Open Stack

And who said openstack wasn't growing? ;)

I think reducing API workers is a nice quick way to bring back some
stability.

I have spent a bunch of time digging into the OOM killer events and haven't
yet figured out why they are being triggered. There is significant swap
space remaining in all of the cases I have seen so it's likely some memory
locking issue or kernel allocations blocking swap. Until we can figure out
the cause, we effectively have no usable swap space on the test instances
so we are limited to 8GB.

On Feb 1, 2017 17:27, "Armando M." <armamig at gmail.com> wrote:

> Hi,
>
> [TL;DR]: OpenStack services have steadily increased their memory
> footprints. We need a concerted way to address the oom-kills experienced in
> the openstack gate, as we may have reached a ceiling.
>
> Now the longer version:
> --------------------------------
>
> We have been experiencing some instability in the gate lately due to a
> number of reasons. When everything adds up, this means it's rather
> difficult to merge anything and knowing we're in feature freeze, that adds
> to stress. One culprit was identified to be [1].
>
> We initially tried to increase the swappiness, but that didn't seem to
> help. Then we have looked at the resident memory in use. When going back
> over the past three releases we have noticed that the aggregated memory
> footprint of some openstack projects has grown steadily. We have the
> following:
>
>    - Mitaka
>       - neutron: 1.40GB
>       - nova: 1.70GB
>       - swift: 640MB
>       - cinder: 730MB
>       - keystone: 760MB
>       - horizon: 17MB
>       - glance: 538MB
>    - Newton
>    - neutron: 1.59GB (+13%)
>       - nova: 1.67GB (-1%)
>       - swift: 779MB (+21%)
>       - cinder: 878MB (+20%)
>       - keystone: 919MB (+20%)
>       - horizon: 21MB (+23%)
>       - glance: 721MB (+34%)
>    - Ocata
>       - neutron: 1.75GB (+10%)
>       - nova: 1.95GB (%16%)
>       - swift: 703MB (-9%)
>       - cinder: 920MB (4%)
>       - keystone: 903MB (-1%)
>       - horizon: 25MB (+20%)
>       - glance: 740MB (+2%)
>
> Numbers are approximated and I only took a couple of samples, but in a
> nutshell, the majority of the services have seen double digit growth over
> the past two cycles in terms of the amount or RSS memory they use.
>
> Since [1] is observed only since ocata [2], I imagine that's pretty
> reasonable to assume that memory increase might as well be a determining
> factor to the oom-kills we see in the gate.
>
> Profiling and surgically reducing the memory used by each component in
> each service is a lengthy process, but I'd rather see some gate relief
> right away. Reducing the number of API workers helps bring the RSS memory
> down back to mitaka levels:
>
>    - neutron: 1.54GB
>    - nova: 1.24GB
>    - swift: 694MB
>    - cinder: 778MB
>    - keystone: 891MB
>    - horizon: 24MB
>    - glance: 490MB
>
> However, it may have other side effects, like longer execution times, or
> increase of timeouts.
>
> Where do we go from here? I am not particularly fond of stop-gap [4], but
> it is the one fix that most widely address the memory increase we have
> experienced across the board.
>
> Thanks,
> Armando
>
> [1] https://bugs.launchpad.net/neutron/+bug/1656386
> [2] http://logstash.openstack.org/#/dashboard/file/logstash.
> json?query=message:%5C%22oom-killer%5C%22%20AND%20tags:syslog
> [3] http://logs.openstack.org/21/427921/1/check/gate-
> tempest-dsvm-neutron-full-ubuntu-xenial/82084c2/
> [4] https://review.openstack.org/#/c/427921
>
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