Default cgroup CPU share


John Wong
 

I am reading
https://docs.cloudfoundry.org/concepts/architecture/warden.html#cpu and it
said:

If B is idle, A may receive up to all the CPU. Shares per cgroup range
from 2 to 1024, with 1024 the default. Both Diego apps and DEA apps scale
the number of allocated shares linearly with the amount of memory, with an
app instance requesting 8G of memory getting the upper limit of 1024
shares. Diego also guarantees a minimum of 10 shares per app instance.

So 1024 is the default share every app get by default?

Say I start with an empty DEA.


APP #1: 1G shared = 1024?

APP #2 added. 1G shared =? what happen to APP #1?

APP #2 added: 512MB shared =? What happened to APP #1 & APP 2?

APP #3 added: 8GB, now what happened?


I am all assuming their usage is nearly idle. What is the total number of
share for a N-core DEA? Also are the shares dynamic? In the mean time I
will try to understand how CPU usage is shared in cgroup from other
resource.


Thanks.


John

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