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]

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).

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

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)