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Document throughput thresholds in scheduler_perf readme

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Maciej Skoczeń 2024-08-23 12:49:27 +00:00
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test/integration/scheduler_perf/README.md
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@ -129,3 +129,38 @@ The test cases labeled as `short` are executed in pull-kubernetes-integration jo
| ci-kubernetes-integration-master | integration-test |
| pull-kubernetes-integration | integration-test,short |
| ci-benchmark-scheduler-perf | performance |
## Scheduling throughput thresholds
Thresholds are used to capture scheduler performance regressions in a periodic ci-benchmark-scheduler-perf job.
Most test cases have a threshold set for the largest `performance` workloads.
By default, these are defined for the `Average` statistic of the `SchedulingThroughput` metric.
It is possible to use other metric by configuring `thresholdMetricSelector` per test case or workload.
### How to calculate the threshold
The initial values for scheduling throughput thresholds were calculated through an analysis of historical data,
specifically focusing on the minimum, average, and standard deviation values for each workload
(see [#126871](https://github.com/kubernetes/kubernetes/pull/126871)).
Our goal is to set the thresholds somewhat pessimistically to minimize flakiness,
so it's recommended to set the threshold slightly below the observed historical minimum.
Depending on variability of data, the threshold can be lowered more.
Thresholds should be adjusted based on the flakiness level and minima observed in the future.
Remember to set the value for newly added test cases as well,
but after collecting some data on workload characteristics.
### How to determine the failed workload
When the workload's scheduling throughput doesn't exceed the threshold,
the ci-benchmark-scheduler-perf periodic job will fail with an error log such as:
```
--- FAIL: BenchmarkPerfScheduling/SchedulingBasic/5000Nodes_10000Pods
...
scheduler_perf.go:1098: ERROR: op 2: expected SchedulingThroughput Average to be higher: got 256.12, want 270
```
This allows to analyze which workload failed. Make sure that the failure is not an outlier
by checking multiple runs of the job. If the failures are not related to any regression,
but to an incorrect threshold setting, it is reasonable to decrease it.