NAME

       tcptop - Summarize TCP send/recv throughput by host. Top for TCP.

SYNOPSIS

       tcptop [-h] [-C] [-S] [-p PID] [--cgroupmap MAPPATH]
                 [--mntnsmap MAPPATH] [interval] [count] [-4 | -6]

DESCRIPTION

       This is top for TCP sessions.

       This summarizes TCP send/receive Kbytes by host, and prints a summary that refreshes, along other system-
       wide metrics.

       This  uses  dynamic  tracing  of  kernel TCP send/receive functions, and will need to be updated to match
       kernel changes.

       The traced TCP functions are usually called at a lower rate than per-packet functions, and therefore have
       lower overhead. The traced data is summarized in-kernel using a BPF map to further  reduce  overhead.  At
       very  high  TCP  event  rates,  the  overhead  may still be measurable. See the OVERHEAD section for more
       details.

       Since this uses BPF, only the root user can use this tool.

REQUIREMENTS

       CONFIG_BPF and bcc.

OPTIONS

       -h     Print USAGE message.

       -C     Don't clear the screen.

       -S     Don't print the system summary line (load averages).

       -p PID Trace this PID only.

       --cgroupmap MAPPATH
              Trace cgroups in this BPF map only (filtered in-kernel).

       --mntnsmap  MAPPATH
              Trace mount namespaces in this BPF map only (filtered in-kernel).

       interval
              Interval between updates, seconds (default 1).

       count  Number of interval summaries (default is many).

       -4     Trace IPv4 family only.

       -6     Trace IPv6 family only.

EXAMPLES

       Summarize TCP throughput by active sessions, 1 second refresh:
              # tcptop

       Don't clear the screen (rolling output), and 5 second summaries:
              # tcptop -C 5

       Trace PID 181 only, and don't clear the screen:
              # tcptop -Cp 181

       Trace a set of cgroups only (see special_filtering.md from bcc sources for more details):
              # tcptop --cgroupmap /sys/fs/bpf/test01

       Trace IPv4 family only:
              # tcptop -4

       Trace IPv6 family only:
              # tcptop -6

FIELDS

       loadavg:
              The contents of /proc/loadavg

       PID    Process ID.

       COMM   Process name.

       LADDR  Local address (IPv4), and TCP port

       RADDR  Remote address (IPv4), and TCP port

       LADDR6 Source address (IPv6), and TCP port

       RADDR6 Destination address (IPv6), and TCP port

       RX_KB  Received Kbytes

       TX_KB  Transmitted Kbytes

OVERHEAD

       This traces all send/receives in TCP, high in the TCP/IP stack  (close  to  the  application)  which  are
       usually  called at a lower rate than per-packet functions, lowering overhead. It also summarizes data in-
       kernel to further reduce overhead. These techniques help, but there may still be measurable  overhead  at
       high  send/receive  rates, eg, ~13% of one CPU at 100k events/sec.  use funccount to count the kprobes in
       the tool to find out this rate, as the overhead is relative to the rate. Some sample  production  servers
       tested  found  total  TCP event rates of 4k to 15k per second, and the CPU overhead at these rates ranged
       from 0.5% to 2.0% of one CPU. If your send/receive rate is low  (eg,  <1000/sec)  then  the  overhead  is
       expected to be negligible; Test in a lab environment first.

SOURCE

       This is from bcc.

              https://github.com/iovisor/bcc

       Also  look  in  the bcc distribution for a companion _examples.txt file containing example usage, output,
       and commentary for this tool.

OS

       Linux

STABILITY

       Unstable - in development.

AUTHOR

       Brendan Gregg

INSPIRATION

       top(1) by William LeFebvre

SEE ALSO

       tcpconnect(8), tcpaccept(8)

USER COMMANDS                                      2020-03-08                                          tcptop(8)