Viraj Jasani created HBASE-26018:
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Summary: Perf improvement in L1 cache
Key: HBASE-26018
URL: https://issues.apache.org/jira/browse/HBASE-26018
Project: HBase
Issue Type: Improvement
Affects Versions: 2.4.4, 2.3.5, 3.0.0-alpha-1
Reporter: Viraj Jasani
Assignee: Viraj Jasani
Fix For: 3.0.0-alpha-1, 2.5.0, 2.3.6, 2.4.5
After HBASE-25698 is in, all L1 caching strategies perform buffer.retain() in
order to maintain refCount atomically while retrieving cached blocks
(CHM#computeIfPresent). Retaining refCount is coming up bit expensive in terms
of performance issues. Using computeIfPresent API, CHM uses coarse grained
segment locking and even if our computation is not so complex (we just call
block retain API), it will block other update APIs for the key.
computeIfPresent keeps showing up on flame graphs as well (attached one of
them). Specifically when we see aggressive cache hits for meta blocks (with
major blocks in cache), we would want to get away from coarse grained locking.
One of the suggestions came up while reviewing PR#3215 is to treat cache read
API as optimistic read and deal with block retain based refCount issues by
catching the respective Exception and let it treat as cache miss. This should
allow us to go ahead with lockless get API.
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