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https://issues.apache.org/jira/browse/HBASE-7295?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13639262#comment-13639262
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Varun Sharma commented on HBASE-7295:
-------------------------------------
I attached two files comparing performance of volatile and synchronized
simulating a behaviour similar to HBaseClient using a PoolMap<String, String>
The tests basically run 1000 threads which issue 10000 calls and each call
performs an operation on PoolMap 30 times. So 300 million times.
Results
1) Synchronized - 90 seconds
2) Volatile - 16 seconds
As you can see, volatile is almost an order of magnitude faster.
That said, it seems like we can do this kind of locking almost 3 million times
per second on a simple computer which is, for most cases, enough.
> Contention in HBaseClient.getConnection
> ---------------------------------------
>
> Key: HBASE-7295
> URL: https://issues.apache.org/jira/browse/HBASE-7295
> Project: HBase
> Issue Type: Improvement
> Affects Versions: 0.94.3
> Reporter: Varun Sharma
> Assignee: Varun Sharma
> Attachments: 7295-0.94.txt, 7295-0.94-v2.txt, 7295-0.94-v3.txt,
> 7295-0.94-v4.txt, 7295-0.94-v5.txt, 7295-trunk.txt, 7295-trunk.txt,
> 7295-trunk-v2.txt, 7295-trunk-v3.txt, 7295-trunk-v3.txt, 7295-trunk-v4.txt,
> synchronized_output.txt, TestSynchronized.java, TestVolatile.java,
> volatile_output.txt
>
>
> HBaseClient.getConnection() synchronizes on the connections object. We found
> severe contention on a thrift gateway which was fanning out roughly 3000+
> calls per second to hbase region servers. The thrift gateway had 2000+
> threads for handling incoming connections. Threads were blocked on the
> syncrhonized block - we set ipc.pool.size to 200. Since we are using
> RoundRobin/ThreadLocal pool only - its not necessary to synchronize on
> connections - it might lead to cases where we might go slightly over the
> ipc.max.pool.size() but the additional connections would timeout after
> maxIdleTime - underlying PoolMap connections object is thread safe.
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