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

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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: Chris Leech <christopher.leech@intel.com>
This commit is contained in:
Chris Leech 2007-03-08 09:57:36 -08:00 committed by Dan Williams
parent 72d0b7a81d
commit 2b1244a43b
1 changed files with 7 additions and 3 deletions
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10
net/ipv4/tcp.c
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@ -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);