Trying to understand quotas and CPU limits

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Hi everyone,

In a multi-tenancy Kubernetes environment with a CPU quota set per namespace, I’m wondering about the best approach to handle workload fluctuations.Suppose I have two pods:

• The first pod consumes 2000m during the day and 500m at night.
• The second pod consumes 500m during the day and 2000m at night.

To ensure their proper operation, I set a CPU limit of 2000m on each pod. Am I required to request a CPU quota of 4000m for the namespace, even though both pods never use 4000m simultaneously? In other words, does Kubernetes consider the actual CPU usage of the pods, or does it only rely on the sum of the defined limits, regardless of their real-time consumption?

Additionally, if—exceptionally—both pods need to consume 2000m at the same time and they are already deployed, is there any mechanism in Kubernetes that can dynamically limit their total combined consumption to 2000m to stay within the namespace quota?

Thanks in advance for your insights!

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Kubernetes enforces CPU requests and limits separately from namespace quotas. The namespace CPU quota applies to the sum of pod requests, not limits. If your namespace has a quota of 4000m, you must ensure that the combined requests of all running pods do not exceed this, even if actual usage is lower.

To dynamically manage fluctuating workloads within a shared quota, you can:

  1. Set lower requests (e.g., 500m for each pod) so they can scale within the quota.
  2. Use Vertical Pod Autoscaler (VPA) to adjust requests based on usage.
  3. Rely on CPU throttling—if both pods try to use 2000m at once but the quota is lower, Kubernetes will throttle them to stay within limits.
  4. Consider ResourceQuota with LimitRange to enforce balanced resource allocation across pods.

If strict enforcement is needed, Cgroups at the namespace level (via ResourceQuota) ensure total CPU consumption never exceeds the set quota.