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https://issues.apache.org/jira/browse/HBASE-27458?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Xiaolin Ha resolved HBASE-27458.
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Resolution: Fixed
Merged to master and branch-2+, thanks [~frostruan] for contributing, and
thanks [~zhangduo] for reviewing.
> 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
> Priority: Minor
> Fix For: 2.6.0, 3.0.0-alpha-4, 2.4.17, 2.5.4
>
> 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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