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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-9969) Improve KeyValueHeap using loser tree
Date Fri, 15 Nov 2013 05:55:33 GMT

    [ https://issues.apache.org/jira/browse/HBASE-9969?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13823319#comment-13823319
] 

Lars Hofhansl commented on HBASE-9969:
--------------------------------------

Tested again without performing a major compaction. In my scenario I have 10m rows with 5
columns each. Ends up being only three regions and only that last one has more than one store
file (4 in this case).
With that I still did not see any improvement.

Re: HBASE-9778, it's still not immediately clear there how to optimize the cases mentioned
there (many small KVs) while keeping other optimizations (for example for large KVs, where
the likelihood is high that a call to next() will land us unnecessarily in the next block).

Anything that will bring HBase's CPU consumption down is a win. Unless all data is in the
cache I would expect us always being CPU bound, that is not always true (with SSDs for example).


> Improve KeyValueHeap using loser tree
> -------------------------------------
>
>                 Key: HBASE-9969
>                 URL: https://issues.apache.org/jira/browse/HBASE-9969
>             Project: HBase
>          Issue Type: Improvement
>          Components: Performance, regionserver
>            Reporter: Chao Shi
>            Assignee: Chao Shi
>             Fix For: 0.98.0, 0.96.1
>
>         Attachments: hbase-9969-v2.patch, hbase-9969.patch, hbase-9969.patch, kvheap-benchmark.png,
kvheap-benchmark.txt
>
>
> LoserTree is the better data structure than binary heap. It saves half of the comparisons
on each next(), though the time complexity is on O(logN).
> Currently A scan or get will go through two KeyValueHeaps, one is merging KVs read from
multiple HFiles in a single store, the other is merging results from multiple stores. This
patch should improve the both cases whenever CPU is the bottleneck (e.g. scan with filter
over cached blocks, HBASE-9811).
> All of the optimization work is done in KeyValueHeap and does not change its public interfaces.
The new code looks more cleaner and simpler to understand.



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