Messages in this thread Patch in this message | | | From | Yafang Shao <> | Subject | [PATCH v2 net-next] net: introduce a new tracepoint for tcp_rcv_space_adjust | Date | Wed, 18 Apr 2018 00:36:56 +0800 |
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tcp_rcv_space_adjust is called every time data is copied to user space, introducing a tcp tracepoint for which could show us when the packet is copied to user. This could help us figure out whether there's latency in user process.
When a tcp packet arrives, tcp_rcv_established() will be called and with the existed tracepoint tcp_probe we could get the time when this packet arrives. Then this packet will be copied to user, and tcp_rcv_space_adjust will be called and with this new introduced tracepoint we could get the time when this packet is copied to user.
arrives time : user process time => latency caused by user tcp_probe tcp_rcv_space_adjust
Hence in the printk message, sk_cookie is printed as a key to relate tcp_rcv_space_adjust with tcp_probe.
Maybe we could export sockfd in this new tracepoint as well, then we could relate this new tracepoint with epoll/read/recv* tracepoints, and finally that could show us the whole lifespan of this packet. But we could also implement that with pid as these functions are executed in process context.
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
--- v1 -> v2: use sk_cookie as key suggested by Eric. --- include/trace/events/tcp.h | 33 +++++++++++++++++++++++++++------ net/ipv4/tcp_input.c | 2 ++ 2 files changed, 29 insertions(+), 6 deletions(-)
diff --git a/include/trace/events/tcp.h b/include/trace/events/tcp.h index 3dd6802..814f754 100644 --- a/include/trace/events/tcp.h +++ b/include/trace/events/tcp.h @@ -10,6 +10,7 @@ #include <linux/tracepoint.h> #include <net/ipv6.h> #include <net/tcp.h> +#include <linux/sock_diag.h> #define TP_STORE_V4MAPPED(__entry, saddr, daddr) \ do { \ @@ -125,6 +126,7 @@ __array(__u8, daddr, 4) __array(__u8, saddr_v6, 16) __array(__u8, daddr_v6, 16) + __field(__u64, sock_cookie) ), TP_fast_assign( @@ -144,12 +146,24 @@ TP_STORE_ADDRS(__entry, inet->inet_saddr, inet->inet_daddr, sk->sk_v6_rcv_saddr, sk->sk_v6_daddr); + + /* + * sk_cookie is used to identify a socket, with which we could + * relate this tracepoint with other tracepoints, + * i.e. tcp_probe. + * If we needn't this relation, then sk_cookie is useless; + * if we need this relation, then tcp_probe is already set, + * and sk_cookie is already set in tcp_probe, so we could get + * the value directly. + */ + __entry->sock_cookie = atomic64_read(&sk->sk_cookie); ), - TP_printk("sport=%hu dport=%hu saddr=%pI4 daddr=%pI4 saddrv6=%pI6c daddrv6=%pI6c", + TP_printk("sport=%hu dport=%hu saddr=%pI4 daddr=%pI4 saddrv6=%pI6c daddrv6=%pI6c sock_cookie=%llu", __entry->sport, __entry->dport, __entry->saddr, __entry->daddr, - __entry->saddr_v6, __entry->daddr_v6) + __entry->saddr_v6, __entry->daddr_v6, + __entry->sock_cookie) ); DEFINE_EVENT(tcp_event_sk, tcp_receive_reset, @@ -166,6 +180,13 @@ TP_ARGS(sk) ); +DEFINE_EVENT(tcp_event_sk, tcp_rcv_space_adjust, + + TP_PROTO(const struct sock *sk), + + TP_ARGS(sk) +); + TRACE_EVENT(tcp_retransmit_synack, TP_PROTO(const struct sock *sk, const struct request_sock *req), @@ -232,6 +253,7 @@ __field(__u32, snd_wnd) __field(__u32, srtt) __field(__u32, rcv_wnd) + __field(__u64, sock_cookie) ), TP_fast_assign( @@ -256,15 +278,14 @@ __entry->rcv_wnd = tp->rcv_wnd; __entry->ssthresh = tcp_current_ssthresh(sk); __entry->srtt = tp->srtt_us >> 3; + __entry->sock_cookie = sock_gen_cookie(sk); ), - TP_printk("src=%pISpc dest=%pISpc mark=%#x length=%d snd_nxt=%#x " - "snd_una=%#x snd_cwnd=%u ssthresh=%u snd_wnd=%u srtt=%u " - "rcv_wnd=%u", + TP_printk("src=%pISpc dest=%pISpc mark=%#x length=%d snd_nxt=%#x snd_una=%#x snd_cwnd=%u ssthresh=%u snd_wnd=%u srtt=%u rcv_wnd=%u sock_cookie=%llu", __entry->saddr, __entry->daddr, __entry->mark, __entry->length, __entry->snd_nxt, __entry->snd_una, __entry->snd_cwnd, __entry->ssthresh, __entry->snd_wnd, - __entry->srtt, __entry->rcv_wnd) + __entry->srtt, __entry->rcv_wnd, __entry->sock_cookie) ); #endif /* _TRACE_TCP_H */ diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index f93687f..43ad468 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -582,6 +582,8 @@ void tcp_rcv_space_adjust(struct sock *sk) u32 copied; int time; + trace_tcp_rcv_space_adjust(sk); + tcp_mstamp_refresh(tp); time = tcp_stamp_us_delta(tp->tcp_mstamp, tp->rcvq_space.time); if (time < (tp->rcv_rtt_est.rtt_us >> 3) || tp->rcv_rtt_est.rtt_us == 0) -- 1.8.3.1
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