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From "Yu Li (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-17747) Support both weak and soft object pool
Date Mon, 13 Mar 2017 10:37:04 GMT

     [ https://issues.apache.org/jira/browse/HBASE-17747?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Yu Li updated HBASE-17747:
--------------------------
    Description: 
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.

  was:
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.


> 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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