Rui Fan created FLINK-40524:
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Summary: LocalInputChannel.getNextBuffer takes the
recoveredBuffers monitor on every buffer even when the channel never needed
recovery
Key: FLINK-40524
URL: https://issues.apache.org/jira/browse/FLINK-40524
Project: Flink
Issue Type: Sub-task
Components: Runtime / Checkpointing
Reporter: Rui Fan
Assignee: Rui Fan
CDR added an unconditional `synchronized (recoveredBuffers)` to the
local-consume hot path [1], but for channels built with `needsRecovery=false`
(all local channels when CDR is off) `inRecovery` is always false and
`recoveredBuffers` always empty, so the block is dead yet still costs a monitor
acquire per buffer. Fix: since `needsRecovery` is final, gate the recovery
block on it so the steady-state path skips the monitor entirely.
[1]
https://github.com/apache/flink/blob/76e774e04ff84ea305714153c5f4790fff98437c/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/LocalInputChannel.java#L566
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