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tcp: instrument how long TCP is busy sending

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This patch measures TCP busy time, which is defined as the period
of time when sender has data (or FIN) to send. The time starts when
data is buffered and stops when the write queue is flushed by ACKs
or error events.

Note the busy time does not include SYN time, unless data is
included in SYN (i.e. Fast Open). It does include FIN time even
if the FIN carries no payload. Excluding pure FIN is possible but
would incur one additional test in the fast path, which may not
be worth it.

Signed-off-by: Francis Yan <francisyyan@gmail.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Francis Yan
2016-11-27 23:07:14 -08:00
committed by David S. Miller
parent 05b055e891
commit 0f87230d1a
3 changed files with 24 additions and 4 deletions
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6
include/net/tcp.h
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@@ -1535,6 +1535,7 @@ static inline void tcp_write_queue_purge(struct sock *sk)
{
struct sk_buff *skb;
tcp_chrono_stop(sk, TCP_CHRONO_BUSY);
while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL)
sk_wmem_free_skb(sk, skb);
sk_mem_reclaim(sk);
@@ -1593,8 +1594,10 @@ static inline void tcp_advance_send_head(struct sock *sk, const struct sk_buff *
static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked)
{
if (sk->sk_send_head == skb_unlinked)
if (sk->sk_send_head == skb_unlinked) {
sk->sk_send_head = NULL;
tcp_chrono_stop(sk, TCP_CHRONO_BUSY);
}
if (tcp_sk(sk)->highest_sack == skb_unlinked)
tcp_sk(sk)->highest_sack = NULL;
}
@@ -1616,6 +1619,7 @@ static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb
/* Queue it, remembering where we must start sending. */
if (sk->sk_send_head == NULL) {
sk->sk_send_head = skb;
tcp_chrono_start(sk, TCP_CHRONO_BUSY);
if (tcp_sk(sk)->highest_sack == NULL)
tcp_sk(sk)->highest_sack = skb;