp_data_read_skb(&transport->xprt, sk, skb);
 			consume_skb(skb);
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 145082e..8762018 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -2113,8 +2113,8 @@ static int unix_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
 		mutex_lock(&u->iolock);
 
 		skip = sk_peek_offset(sk, flags);
-		skb = __skb_try_recv_datagram(sk, flags, &peeked, &skip, &err,
-					      &last);
+		skb = __skb_try_recv_datagram(sk, flags, NULL, &peeked, &skip,
+					      &err, &last);
 		if (skb)
 			break;
 
-- 
1.8.3.1

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Re: [PATCH net-next v2 2/2] udp: do fwd memory scheduling on dequeue

[Eric Dumazet]

On Fri, 2016-11-04 at 11:28 +0100, Paolo Abeni wrote:
> A new argument is added to __skb_recv_datagram to provide
> an explicit skb destructor, invoked under the receive queue
> lock.
> The UDP protocol uses such argument to perform memory
> reclaiming on dequeue, so that the UDP protocol does not
> set anymore skb->desctructor.
> Instead explicit memory reclaiming is performed at close() time and
> when skbs are removed from the receive queue.
> The in kernel UDP protocol users now need to call a
> skb_recv_udp() variant instead of skb_recv_datagram() to
> properly perform memory accounting on dequeue.
> 
> Overall, this allows acquiring only once the receive queue
> lock on dequeue.
> 
> Tested using pktgen with random src port, 64 bytes packet,
> wire-speed on a 10G link as sender and udp_sink as the receiver,
> using an l4 tuple rxhash to stress the contention, and one or more
> udp_sink instances with reuseport.
> 
> nr sinks	vanilla		patched
> 1		440		560
> 3		2150		2300
> 6		3650		3800
> 9		4450		4600
> 12		6250		6450
> 
> v1 -> v2:
>  - do rmem and allocated memory scheduling under the receive lock
>  - do bulk scheduling in first_packet_length() and in udp_destruct_sock()
>  - avoid the typdef for the dequeue callback
> 
> Suggested-by: Eric Dumazet <edumazet@google.com>
> Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> ---
> @Eric, please add your signed off by when you feel comfortable with the patch
> as you authored some of the code

SGTM, thanks Paolo and Hannes !

Acked-by: Eric Dumazet <edumazet@google.com>

Re: [PATCH net-next 0/2] udp: do fwd memory scheduling on dequeue

[David Miller]

From: Paolo Abeni <pabeni@redhat.com>
Date: Fri,  4 Nov 2016 11:28:57 +0100

> After commit 850cbaddb52d ("udp: use it's own memory accounting schema"),
> the udp code needs to acquire twice the receive queue spinlock on dequeue.
> 
> This patch series remove the need for the second lock at skb free time,
> moving the udp memory scheduling inside the dequeue operation; the skb
> destructor field is not used anymore and an additional sk argument is added
> to ip_cmsg_recv_offset() to cope with null skb->sk after dequeue.
> 
> Many thanks to Eric Dumazed for suggesting pretty all much the above.

Series applied, thanks.

Re: [PATCH net-next 0/2] udp: do fwd memory scheduling on dequeue

[David Miller]

From: Paolo Abeni <pabeni-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Date: Fri,  4 Nov 2016 11:28:57 +0100

> After commit 850cbaddb52d ("udp: use it's own memory accounting schema"),
> the udp code needs to acquire twice the receive queue spinlock on dequeue.
> 
> This patch series remove the need for the second lock at skb free time,
> moving the udp memory scheduling inside the dequeue operation; the skb
> destructor field is not used anymore and an additional sk argument is added
> to ip_cmsg_recv_offset() to cope with null skb->sk after dequeue.
> 
> Many thanks to Eric Dumazed for suggesting pretty all much the above.

Series applied, thanks.
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