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 <[email protected]>
---
net/ipv4/tcp.c | 10 +++++++---
1 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 934396b..36f6b64 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1105,6 +1105,8 @@ int tcp_recvmsg(struct kiocb *iocb, stru
long timeo;
struct task_struct *user_recv = NULL;
int copied_early = 0;
+ int available = 0;
+ struct sk_buff *skb;
lock_sock(sk);
@@ -1131,7 +1133,11 @@ int tcp_recvmsg(struct kiocb *iocb, stru
#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);
@@ -1140,7 +1146,6 @@ int tcp_recvmsg(struct kiocb *iocb, stru
#endif
do {
- struct sk_buff *skb;
u32 offset;
/* Are we at urgent data? Stop if we have read anything or have SIGURG pending. */
@@ -1428,7 +1433,6 @@ 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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