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