Commit 2e77d89b authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net: avoid a pair of dst_hold()/dst_release() in ip_append_data() 



We can reduce pressure on dst entry refcount that slowdown UDP transmit
path on SMP machines. This pressure is visible on RTP servers when
delivering content to mediagateways, especially big ones, handling
thousand of streams. Several cpus send UDP frames to the same
destination, hence use the same dst entry.

This patch makes ip_append_data() eventually steal the refcount its
callers had to take on the dst entry.

This doesnt avoid all refcounting, but still gives speedups on SMP,
on UDP/RAW transmit path

Signed-off-by: default avatarEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 4db0acf3

include/net/ip.h

+1 −1
Original line number Original line Diff line number Diff line
@@ -110,7 +110,7 @@ extern int ip_append_data(struct sock *sk, 
						   int odd, struct sk_buff *skb),

						   int odd, struct sk_buff *skb),

				void *from, int len, int protolen,

				void *from, int len, int protolen,

				struct ipcm_cookie *ipc,

				struct ipcm_cookie *ipc,

				struct rtable *rt,

				struct rtable **rt,

				unsigned int flags);

				unsigned int flags);

extern int		ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb);

extern int		ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb);

extern ssize_t		ip_append_page(struct sock *sk, struct page *page,

extern ssize_t		ip_append_page(struct sock *sk, struct page *page,

net/ipv4/icmp.c

+4 −4
Original line number Original line Diff line number Diff line
@@ -321,12 +321,12 @@ static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd, 
}

}





static void icmp_push_reply(struct icmp_bxm *icmp_param,

static void icmp_push_reply(struct icmp_bxm *icmp_param,

			    struct ipcm_cookie *ipc, struct rtable *rt)

			    struct ipcm_cookie *ipc, struct rtable **rt)

{

{

	struct sock *sk;

	struct sock *sk;

	struct sk_buff *skb;

	struct sk_buff *skb;





	sk = icmp_sk(dev_net(rt->u.dst.dev));

	sk = icmp_sk(dev_net((*rt)->u.dst.dev));

	if (ip_append_data(sk, icmp_glue_bits, icmp_param,

	if (ip_append_data(sk, icmp_glue_bits, icmp_param,

			   icmp_param->data_len+icmp_param->head_len,

			   icmp_param->data_len+icmp_param->head_len,

			   icmp_param->head_len,

			   icmp_param->head_len,
@@ -392,7 +392,7 @@ static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb) 
	}

	}

	if (icmpv4_xrlim_allow(net, rt, icmp_param->data.icmph.type,

	if (icmpv4_xrlim_allow(net, rt, icmp_param->data.icmph.type,

			       icmp_param->data.icmph.code))

			       icmp_param->data.icmph.code))

		icmp_push_reply(icmp_param, &ipc, rt);

		icmp_push_reply(icmp_param, &ipc, &rt);

	ip_rt_put(rt);

	ip_rt_put(rt);

out_unlock:

out_unlock:

	icmp_xmit_unlock(sk);

	icmp_xmit_unlock(sk);
@@ -635,7 +635,7 @@ route_done: 
		icmp_param.data_len = room;

		icmp_param.data_len = room;

	icmp_param.head_len = sizeof(struct icmphdr);

	icmp_param.head_len = sizeof(struct icmphdr);





	icmp_push_reply(&icmp_param, &ipc, rt);

	icmp_push_reply(&icmp_param, &ipc, &rt);

ende:

ende:

	ip_rt_put(rt);

	ip_rt_put(rt);

out_unlock:

out_unlock:

net/ipv4/ip_output.c

+8 −3
Original line number Original line Diff line number Diff line
@@ -778,7 +778,7 @@ int ip_append_data(struct sock *sk, 
		   int getfrag(void *from, char *to, int offset, int len,

		   int getfrag(void *from, char *to, int offset, int len,

			       int odd, struct sk_buff *skb),

			       int odd, struct sk_buff *skb),

		   void *from, int length, int transhdrlen,

		   void *from, int length, int transhdrlen,

		   struct ipcm_cookie *ipc, struct rtable *rt,

		   struct ipcm_cookie *ipc, struct rtable **rtp,

		   unsigned int flags)

		   unsigned int flags)

