Commits on Sep 20, 2024

1. [PROF-10422] Fix flaky GVL profiling integration spec …

   **What does this PR do?**
   
   This PR fixes a flaky specs seen in
   https://app.circleci.com/pipelines/github/DataDog/dd-trace-rb/16487/workflows/df69cfde-1fd5-40dc-bff6-ac8a9d0bc713/jobs/593534 :
   
   ```
     1) Datadog::Profiling::Collectors::CpuAndWallTimeWorker#start when main thread is sleeping but a background thread is working when GVL profiling is enabled records Waiting for GVL samples
        Failure/Error: expect(waiting_for_gvl_time).to be_within(5).percent_of(total_time)
          expected 402832467 to be within 5% of 492191168
   ```
   
   I was able to reproduce this failure on my local machine in around 1 in
   20 runs.
   
   This flakiness is caused by the profiler starting after a Waiting for
   GVL already started, and thus the profiler does not see it and still
   categorizes that period as "unknown"; thus our tight assertion is blown.
   
   It's not a concidence that the difference between 492191168 and
   402832467 is within ~100ms: that's the scheduler latency caused
   by the background thread that's burning CPU.
   
   To fix this issue, we subtract the duration of this initial period
   from the `total_time`: this is the period we care for.
   
   To avoid us accidentally passing this test by having no Waiting for GVL,
   I've added an additional assertion for a sane `total_value`.
   
   **Motivation:**
   
   Make sure the profiler has zero flaky specs.
   
   **Additional Notes:**
   
   N/A
   
   **How to test the change?**
   
   Validate that CI is green and that the flaky test does not show up
   again.

   

   ivoanjo committed Sep 20, 2024
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