• Francis Yan's avatar
    tcp: SOF_TIMESTAMPING_OPT_STATS option for SO_TIMESTAMPING · 1c885808
    Francis Yan authored
    This patch exports the sender chronograph stats via the socket
    SO_TIMESTAMPING channel. Currently we can instrument how long a
    particular application unit of data was queued in TCP by tracking
    SOF_TIMESTAMPING_TX_SOFTWARE and SOF_TIMESTAMPING_TX_SCHED. Having
    these sender chronograph stats exported simultaneously along with
    these timestamps allow further breaking down the various sender
    limitation.  For example, a video server can tell if a particular
    chunk of video on a connection takes a long time to deliver because
    TCP was experiencing small receive window. It is not possible to
    tell before this patch without packet traces.
    
    To prepare these stats, the user needs to set
    SOF_TIMESTAMPING_OPT_STATS and SOF_TIMESTAMPING_OPT_TSONLY flags
    while requesting other SOF_TIMESTAMPING TX timestamps. When the
    timestamps are available in the error queue, the stats are returned
    in a separate control message of type SCM_TIMESTAMPING_OPT_STATS,
    in a list of TLVs (struct nlattr) of types: TCP_NLA_BUSY_TIME,
    TCP_NLA_RWND_LIMITED, TCP_NLA_SNDBUF_LIMITED. Unit is microsecond.
    Signed-off-by: default avatarFrancis Yan <francisyyan@gmail.com>
    Signed-off-by: default avatarYuchung Cheng <ycheng@google.com>
    Signed-off-by: default avatarSoheil Hassas Yeganeh <soheil@google.com>
    Acked-by: default avatarNeal Cardwell <ncardwell@google.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    1c885808
socket.h 3.1 KB