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 getaddrinfo(), gethostbyname(), and geth-
ostbyname2() 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)
USER COMMANDS 2018-09-08 gethostlatency.bt(8)
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