NAME

       gethostlatency.bt   -   Show   latency   for   getaddrinfo/gethostbyname[2]   calls.  Uses
       bpftrace/eBPF.

SYNOPSIS

       gethostlatency.bt

DESCRIPTION

       This traces and prints  when  getaddrinfo(),  gethostbyname(),  and  gethostbyname2()  are
       called,  system  wide, and shows the responsible PID and command name, latency of the call
       (duration) in milliseconds, and the host string.

       This tool can be useful for identifying DNS latency, by identifying which remote host name
       lookups were slow, and by how much.

       This  tool  currently  uses dynamic tracing of user-level functions and registers, and may
       need modifications to match your software and processor architecture.

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

REQUIREMENTS

       CONFIG_BPF and bcc.

EXAMPLES

       Trace host lookups (getaddrinfo/gethostbyname[2]) system wide:
              # gethostlatency.bt

FIELDS

       TIME   Time of the command (HH:MM:SS).

       PID    Process ID of the client performing the call.

       COMM   Process (command) name of the client performing the call.

       LATms  Latency of the call, in milliseconds.

       HOST   Host name string: the target of the lookup.

OVERHEAD

       The rate of lookups should be relatively low, so the overhead is  not  expected  to  be  a
       problem.

SOURCE

       This is from bpftrace.

              https://github.com/iovisor/bpftrace

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

       This is a bpftrace version of the bcc tool of the same name. The bcc tool provides command
       line options.

              https://github.com/iovisor/bcc

OS

       Linux

STABILITY

       Unstable - in development.

AUTHOR

       Brendan Gregg

SEE ALSO

       tcpdump(8)