Commit 2b1244a4 authored by Chris Leech's avatar Chris Leech Committed by Dan Williams
Browse files

I/OAT: Only offload copies for TCP when there will be a context switch 


The performance wins come with having the DMA copy engine doing the copies
in parallel with the context switch.  If there is enough data ready on the
socket at recv time just use a regular copy.

Signed-off-by: default avatarChris Leech <christopher.leech@intel.com>
parent 72d0b7a8

net/ipv4/tcp.c

+7 −3
Original line number Diff line number Diff line
@@ -1116,6 +1116,8 @@ int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg, 
	long timeo;

	struct task_struct *user_recv = NULL;

	int copied_early = 0;

	int available = 0;

	struct sk_buff *skb;



	lock_sock(sk);
@@ -1142,7 +1144,11 @@ int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg, 
#ifdef CONFIG_NET_DMA

	tp->ucopy.dma_chan = NULL;

	preempt_disable();

	if ((len > sysctl_tcp_dma_copybreak) && !(flags & MSG_PEEK) &&

	skb = skb_peek_tail(&sk->sk_receive_queue);

	if (skb)

		available = TCP_SKB_CB(skb)->seq + skb->len - (*seq);

	if ((available < target) &&

	    (len > sysctl_tcp_dma_copybreak) && !(flags & MSG_PEEK) &&

	    !sysctl_tcp_low_latency && __get_cpu_var(softnet_data).net_dma) {

		preempt_enable_no_resched();

		tp->ucopy.pinned_list = dma_pin_iovec_pages(msg->msg_iov, len);
@@ -1151,7 +1157,6 @@ int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg, 
#endif



	do {

		struct sk_buff *skb;

		u32 offset;



		/* Are we at urgent data? Stop if we have read anything or have SIGURG pending. */
@@ -1439,7 +1444,6 @@ skip_copy: 


#ifdef CONFIG_NET_DMA

	if (tp->ucopy.dma_chan) {

		struct sk_buff *skb;

		dma_cookie_t done, used;



		dma_async_memcpy_issue_pending(tp->ucopy.dma_chan);

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