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Demonstrations of oomkill, the Linux bpftrace/eBPF version.


oomkill is a simple program that traces the Linux out-of-memory (OOM) killer,
and shows basic details on one line per OOM kill:

# ./oomkill.bt
Tracing oom_kill_process()... Ctrl-C to end.
21:03:39 Triggered by PID 3297 ("ntpd"), OOM kill of PID 22516 ("perl"), 3850642 pages, loadavg: 0.99 0.39 0.30 3/282 22724
21:03:48 Triggered by PID 22517 ("perl"), OOM kill of PID 22517 ("perl"), 3850642 pages, loadavg: 0.99 0.41 0.30 2/282 22932

The first line shows that PID 22516, with process name "perl", was OOM killed
when it reached 3850642 pages (usually 4 Kbytes per page). This OOM kill
happened to be triggered by PID 3297, process name "ntpd", doing some memory
allocation.

The system log (dmesg) shows pages of details and system context about an OOM
kill. What it currently lacks, however, is context on how the system had been
changing over time. I've seen OOM kills where I wanted to know if the system
was at steady state at the time, or if there had been a recent increase in
workload that triggered the OOM event. oomkill provides some context: at the
end of the line is the load average information from /proc/loadavg. For both
of the oomkills here, we can see that the system was getting busier at the
time (a higher 1 minute "average" of 0.99, compared to the 15 minute "average"
of 0.30).

oomkill can also be the basis of other tools and customizations. For example,
you can edit it to include other task_struct details from the target PID at
the time of the OOM kill, or to run other commands from the shell.

There is another version of this tool in bcc: https://github.com/iovisor/bcc