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From "Yu Li (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (HBASE-17747) Support both weak and soft object pool
Date Tue, 14 Mar 2017 01:10:41 GMT

    [ https://issues.apache.org/jira/browse/HBASE-17747?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15923349#comment-15923349
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Yu Li edited comment on HBASE-17747 at 3/14/17 1:09 AM:
--------------------------------------------------------

WeakObjectPool is still used in {{KeyLocker}}, we only change {{IdReadWriteLock}} to use SoftObjectPool
here. Since we didn't observe any issue in KeyLocker, maybe keep it there is good? [~anoop.hbase]


was (Author: carp84):
WeakObjectPool is still used in {{KeyLocker}}, we only change {{IdReadWriteLock}} to use SoftObjectPool
here. Since we didn't observe any issue there, maybe keep it there is good? [~anoop.hbase]

> 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, HBASE-17747.v2.patch, HBASE-17747.v3.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 in {{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 (old reference get removed and new lock object set
into {{referenceCache}}, see {{WeakObjectPool#get}}) thus slowing YGC. In distributed mode
there'll also be more lock object created with weak reference than soft reference that slowing
down the processing.
> 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 the GC issue only emerges under embedded mode with DirectOperator, in which
case all costs on the wire is removed thus produces extremely high concurrency.



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