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https://issues.apache.org/jira/browse/HBASE-20716?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16528017#comment-16528017
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stack commented on HBASE-20716:
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bq. Reduced the size of method by 40 bytes.
Or, > 50%. That looks like massive savings on a bunch of methods that are on
our hot paths. Thanks [~awked06] (Thanks in particular for the jmh'ing).
> Unsafe access cleanup
> ---------------------
>
> Key: HBASE-20716
> URL: https://issues.apache.org/jira/browse/HBASE-20716
> Project: HBase
> Issue Type: Improvement
> Components: Performance
> Reporter: stack
> Assignee: Sahil Aggarwal
> Priority: Critical
> Labels: beginner
> Attachments: HBASE-20716.master.001.patch, Screen Shot 2018-06-26 at
> 11.37.49 AM.png
>
>
> We have two means of getting at unsafe; UnsafeAccess and then internal to the
> Bytes class. They are effectively doing the same thing. We should have one
> avenue to Unsafe only.
> Many of our paths to Unsafe via UnsafeAccess traverse flags to check if
> access is available, if it is aligned and the order in which words are
> written on the machine. Each check costs -- especially if done millions of
> times a second -- and on occasion adds bloat in hot code paths. The unsafe
> access inside Bytes checks on startup what the machine is capable off and
> then does a static assign of the appropriate class-to-use from there on out.
> UnsafeAccess does not do this running the checks everytime. Would be good to
> have the Bytes behavior pervasive.
> The benefit of one access to Unsafe only is plain. The benefits we gain
> removing checks will be harder to measure though should be plain when you
> disassemble a hot-path; in a (very) rare case, the saved byte codes could be
> the difference between inlining or not.
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