pnowojski commented on issue #8455: [FLINK-12284][Network,Metrics]Fix the incorrect inputBufferUsage metric in credit-based network mode URL: https://github.com/apache/flink/pull/8455#issuecomment-495661903 > The current inputBufferUsage is only reflecting the usage of floating buffers, and it could give an indicator whether the setting of floating-buffers-per-gate is enough for performance tuning. I agree, there is a value of the current semantic. I would even build upon that. If you want to detect bottleneck, current semantic of tracking just floating buffers is perfect for that. If current operator (reading from this input) is causing a bottleneck it well can be that only a single one input channel is back-pressured. At the moment we could detect this situation with "all floating buffers are exhausted/used". > We could always assume if the exclusive buffers are enough for one channel, it will not request floating buffers. In other words, if we see the floating buffers are used, that means the exclusive buffers should also be used. This is not true for even slight data skew. I think that there is a value of tracking separately floating and exclusive buffers. Maybe we should make `inPoolUsage` track `floating + exclusive` buffers (it would make it consistent with non credit based mode), while we could add `inFloatingPoolUsage` metric with current semantic? What do you think?
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