[HBASE-16278] Use ConcurrentHashMap instead of ConcurrentSkipListMap if possible

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Assignee: Unassigned
• Reporter: Duo Zhang
• Created: 23/Jul/16 07:17
• Updated: 25/Jul/16 08:17

Description

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.

Sub-Tasks

• Use hash based map in SequenceIdAccounting: Resolved
• Use CHM instead of CLSM in TableAuthManager: Resolved