How does the Amazon CloudWatch work?

Suppose I have an EC2 instance, which I understood is a VM instance. So if I enable CloudWatch for this EC2 instance, should this monitoring capabilitiy offered by CloudWatch added into my EC2 instance, or it is just running in the hypervisor like XEN?

Thanks.

Solution

It is monitored at the hypervisor layer. Aamazon generally will not look into the instance at VM layer so they can't monitor some feature such as memroy usage at the VM.