This patch set provides instrumentation on TCP sender limitations. While developing the BBR congestion control, we noticed that TCP sending process is often limited by factors unrelated to congestion control: insufficient sender buffer and/or insufficient receive window/buffer to saturate the network bandwidth. Unfortunately these limits are not visible to the users and often the poor performance is attributed to the congestion control of choice.
Thie patch aims to help users get the high level understanding of where sending process is limited by, similar to the TCP_INFO design. It is not to replace detailed kernel tracing and instrumentation facilities. In addition this patch set provide a new option to the timestamping work to instrument these limits on application data unit. For exampe, one can use SO_TIMESTAMPING and this patch set to measure the how long a particular HTTP response is limited by small receive window. Patch set was initially written by Francis Yan then polished by Yuchung Cheng, with lots of help from Eric Dumazet and Soheil Hassas Yeganeh. Francis Yan (6): tcp: instrument tcp sender limits chronographs tcp: instrument how long TCP is busy sending tcp: instrument how long TCP is limited by receive window tcp: instrument how long TCP is limited by insufficient send buffer tcp: export sender limits chronographs to TCP_INFO tcp: SOF_TIMESTAMPING_OPT_STATS option for SO_TIMESTAMPING Documentation/networking/timestamping.txt | 10 +++++ arch/alpha/include/uapi/asm/socket.h | 2 + arch/frv/include/uapi/asm/socket.h | 2 + arch/ia64/include/uapi/asm/socket.h | 2 + arch/m32r/include/uapi/asm/socket.h | 2 + arch/mips/include/uapi/asm/socket.h | 2 + arch/mn10300/include/uapi/asm/socket.h | 2 + arch/parisc/include/uapi/asm/socket.h | 2 + arch/powerpc/include/uapi/asm/socket.h | 2 + arch/s390/include/uapi/asm/socket.h | 2 + arch/sparc/include/uapi/asm/socket.h | 2 + arch/xtensa/include/uapi/asm/socket.h | 2 + include/linux/tcp.h | 9 ++++- include/net/tcp.h | 20 +++++++++- include/uapi/asm-generic/socket.h | 2 + include/uapi/linux/net_tstamp.h | 3 +- include/uapi/linux/tcp.h | 12 ++++++ net/core/skbuff.c | 14 +++++-- net/core/sock.c | 7 ++++ net/ipv4/tcp.c | 50 ++++++++++++++++++++++- net/ipv4/tcp_input.c | 8 +++- net/ipv4/tcp_output.c | 66 ++++++++++++++++++++++++++++++- net/socket.c | 7 +++- 23 files changed, 217 insertions(+), 13 deletions(-) -- 2.8.0.rc3.226.g39d4020
