Discrepancy between `cf apps` memory usage and cgroup's memory.usage_in_bytes in CF 2.13.0


Daniel Jones
 

Hi all,

Whilst investigating the Java Buildpack out-of-memory issues David
Head-Rapson mailed about the other day, we discovered a discrepancy between
the memory usage stat provided by `cf app` and the value stored in the
corresponding cgroup's `memory.usage_in_bytes` file. The latter seems to be
bumping right along the maximum allowed.


- We did a `cf app`, and got a memory stat of 847.6MiB of 896MiB.
- We got the appId from CF_TRACE, `bosh ssh`'d onto the right DEA
- We then did `cat
tmp/warden/cgroup/memory/instance-id/memory.usage_in_bytes` and got
939,515,904, which equates to 895.99ish MiB.

Does anyone know why the latter is so high, and why it would differ from
what the DEA reports back to the Cloud Controller? There's clearly a gap in
our understanding somewhere, so any help would be much appreciated.

Many thanks,

Daniel Jones
EngineerBetter.com

Join cf-dev@lists.cloudfoundry.org to automatically receive all group messages.