Rajesh Balamohan created HDDS-2324:
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Summary: Enhance locking mechanism in OzoneMangaer
Key: HDDS-2324
URL: https://issues.apache.org/jira/browse/HDDS-2324
Project: Hadoop Distributed Data Store
Issue Type: Bug
Components: Ozone Manager
Reporter: Rajesh Balamohan
OM has reentrant RW lock. With 100% read or 100% write benchmarks, it works out
reasonably fine. There is already a ticket to optimize the write codepath (as
it incurs reading from DB for key checks).
However, when small amount of write workload (e.g 3-5 threads) is added to the
running read benchmark, throughput suffers significantly. This is due to the
fact that the reader threads would get blocked often. I have observed around
10x slower throughput (i.e 100% read benchmark was running at 12,000 TPS and
with couple of writer threads added to it, it goes down to 1200-1800 TPS).
1. Instead of single write lock, one option could be good to scale out the
write lock depending on the number of cores available in the system and acquire
relevant lock by hashing the key.
2. Another option is to explore if we can make use of StampedLocks of JDK 8.x,
which scales well when multiple readers and writers are there. But it is not a
reentrant lock. So need to explore whether it can be an option or not.
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