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Apply minimumCPUShare to both task and container CPU shares #3156

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merged 1 commit into from Mar 28, 2022

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yinyic
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@yinyic yinyic commented Mar 25, 2022

Summary

taskCPUShares is used when creating task cgroup spec. We have a minimumCPUShare (equals 2) but it currently applies to container CPU shares only (more context under cpu section of the API doc).

This value should be applicable to task CPU share as well for the following reasons:

  1. We sum up container CPU shares and add that to task CPU share. Because a task must have at least one container, and the container CPU share will be >= 2, then task CPU share should naturally be >= 2.
  2. Cgroupv2 requires CPU share to be >= 2 due to this conversion from CPU shares to CPU weight. This is where the conversion happens in the containerd/cgroups library that we use.

Implementation details

When add each container CPU share to task CPU share, use minimumCPUShare if container CPU share is less than that.

Testing

New tests cover the changes: unit test

Additional manual testing: applied this commit to the cgroupv2 branch, started Agent on an AL2022 instance where cgroupv2 is enabled, and verified that task with container cpu share equals 1 can be started.

Description for the changelog

Apply minimumCPUShare to both task and container CPU shares

Licensing

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

@@ -148,18 +148,13 @@ func (task *Task) buildImplicitLinuxCPUSpec() specs.LinuxCPU {
// aggregate container CPU shares when present
var taskCPUShares uint64
for _, container := range task.Containers {
if container.CPU > 0 {
if container.CPU < minimumCPUShare {
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@singholt singholt Mar 25, 2022

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if a task has 2 containers with no container-level CPU defined (container.CPU = 0) and no task-level CPU defined (task.CPU). then agent would set taskCPUShares to 4 but we want it to be 2?

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Yes - I believe that should be the correct behavior because we later on bump container CPU shares to 2, if the value specified in task def is smaller (or unspecified). So if you have 2 containers they will both have CPUShares=2 when passed to docker, which makes sense for the task CPU share to be 4 in that case.

@yinyic yinyic merged commit d5041e2 into aws:dev Mar 28, 2022
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4 participants