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https://issues.apache.org/jira/browse/HBASE-24742?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17157807#comment-17157807
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Bharath Vissapragada commented on HBASE-24742:
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> I think the discussion in HBASE-17958 is enough to show that the logic is
> necessary
Yep, not suggesting that we undo that patch. Instead we should comprehensively
fix the codepaths to not do extra byte compares. So agree with you.
> I was/am planning a review of any commit that touches SQM and friends. This
> was a bit daunting because (I am guessing) the number of commits from circa
> 1.3 to 2.2 is more than a handful.
[~apurtell] look at the flame graph I attached. I also noticed the bump in
number of re-seeks. Based on my analysis I think HBASE-17958 is related, there
are more cases where the skip hinting fails in the above code I pasted. Overall
I think both the issues are related. We just tested a part of the fix (which is
reduce the number of byte comparisons) but we need to analyze the code properly
to see where the hinting fails and then re-seeks, which is essentially your
jira.
> Improve performance of SKIP vs SEEK logic
> -----------------------------------------
>
> Key: HBASE-24742
> URL: https://issues.apache.org/jira/browse/HBASE-24742
> Project: HBase
> Issue Type: Bug
> Components: Performance, regionserver
> Affects Versions: 3.0.0-alpha-1, 1.7.0, 2.4.0
> Reporter: Lars Hofhansl
> Assignee: Lars Hofhansl
> Priority: Major
> Attachments: hbase-1.6-regression-flame-graph.png,
> hbase-24742-branch-1.txt
>
>
> In our testing of HBase 1.3 against the current tip of branch-1 we saw a 30%
> slowdown in scanning scenarios.
> We tracked it back to HBASE-17958 and HBASE-19863.
> Both add comparisons to one of the tightest HBase has.
> [~bharathv]
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