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https://issues.apache.org/jira/browse/HBASE-20188?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16433710#comment-16433710
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Eshcar Hillel commented on HBASE-20188:
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And another thing, might be just a distraction but we think it is worth 
mentioning –
Backward scans should run faster with IMC since the flat segments are simply 
arrays and it is very simple to go to prev in O(1), while in skip list prev is 
implemented by seeking the prev key which is done in O(log n).
We don't have an easy way to verify this since YCSB does not support testing 
this kind of operation, but we are looking into it and will report if something 
interesting comes up. 

> [TESTING] Performance
> ---------------------
>
>                 Key: HBASE-20188
>                 URL: https://issues.apache.org/jira/browse/HBASE-20188
>             Project: HBase
>          Issue Type: Umbrella
>          Components: Performance
>            Reporter: stack
>            Assignee: stack
>            Priority: Blocker
>             Fix For: 2.0.0
>
>         Attachments: CAM-CONFIG-V01.patch, HBASE-20188-xac.sh, 
> HBASE-20188.sh, HBase 2.0 performance evaluation - 8GB(1).pdf, HBase 2.0 
> performance evaluation - 8GB.pdf, HBase 2.0 performance evaluation - Basic vs 
> None_ system settings.pdf, ITBLL2.5B_1.2.7vs2.0.0_cpu.png, 
> ITBLL2.5B_1.2.7vs2.0.0_gctime.png, ITBLL2.5B_1.2.7vs2.0.0_iops.png, 
> ITBLL2.5B_1.2.7vs2.0.0_load.png, ITBLL2.5B_1.2.7vs2.0.0_memheap.png, 
> ITBLL2.5B_1.2.7vs2.0.0_memstore.png, ITBLL2.5B_1.2.7vs2.0.0_ops.png, 
> ITBLL2.5B_1.2.7vs2.0.0_ops_NOT_summing_regions.png, YCSB_CPU.png, 
> YCSB_GC_TIME.png, YCSB_IN_MEMORY_COMPACTION=NONE.ops.png, YCSB_MEMSTORE.png, 
> YCSB_OPs.png, YCSB_in-memory-compaction=NONE.ops.png, YCSB_load.png, 
> flamegraph-1072.1.svg, flamegraph-1072.2.svg, hbase-env.sh, hbase-site.xml, 
> hbase-site.xml, lock.127.workloadc.20180402T200918Z.svg, 
> lock.2.memsize2.c.20180403T160257Z.svg, run_ycsb.sh, tree.txt, workloadx, 
> workloadx
>
>
> How does 2.0.0 compare to old versions? Is it faster, slower? There is rumor 
> that it is much slower, that the problem is the asyncwal writing. Does 
> in-memory compaction slow us down or speed us up? What happens when you 
> enable offheaping?
> Keep notes here in this umbrella issue. Need to be able to say something 
> about perf when 2.0.0 ships.



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