Merge pull request #132 from DataDog/kowalski/python_spiky-improve-expected-profile

[python_spiky] Improve expected profile

Co-authored-by: KowalskiThomas <thomas.kowalski@datadoghq.com>
Co-authored-by: taegyun.kim <taegyun.kim@datadoghq.com>

Author: 3 people

scenarios/python_spiky_3.11/README.md

@@ -9,4 +9,20 @@ Two threads run concurrently for the same duration:
 ## Expected behavior
 
 - **wall-time**: both threads contribute ~50% each, since both run for the same duration
-- **cpu-time**: only `cpu_work` appears (~90%+), since sleeping does not consume CPU
+- **cpu-time**: only `cpu_work` appears (~99%+), since sleeping does not consume CPU
+
+## CPU usage over time
+
+Execution alternates CPU spikes (busy-looping on `math.factorial`, ~100% CPU)
+with sleep periods (~0% CPU). Spike/sleep lengths are random, but each half of
+the run sums to `EXECUTION_TIME_SEC / 2`, so the mean CPU usage is exactly 50%.
+
+```text
+CPU
+100% ┤ ┌──┐   ┌─┐  ┌──┐  ┌─┐   ┌──┐  ┌─┐  ┌──┐
+     │ │  │   │ │  │  │  │ │   │  │  │ │  │  │
+ 50% ┼─┼──┼───┼─┼──┼──┼──┼─┼───┼──┼──┼─┼──┼──┼──  mean = 50%
+     │ │  │   │ │  │  │  │ │   │  │  │ │  │  │
+  0% ┴─┘  └───┘ └──┘  └──┘ └───┘  └──┘ └──┘  └──▶ time
+       cpu  sleep cpu sleep ...  (each half sums to 50%)
+```

scenarios/python_spiky_3.11/expected_profile.json

@@ -21,8 +21,13 @@
       "stack-content": [
         {
           "regular_expression": ".*cpu_spike",
-          "percent": 90,
-          "error_margin": 10
+          "percent": 99,
+          "error_margin": 5
+        },
+        {
+          "regular_expression": ".*sleep_period",
+          "percent": 0,
+          "error_margin": 5
         }
       ]
     }