[jira] [Updated] (HBASE-16278) Use ConcurrentHashMap instead of ConcurrentSkipListMap if possible

["Duo Zhang (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HBASE-16278?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Duo Zhang updated HBASE-16278:
------------------------------
    Issue Type: Improvement  (was: Bug)

> Use ConcurrentHashMap instead of ConcurrentSkipListMap if possible
> ------------------------------------------------------------------
>
>                 Key: HBASE-16278
>                 URL: https://issues.apache.org/jira/browse/HBASE-16278
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Duo Zhang
>
> SSD and 10G network make our system CPU bound again, so the speed of memory operation only code becomes more and more important.
> In HBase, if want to use byte[] as a map key, then we will always use CSLM even if we do not need the map to be ordered. I know that this could save one object allocation since we can not use byte[] directly as CHM's key. But we all know that CHM is faster than CSLM, so I wonder if it worth to use CSLM instead of CHM only because one extra object allocation.
> Then I wrote a simple jmh micro benchmark to test the performance of CHM and CSLM. The code could be found here
> https://github.com/Apache9/microbench
> It turns out that CHM is still much faster than CSLM with one extra object allocation.
> So I think we should always use CHM if we do not need the keys to be sorted.



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