Clarify system.cpu.utilization metric definition (#2435)

open-telemetry · Mar 28, 2022 · d3dc597 · d3dc597
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diff --git a/specification/metrics/semantic_conventions/README.md b/specification/metrics/semantic_conventions/README.md
@@ -141,7 +141,7 @@ be less than or greater than the real wall time between measurements.
   values. **utilization** for time instruments can be derived automatically
   using metric event timestamps. For example, `system.cpu.utilization` is
   defined as the difference in `system.cpu.time` measurements divided by the
-  elapsed time.
+  elapsed time and number of CPUs.
 
 - **io** - an instrument that measures bidirectional data flow should be
 called `entity.io` and have attributes for direction. For example,

diff --git a/specification/metrics/semantic_conventions/system-metrics.md b/specification/metrics/semantic_conventions/system-metrics.md
@@ -33,7 +33,7 @@ instruments not explicitly defined in the specification.
 | ---------------------- | ----------- | ----- | ---------------------| ---------- | ---------------- | ----------------------------------- |
 | system.cpu.time        |             | s     | Asynchronous Counter | Double     | state            | idle, user, system, interrupt, etc. |
 |                        |             |       |                      |            | cpu              | CPU number [0..n-1]                 |
-| system.cpu.utilization |             | 1     | Asynchronous Gauge   | Double     | state            | idle, user, system, interrupt, etc. |
+| system.cpu.utilization | Difference in system.cpu.time since the last measurement, divided by the elapsed time and number of CPUs | 1     | Asynchronous Gauge   | Double     | state            | idle, user, system, interrupt, etc. |
 |                        |             |       |                      |            | cpu              | CPU number (0..n)                   |
 
 ### `system.memory.` - Memory metrics