Module metrics 

Defines the metrics system for memory devices.

Metrics format

The metrics are flushed in JSON when requested by vmm::logger::metrics::METRICS.write().

JSON example with metrics:

 "memory_hotplug": {
    "activate_fails": "SharedIncMetric",
    "queue_event_fails": "SharedIncMetric",
    "queue_event_count": "SharedIncMetric",
    ...
 }
}

Each memory field in the example above is a serializable VirtioMemDeviceMetrics structure collecting metrics such as activate_fails, queue_event_fails etc. for the memoty hotplug device. Since Firecrakcer only supports one virtio-mem device, there is no per device metrics and memory_hotplug represents the aggregate entropy metrics.

Functions

flush_metrics

Called by METRICS.flush(), this function facilitates serialization of virtio-mem device metrics.