ruanhui created HBASE-27458:
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Summary: Use ReadWriteLock for region scanner readpoint map
Key: HBASE-27458
URL: https://issues.apache.org/jira/browse/HBASE-27458
Project: HBase
Issue Type: Improvement
Components: Scanners
Affects Versions: 3.0.0-alpha-3
Reporter: ruanhui
Assignee: ruanhui
Fix For: 3.0.0-alpha-4
Attachments: jstack-2.png
Currently we manage the concurrency between the RegionScanner and
getSmallestReadPoint by synchronizing on the scannerReadPoints object. In our
production, we find that many read threads are blocked by this when we have a
heavy read load.
we need to get smallest read point when
a. flush a memstore
b. compact memstore/storefile
c. do delta operation like increment/append
Usually the frequency of these operations is much less than read requests.
It's a little expensive to use an exclusive lock here because for region
scanners, what it need to do is just calcaulating readpoint and putting the
readpoint in the scanner readpoint map, which is thread-safe. Multiple read
threads can do this in parallel without synchronization.
Based on the above consideration, maybe we can replace the synchronized lock
with readwrite lock. It will help improve the read performance if the
bottleneck is on the synchronization here.
!jstack.png!
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