Why is cpu usage metric more than cpu usage percentage?

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Why is cpu usage metric more than cpu usage percentage?

Dylan 20

For the record, I tried asking this question here but for some reason it 404s so I'm reposting a summary of it.

I have a container app allocated 1 core and 2 GB of memory and set to 2 replicas.

When I view the cpu usage avg metric and add a filter to view only one replica, I see 0.45 cores. Because the app is allocated only 1 core, this makes me think the percentage is 45%. However when I swap the metric to see cpu usage percentage, it shows me just 33%.

What's the cause for this difference?

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Answer 1

Thanks for posting your question in the Microsoft Q&A forum.

The difference between CPU usage and CPU usage percentage in Azure Container Apps is due to how these metrics are calculated and reported.

CPU Usage is reported in millicores, where 1000 millicores equal 1 full CPU core. When you see a CPU usage of 0.45 cores, this actually represents 450 millicores, which is indeed 45% of a single core.

CPU Usage Percentage, on the other hand, is reported as a percentage of the CPU limit used. This metric is calculated differently and may take into account factors such as the container's CPU limit and the actual physical resources available.

The discrepancy you're observing (45% vs 33%) could be due to several factors:

Measurement intervals: The two metrics might be calculated over different time periods.
Resource limits: The percentage might be calculated based on the total available resources across all replicas, not just the single core allocated to each replica.
Preview status: As the CPU Usage Percentage metric is in preview, it may still have some inconsistencies or be calculated differently from the CPU Usage metric.

Please don't forget to close up the thread here by upvoting and accept it as an answer if it is helpful

Shireesha Eeraboina 3,435 Reputation points Microsoft External Staff Moderator

2025-02-10T05:08:06.6966667+00:00

Hi @Dylan,

Just checking in to see if the above answer provided by @hossein jalilian helped.

If this answers your query, do click Accept Answer and Yes for was this answer helpful. And, if you have any further query do let us know.
Dylan 20 Reputation points

2025-02-10T17:05:05.07+00:00

@Shireesha Eeraboina Yes it helped.

"Resource limits: The percentage might be calculated based on the total available resources across all replicas, not just the single core allocated to each replica."

I expected that using the filter so only one replica is visible would prevent that from happening. It's surprising if that's not the case.

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Why is cpu usage metric more than cpu usage percentage?

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