smerkerg commented on issue #1407: HBASE-24099 Use a fair ReentrantReadWriteLock for region close lock URL: https://github.com/apache/hbase/pull/1407#issuecomment-610118706 I am not an expert on the locks, but looking through the code I only found two cases where the `writeLock` is taken: `startBulkRegionOperation` and `doClose`. I'm guessing very few of those operations happen during the performance tests. So, as a result, I'd expect to not see too much overhead in enforcing the fairness. Most locks should be read-only, so contention should be minimal. If that's true, then it could explain that a lot of the ~10% changes are just normal variance. Put another way, there should be absolutely no reason why some read cases get faster with a fair lock pattern... right? So that seems to suggest a variance level around ~10%. All of this makes me feel pretty good about the performance results not showing a regression.
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