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| author | Francis Yan <francisyyan@gmail.com> | 2016-11-28 08:07:18 +0100 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2016-11-30 16:04:25 +0100 |
| commit | 1c885808e45601b2b6f68b30ac1d999e10b6f606 (patch) | |
| tree | 4878c60feb2769477239b63194ce5946129bcd75 /Documentation/networking/timestamping.txt | |
| parent | tcp: export sender limits chronographs to TCP_INFO (diff) | |
| download | linux-1c885808e45601b2b6f68b30ac1d999e10b6f606.tar.xz linux-1c885808e45601b2b6f68b30ac1d999e10b6f606.zip | |
tcp: SOF_TIMESTAMPING_OPT_STATS option for SO_TIMESTAMPING
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: Francis Yan <francisyyan@gmail.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'Documentation/networking/timestamping.txt')
| -rw-r--r-- | Documentation/networking/timestamping.txt | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/Documentation/networking/timestamping.txt b/Documentation/networking/timestamping.txt index 671cccf0dcd2..96f50694a748 100644 --- a/Documentation/networking/timestamping.txt +++ b/Documentation/networking/timestamping.txt @@ -182,6 +182,16 @@ SOF_TIMESTAMPING_OPT_TSONLY: the timestamp even if sysctl net.core.tstamp_allow_data is 0. This option disables SOF_TIMESTAMPING_OPT_CMSG. +SOF_TIMESTAMPING_OPT_STATS: + + Optional stats that are obtained along with the transmit timestamps. + It must be used together with SOF_TIMESTAMPING_OPT_TSONLY. When the + transmit timestamp is available, the stats are available in a + separate control message of type SCM_TIMESTAMPING_OPT_STATS, as a + list of TLVs (struct nlattr) of types. These stats allow the + application to associate various transport layer stats with + the transmit timestamps, such as how long a certain block of + data was limited by peer's receiver window. New applications are encouraged to pass SOF_TIMESTAMPING_OPT_ID to disambiguate timestamps and SOF_TIMESTAMPING_OPT_TSONLY to operate |