Anton Kalashnikov created FLINK-24690:
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Summary: Clarification of buffer size threshold calculation in
BufferDebloater
Key: FLINK-24690
URL: https://issues.apache.org/jira/browse/FLINK-24690
Project: Flink
Issue Type: Bug
Components: Runtime / Network
Affects Versions: 1.14.0
Reporter: Anton Kalashnikov
It looks like that the variable `skipUpdate` in
BufferDebloater#recalculateBufferSize is calculated in a not obvious way.
For example if
`taskmanager.network.memory.buffer-debloat.threshold-percentages` is set to
50(means 50%) then it will be something like:
* 32000 -> 16000(possible)
* 32000 -> 17000(not possible)
* 16000 -> 24000(not possible) - but 16000 + 50% = 24000
* 16000 -> 32000(only this possible)
This happens because the algorithm takes into account only the largest value.
So in example of `16000 -> 24000` it would calculate 50% of 24000 so only
transit from 12000 -> 24000 possible.
In general, this approach is not so bad especially on small values (instead of
256 ->374, the minimum possible transit is 256 -> 512). But we should clarify
it somewhere with test or javadoc or both. Also, we can discuss changing this
algorithm to a more natural implementation.
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