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https://issues.apache.org/jira/browse/FLINK-24690?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17440943#comment-17440943
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Piotr Nowojski edited comment on FLINK-24690 at 11/9/21, 9:14 AM:
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I would be in favour of simplifying this so that documentation is not needed,
so always calculating threshold based on the current value - if current buffer
size is 16KB with 50% threshold, a dead zone should be {{{}(8KB, 24KB){}}}
(currently on master the dead zone is {{(8KB, 32KB)}}).
was (Author: pnowojski):
I would be in favour of simplifying this so that documentation is not needed,
so always calculating threshold based on the current value - if current buffer
size is 16KB with 50% threshold, a dead zone should be {{{}(8KB, 24KB){}}}.
> Clarification of buffer size threshold calculation in BufferDebloater
> ----------------------------------------------------------------------
>
> Key: FLINK-24690
> URL: https://issues.apache.org/jira/browse/FLINK-24690
> Project: Flink
> Issue Type: Improvement
> Components: Runtime / Network
> Affects Versions: 1.14.0
> Reporter: Anton Kalashnikov
> Priority: Major
>
> 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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