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https://issues.apache.org/jira/browse/HBASE-20716?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16636829#comment-16636829
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Anoop Sam John commented on HBASE-20716:
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Ya one class for Unsafe. That will be the best!. Both Utils can make use of
that. We have the Comparor and Converter now.
The Unsafe or PureJava version does not need to keep any static singleton ref.
The Comparator/Convertor bridge as such can have a ref to this interface type
which refers to the singleton best instance. That loading of Unsafe version
class also should be via FQCN. Or else we have the UnsafeAvailChecker now..
Can just make use of that (static methods on that) to know whether Unsafe is
available and can be used and based on that can instantiate the
Convertor/Comparator class.
> Unsafe access cleanup
> ---------------------
>
> Key: HBASE-20716
> URL: https://issues.apache.org/jira/browse/HBASE-20716
> Project: HBase
> Issue Type: Sub-task
> Components: Performance
> Reporter: stack
> Assignee: Sahil Aggarwal
> Priority: Critical
> Labels: beginner
> Attachments: HBASE-20716.master.001.patch,
> HBASE-20716.master.002.patch, HBASE-20716.master.003.patch,
> HBASE-20716.master.004.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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