Hi team, I am writing to propose an urgent revert of PR #23611
- https://github.com/apache/pulsar/pull/23611 *Reason for Revert:* This PR has introduced a significant performance regression in the Pulsar broker. The attached flame graph visually demonstrates increased CPU utilization and time spent in the code paths related to DelayedDeliveryTracker and stream operations. While the intention was to optimize memory usage, the current implementation appears to have an adverse effect on CPU performance, leading to overall degraded broker throughput and increased latency. *Impact:* This regression is impacting the stability and performance of our Pulsar clusters, especially when you have large-scale delayed messages. Reverting the change will allow us to restore the previous performance characteristics while we investigate a more robust and performant solution for DelayedDeliveryTracker memory optimization. *Proposed Action:* I propose to revert PR #23611 as soon as possible to reduce the risk to other users, and we can then collectively work on a more thoroughly tested and performant approach to optimize the DelayedDeliveryTracker memory. Please let me know your thoughts, and if there are any immediate concerns with this proposed revert. Regards, Penghui
