From 6f458dfb409272082c9bfa412f77ff2fc21c626f Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 20 Jul 2012 05:45:50 +0000 Subject: tcp: improve latencies of timer triggered events Modern TCP stack highly depends on tcp_write_timer() having a small latency, but current implementation doesn't exactly meet the expectations. When a timer fires but finds the socket is owned by the user, it rearms itself for an additional delay hoping next run will be more successful. tcp_write_timer() for example uses a 50ms delay for next try, and it defeats many attempts to get predictable TCP behavior in term of latencies. Use the recently introduced tcp_release_cb(), so that the user owning the socket will call various handlers right before socket release. This will permit us to post a followup patch to address the tcp_tso_should_defer() syndrome (some deferred packets have to wait RTO timer to be transmitted, while cwnd should allow us to send them sooner) Signed-off-by: Eric Dumazet Cc: Tom Herbert Cc: Yuchung Cheng Cc: Neal Cardwell Cc: Nandita Dukkipati Cc: H.K. Jerry Chu Cc: John Heffner Signed-off-by: David S. Miller --- include/linux/tcp.h | 4 +++- include/net/tcp.h | 2 ++ 2 files changed, 5 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/linux/tcp.h b/include/linux/tcp.h index 9febfb685c33..2761856987b2 100644 --- a/include/linux/tcp.h +++ b/include/linux/tcp.h @@ -515,7 +515,9 @@ struct tcp_sock { enum tsq_flags { TSQ_THROTTLED, TSQ_QUEUED, - TSQ_OWNED, /* tcp_tasklet_func() found socket was locked */ + TCP_TSQ_DEFERRED, /* tcp_tasklet_func() found socket was owned */ + TCP_WRITE_TIMER_DEFERRED, /* tcp_write_timer() found socket was owned */ + TCP_DELACK_TIMER_DEFERRED, /* tcp_delack_timer() found socket was owned */ }; static inline struct tcp_sock *tcp_sk(const struct sock *sk) diff --git a/include/net/tcp.h b/include/net/tcp.h index bc7c134ec054..e19124b84cd2 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -350,6 +350,8 @@ extern int tcp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg, extern int tcp_sendpage(struct sock *sk, struct page *page, int offset, size_t size, int flags); extern void tcp_release_cb(struct sock *sk); +extern void tcp_write_timer_handler(struct sock *sk); +extern void tcp_delack_timer_handler(struct sock *sk); extern int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg); extern int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb, const struct tcphdr *th, unsigned int len); -- cgit v1.2.3