{

{

	struct inet_sock *inet = inet_sk(sk);

	struct inet_sock *inet = inet_sk(sk);
@@ -793,6 +793,7 @@ int ip_append_data(struct sock *sk, 
	int offset = 0;

	int offset = 0;

	unsigned int maxfraglen, fragheaderlen;

	unsigned int maxfraglen, fragheaderlen;

	int csummode = CHECKSUM_NONE;

	int csummode = CHECKSUM_NONE;

	struct rtable *rt;





	if (flags&MSG_PROBE)

	if (flags&MSG_PROBE)

		return 0;

		return 0;
@@ -812,7 +813,11 @@ int ip_append_data(struct sock *sk, 
			inet->cork.flags |= IPCORK_OPT;

			inet->cork.flags |= IPCORK_OPT;

			inet->cork.addr = ipc->addr;

			inet->cork.addr = ipc->addr;

		}

		}

		dst_hold(&rt->u.dst);

		rt = *rtp;

		/*

		 * We steal reference to this route, caller should not release it

		 */

		*rtp = NULL;

		inet->cork.fragsize = mtu = inet->pmtudisc == IP_PMTUDISC_PROBE ?

		inet->cork.fragsize = mtu = inet->pmtudisc == IP_PMTUDISC_PROBE ?

					    rt->u.dst.dev->mtu :

					    rt->u.dst.dev->mtu :

					    dst_mtu(rt->u.dst.path);

					    dst_mtu(rt->u.dst.path);
@@ -1391,7 +1396,7 @@ void ip_send_reply(struct sock *sk, struct sk_buff *skb, struct ip_reply_arg *ar 
	sk->sk_protocol = ip_hdr(skb)->protocol;

	sk->sk_protocol = ip_hdr(skb)->protocol;

	sk->sk_bound_dev_if = arg->bound_dev_if;

	sk->sk_bound_dev_if = arg->bound_dev_if;

	ip_append_data(sk, ip_reply_glue_bits, arg->iov->iov_base, len, 0,

	ip_append_data(sk, ip_reply_glue_bits, arg->iov->iov_base, len, 0,

		       &ipc, rt, MSG_DONTWAIT);

		       &ipc, &rt, MSG_DONTWAIT);

	if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {

	if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {

		if (arg->csumoffset >= 0)

		if (arg->csumoffset >= 0)

			*((__sum16 *)skb_transport_header(skb) +

			*((__sum16 *)skb_transport_header(skb) +

net/ipv4/raw.c

+1 −1
Original line number Original line Diff line number Diff line
@@ -572,7 +572,7 @@ back_from_confirm: 
			ipc.addr = rt->rt_dst;

			ipc.addr = rt->rt_dst;

		lock_sock(sk);

		lock_sock(sk);

		err = ip_append_data(sk, ip_generic_getfrag, msg->msg_iov, len, 0,

		err = ip_append_data(sk, ip_generic_getfrag, msg->msg_iov, len, 0,

					&ipc, rt, msg->msg_flags);

					&ipc, &rt, msg->msg_flags);

		if (err)

		if (err)

			ip_flush_pending_frames(sk);

			ip_flush_pending_frames(sk);

		else if (!(msg->msg_flags & MSG_MORE))

		else if (!(msg->msg_flags & MSG_MORE))

net/ipv4/udp.c

+1 −1
Original line number Original line Diff line number Diff line
@@ -719,7 +719,7 @@ do_append_data: 
	up->len += ulen;

	up->len += ulen;

	getfrag  =  is_udplite ?  udplite_getfrag : ip_generic_getfrag;

	getfrag  =  is_udplite ?  udplite_getfrag : ip_generic_getfrag;

	err = ip_append_data(sk, getfrag, msg->msg_iov, ulen,

	err = ip_append_data(sk, getfrag, msg->msg_iov, ulen,

			sizeof(struct udphdr), &ipc, rt,

			sizeof(struct udphdr), &ipc, &rt,

			corkreq ? msg->msg_flags|MSG_MORE : msg->msg_flags);

			corkreq ? msg->msg_flags|MSG_MORE : msg->msg_flags);

	if (err)

	if (err)

		udp_flush_pending_frames(sk);

		udp_flush_pending_frames(sk);

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