Manual: gethostlatency.bt

gethostlatency.bt(8)				   System Manager's Manual				gethostlatency.bt(8)

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

SYNOPSIS
       gethostlatency.bt

DESCRIPTION
       This  traces and prints when gethostbyaddr(), 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/bpftrace/bpftrace

       Also  look in the bpftrace distribution for a companion _examples.txt file containing example usage, output, and com‐
       mentary 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), gethostbyname(3), getaddrinfo(3)

USER COMMANDS						 2018-09-08					gethostlatency.bt(8)