Show memory usage independent of the used memory limit

[c0d1ngm0nk3y]

Current behavior

Currently, the shown memory metric is influenced by the memory limit which leads to confusing behaviors.

App used to reproduce: https://github.com/cloudfoundry/cf-acceptance-tests/tree/develop/assets/binary

cf push 200 -b binary_buildpack --random-route -m 200M
cf app 200
...
memory usage:   200M
     state     since                  cpu    memory          disk         logging             cpu entitlement   details
#0   running   2025-10-02T15:03:49Z   1.6%   15.5M of 200M   6.4M of 1G   0B/s of unlimited   40.9%

cf push 20 -b binary_buildpack --random-route -m 20M
cf app 20
...
memory usage:   20M
     state     since                  cpu    memory        disk         logging             cpu entitlement   details
#0   running   2025-10-02T15:08:14Z   1.6%   4.9M of 20M   6.4M of 1G   0B/s of unlimited   79.7%

cf push 5 -b binary_buildpack --random-route -m 5M
cf app 5
...
memory usage:   5M
     state     since                  cpu    memory       disk         logging             cpu entitlement   details
#0   running   2025-10-02T15:10:40Z   1.7%   1.5M of 5M   6.4M of 1G   0B/s of unlimited   87.8%

cf push 2 -b binary_buildpack --random-route -m 2M
cf app 2
...
memory usage:   2M
     state     since                  cpu    memory         disk         logging             cpu entitlement   details
#0   running   2025-10-02T15:11:36Z   1.5%   660.7K of 2M   6.4M of 1G   0B/s of unlimited   78.2%

cf push 1 -b binary_buildpack --random-route -m 1M
cf app 1
...
memory usage:   1M
     state     since                  cpu    memory         disk         logging             cpu entitlement   details
#0   running   2025-10-02T15:12:49Z   1.7%   328.7K of 1M   6.4M of 1G   0B/s of unlimited   88.7%

Due to a bug in the cli, this cannot be continued, but I think the problem is clear. How much memory does the app consume ~15MB or ~300KB?

The problem is caused by a sidecar being added with a limit of 64MB.

Desired behavior

It would be great to see the memory the app actually consumes.

Affected Version

2.121.0

[chombium]

Just a small clarification: the 64MB sidecar is Envoy. The memory used is controlled by the containers.proxy.additional_memory_allocation_mb which we've set to 64MB in our foundations

[mariash]

Hi @chombium, I reproduced this issue. I checked the processes and their actual memory usage on Diego cell. They were both around 18Mb. For some reason, the reported memory is scaled to always be under the memory limit. I found this commit from 2017, but I can't find any explanations why was this done. But it seems like it was done on purpose - cloudfoundry/executor@5bebc6a#diff-9a860e23c6233b6e4e66aac392805e66f0201827ef2df9f5010df734419d9dfc

[chombium]

Hi @mariash, I know that this is a really old change and I guess we have many people are relying on this behavior. I guess it will be hard to change this without breaking anything. I suggest that for now we document how this works, so that everyone knows what to expect.

[c0d1ngm0nk3y]

Hi. Any updates on this one. It is not really a problem, but looks really strange.

For some reason, the reported memory is scaled to always be under the memory limit. I found this commit from 2017, but I can't find any explanations why was this done. But it seems like it was done on purpose -

I guess with the envoy sharing the same cgroup as the application, there was no option but to increase the limit. I would only like to understand 2 things

a) Why was the envoy put in the same cgroup?
b) Why was this done in such a intransparent way? The limit could have been increased by the envoy limit.