We are experiencing occasional hangs with ubuntu 16.04 LTS (kernel 4.4.0-34-generic) and we wonder if somebody has some clues how to get to bottom of this.
The log looks like this:
Aug 24 10:02:04 Ubuntu-1404-trusty-64-minimal kernel: [ 2046.519099] perf interrupt took too long (2505 > 2500), lowering kernel.perf_event_max_sample_rate to 50000
Aug 24 10:03:19 Ubuntu-1404-trusty-64-minimal systemd[1]: Started Session 43 of user ubuntu.
Aug 24 10:06:21 Ubuntu-1404-trusty-64-minimal systemd[1]: Started Session 44 of user ubuntu.
Aug 24 10:06:22 Ubuntu-1404-trusty-64-minimal systemd[1]: Started Session 45 of user ubuntu.
Aug 24 10:08:14 Ubuntu-1404-trusty-64-minimal systemd[1]: Started Session 46 of user ubuntu.
Aug 24 10:17:01 Ubuntu-1404-trusty-64-minimal CRON[150011]: (root) CMD ( cd / && run-parts --report /etc/cron.hourly)
Aug 24 10:20:11 Ubuntu-1404-trusty-64-minimal systemd[1]: Started Session 48 of user ubuntu.
Aug 24 10:26:28 Ubuntu-1404-trusty-64-minimal systemd[1]: Started Session 49 of user ubuntu.
^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@
The problem only happens with machines with SSD disk attached.
The memory and disk is checked and 100% ok.
The problem happens only on ubuntu 16.04.
Ubuntu 14.04 LTS does not run into this problem.
So this is definitely some software bug. The questions here is: What actions one can take to troubleshoot this? Which logs / debugs we should enable to get to the bottom of this?