[Dle-develop] PATCH 0/2] Tracepoints for queueing skb to rcvbuf

[Satoru M. <sat...@hd...>]

Hi,

Kernel may drops packets when it queues them to socket receive buffer.
Currently We can detect packet drop events and know when and where it
happened via kfree_skb tracepoint. But it's difficult to know a detailed
reason because there are some possibilities.

In UDP case, core function for queueing skb to socket rcvbuf is
__udp_queue_rcv_skb and its call chain is following:

__udp_queue_rcv_skb
 ip_queue_rcv_skb
  sock_queue_rcv_skb
   sk_rmem_schedule
    __sk_mem_schedule

We can catch a packet drop event in __udp_queue_rcv_skb and it means
ip_queue_rcv_skb/sock_queue_rcv_skb returned negative value.
In sock_queue_rcv_skb there are 3 possibilities-(*) where it returns
negative value but we can't separate them. Moreover sock_queue_rcv_skb calls
__sk_mem_schedule and there are several if satetements to decide whether
kernel should drop the packet.

To separate these reasons, this patchset adds 3 tracepoints.

1st one is added to __udp_queue_rcv_skb to get return value of
ip_queue_rcv_skb. Analyzing it we can separate above (*) (3 possibilities).

2nd and 3rd one are to get more detailed information. We can collect status
of socket receive queue and related parameters(some of them are sysctl knob
e.g. /proc/sys/net/ipv4/udp_mem, etc. for UDP) and then we can tune kernel
behavior easily.

Any comments and feedback are welcome.


Satoru Moriya (2):
  udp: add tracepoint for queueing skb to rcvbuf
  core: add tracepoints for queueing skb to rcvbuf

 include/trace/events/sock.h |   68 +++++++++++++++++++++++++++++++++++++++++++
 include/trace/events/udp.h  |   32 ++++++++++++++++++++
 net/core/net-traces.c       |    2 +
 net/core/sock.c             |    5 +++
 net/ipv4/udp.c              |    2 +
 5 files changed, 109 insertions(+), 0 deletions(-)
 create mode 100644 include/trace/events/sock.h
 create mode 100644 include/trace/events/udp.h