[Starlingx-discuss] Agenda: Weekly Containerization Meeting Monday April 29

[Victor Rodriguez]

On Mon, Apr 29, 2019 at 10:29 PM Rowsell, Brent
<Brent.Rowsell at windriver.com> wrote:
>
> Victor,
>
> See inline
>
> Brent
>
> -----Original Message-----
> From: Victor Rodriguez [mailto:vm.rod25 at gmail.com]
> Sent: Monday, April 29, 2019 9:43 AM
> To: Miller, Frank <Frank.Miller at windriver.com>
> Cc: starlingx-discuss at lists.starlingx.io
> Subject: Re: [Starlingx-discuss] Agenda: Weekly Containerization Meeting Monday April 29
>
> Hi Frank
>
> I am in charge of the track of performance and footprint of the STX systems
>
> Due to the fact that this bug was a footprint issue I was wondering if should discuss on the meeting on what stages and part of the STX do you want me to track the memory footprint
>
> Also, I have a question regarding the chance to set up -m to each docker image so we can limit the amount of memory of each one. One of the experiments we did las Friday debugging the issue was that if we set -m and the system has SWAP it will take memory from there and keep running since we in STX do not have swap the containers fails from starvation.
> [BR] Enabling SWAP, in general, is not an option for performance reasons. On top of that it will not work with k8s.
>

I agree after reading the full thread[0] that Bin share and reading
docker documentation that yes swap is not working on k8, thanks for
the clarification it helps me a lot.

Now related to the performance.

I do understand that if the scheduler sends a pod to a machine it
should never use swap at all. but here my question ( as Linux
performance eng ) could be. Why ? and what benchmarks prove that ?. As
far as I know, please correct me if I am wrong,  It’s normal and can
be a good thing for Linux systems to use some swap, even if there is
still available RAM. The Linux Kernel will move memory pages which are
hardly ever used into swap space to ensure that even more cachable
space is made available in-memory for more frequently used memory
pages (a page is a piece of memory). Swap usage becomes a performance
problem when the Kernel is pressured to continuously move memory pages
in and out of memory and swap space. ( is this the corner case that we
are preventing not to use the swap ) . Another advantage is that swap
gives admins time to react to low memory issues. We will often notice
the server acting slowly and upon login will notice heavy swapping.
Without swap running out of memory can create much more sudden and
severe chain reactions.

Obed/Dean, do you know of any benchmark or use case that proves this ?
just wondering

[0] https://github.com/kubernetes/kubernetes/issues/53533

> Regards
>
> Victor R
>
> On Mon, Apr 29, 2019 at 8:34 AM Miller, Frank <Frank.Miller at windriver.com> wrote:
> >
> > We will be holding a meeting today.  Planned agenda is below – please add to the etherpad agenda if you have any additional topics to discuss:
> >
> >
> >
> > Etherpad: https://etherpad.openstack.org/p/stx-containerization
> >
> >
> >
> > Agenda:
> >
> > 1. Sanity status/issue discussion:
> >
> >     - All in one systems, bare metal
> >
> >     - Multi node systems
> >
> >     - Virtual systems
> >
> >
> >
> > 2. Test team status & top issues
> >
> >
> >
> > 3. Feature Topics:
> >
> >     - Overall status
> >
> >     - Technical discussion on any outstanding features
> >
> >
> >
> > 4. Open topics
> >
> >     - no meeting Monday May 6th
> >
> >     - other items?
> >
> >
> >
> >
> >
> > ------
> >
> > Frank
> >
> >
> >
> > _______________________________________________
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> > Starlingx-discuss at lists.starlingx.io
> > http://lists.starlingx.io/cgi-bin/mailman/listinfo/starlingx-discuss
>
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