Github user lvfangmin commented on the issue:
https://github.com/apache/zookeeper/pull/590
Based on internal benchmark, this may save more than 95% memory usage on
concentrate watches scenario. I'm working on adding some micro benchmark.
In the original Jira, @phunt also added some basic test, which could show
you some ideas about how much memory it's going to save.
The current HashMap based watch manager uses lots of memory due to the
overhead of storing each entry (32 Bytes for each entry), the object reference
and the duplicated path strings.
Use BitSet without revert index could reduce those overhead and make it
more memory efficient.
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