Info about max_cpu_proxy value

[paolostivanin]

Hello,
I am doing some testing with the parameter cpu_quota_per_share_in_us and I saw that 8 GB and 16 GB apps are behaving the same in terms of cpu load.
Looking at the CC code, I found the following:

cloud_controller_ng/lib/cloud_controller/diego/task_cpu_weight_calculator.rb

Line 5 in d1e08a2

MAX_CPU_PROXY = 8192

this seems to explain the behavior I observed. May I ask what is the rationale behind this value?
And would it be possible to increase it?

Thanks a lot,

Best regards

[cf-gitbot]

We have created an issue in Pivotal Tracker to manage this:

https://www.pivotaltracker.com/story/show/159030303

The labels on this github issue will be updated when the story is started.

[paolostivanin]

I increased the value to 32768, and I was able to solve the issue I was facing.
But, as I don't have the big picture here, I don't know what the side effect of quadrupling that value could be.
Any thoughts?

[cwlbraa]

@paolostivanin good find, it does appear as though the app recipe builder is using that [task] cpu weight calculator. I'm not entirely sure why we cap out cpu quotas like that, but perhaps @emalm could provide some historical context?

[emalm]

I believe the intent was that each app instance would be effectively limited to 1024 CPU shares on the Diego cell, regardless of its memory allocation. That decision was made long before garden-runc-release introduced the opt-in behavior to set a hard CPU quota proportional to that CPU shares allocation.

In any case, we're planning on moving forward with the proposal @julz put forth a few months ago at https://docs.google.com/document/d/16TvBsZSInjy7zoboSQWRJo30lmxr07tvd40_GzpfD3I/edit, with the Garden team having some of this work in flight already.

Best,
Eric

[selzoc]

Thanks for the info @emalm !!

Closing this issue as there is no cloud_controller action to take until the Garden/Diego work is done.