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https://issues.apache.org/jira/browse/HADOOP-2139?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12540617
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Jim Kellerman commented on HADOOP-2139:
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Strategy:
Associate memcache with HStore instead of HRegion - reduces contention between
most other ops and scanners.
If a scanner is open on a memcache, and an update arrives, push the memcache on
a stack and create a new memcache for the update. This is unlikely to cause the
generation of a lot of memcaches since scanners don't get created nearly as
often.
All operations other than Split lock the region for read. Locks for portions of
a region will be contended at the column level.
Splits need to lock the region for write since this is the only operation that
cannot proceed in parallel with others.
> [hbase] Increase parallelism in region servers
> ----------------------------------------------
>
> Key: HADOOP-2139
> URL: https://issues.apache.org/jira/browse/HADOOP-2139
> Project: Hadoop
> Issue Type: Improvement
> Components: contrib/hbase
> Affects Versions: 0.16.0
> Reporter: Jim Kellerman
> Assignee: Jim Kellerman
> Fix For: 0.16.0
>
>
> There are a number of paths in the region server which block against one
> another including:
> - log rolling
> - cache flushes
> - region splitting
> - updates
> - scanners
> Investigate which can proceed in parallel and mechanisms for making some
> operations that currently do not run in parallel.
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