Re: OOM: Better, but still there on

On Sat, Dec 17, 2016 at 11:44:45PM +0900, Tetsuo Handa wrote:

On 2016/12/17 21:59, Nils Holland wrote:

quoted

On Sat, Dec 17, 2016 at 01:02:03AM +0100, Michal Hocko wrote:

quoted

mount -t tracefs none /debug/trace
echo 1 > /debug/trace/events/vmscan/enable
cat /debug/trace/trace_pipe > trace.log

should help
[...]

No problem! I enabled writing the trace data to a file and then tried
to trigger another OOM situation. That worked, this time without a
complete kernel panic, but with only my processes being killed and the
system becoming unresponsive.
[...]

Under OOM situation, writing to a file on disk unlikely works. Maybe
logging via network ( "cat /debug/trace/trace_pipe > /dev/udp/$ip/$port"
if your are using bash) works better. (I wish we can do it from kernel
so that /bin/cat is not disturbed by delays due to page fault.)

If you can configure netconsole for logging OOM killer messages and
UDP socket for logging trace_pipe messages, udplogger at
https://osdn.net/projects/akari/scm/svn/tree/head/branches/udplogger/
might fit for logging both output with timestamp into a single file.

Thanks for the hint, sounds very sane! I'll try to go that route for
the next log / trace I produce. Of course, if Michal says that the
trace file I've already posted, and which has been logged to file, is
useless and would have been better if I had instead logged to a
different machine via the network, I could also repeat the current
experiment and produce a new file at any time. :-)

Greetings
Nils