[Perf] Invalid intermediate results when using multiple processes

[mikeharder]

When testing the multi-process support in #22997, I sometimes see invalid intermediate results. The last line reports -27 operations which is obviously wrong. But the final results (72 operations in 5.09s) are correct.

> systemperf SleepTest -w 0 -d 5 --parallel 4 --instance-growth-factor 0.5

=== Options ===
Namespace(test='SleepTest')
Namespace(parallel=4, processes=12, duration=5, warmup=0, no_cleanup=False, sync=False, profile=False, test_proxies=None, insecure=False, initial_delay_ms=1000, instance_growth_factor=0.5, iteration_growth_factor=1)

=== Tests ===
Current         Total           Average
11              11              13.25
1               12              14.25
14              26              14.15
15              41              14.22
14              55              14.21
-27             28              5.78

Completed 72 operations in a weighted-average of 5.09s (14.15 ops/s, 0.071 s/op)

[github-actions]

Hi @mikeharder, we deeply appreciate your input into this project. Regrettably, this issue has remained inactive for over 2 years, leading us to the decision to close it. We've implemented this policy to maintain the relevance of our issue queue and facilitate easier navigation for new contributors. If you still believe this topic requires attention, please feel free to create a new issue, referencing this one. Thank you for your understanding and ongoing support.