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From "Yu Li (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-17747) Support both weak and soft object pool
Date Wed, 08 Mar 2017 05:59:37 GMT

    [ https://issues.apache.org/jira/browse/HBASE-17747?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15900770#comment-15900770

Yu Li commented on HBASE-17747:

bq. So here there is no change in usage of soft ref instead of weak.. Just you doing the abstraction
and giving both impls so as to make a way for the embedded mode usage.
{{IdReadWriteLock}} has been changed to use soft reference, please check the change there
and let me know if any concern sir [~anoop.hbase], thanks.

> Support both weak and soft object pool
> --------------------------------------
>                 Key: HBASE-17747
>                 URL: https://issues.apache.org/jira/browse/HBASE-17747
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Yu Li
>            Assignee: Yu Li
>         Attachments: HBASE-17747.patch
> During YCSB testing on embedded mode after HBASE-17744, we found that under high read
load GC is quite severe even with offheap L2 cache. After some investigation, we found it's
caused by using weak reference for IdReadWriteLock. In embedded mode the read is so quick
that the lock might already get promoted to the old generation when the weak reference is
cleared, which causes dirty card table thus slowing YGC.
> So we proposed to use soft reference for this IdReadWriteLock used in cache, which won't
get cleared until JVM memory is not enough, and could resolve the issue mentioned above. What's
more, we propose to extend the WeakObjectPool to be more generate to support both weak and
soft reference.
> Note that this issue only emerges under embedded mode with DirectOperator, in which case
all costs on the wire is removed thus produces extremely high workloads.

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