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From "Egor Pasko (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HARMONY-5396) [drlvm][em] excess ValueProfiler locking causes degradation on JITted code with profiling
Date Tue, 12 Feb 2008 11:05:09 GMT

    [ https://issues.apache.org/jira/browse/HARMONY-5396?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12568051#action_12568051
] 

Egor Pasko commented on HARMONY-5396:
-------------------------------------

Pavel, I understand your concern, it makes sense to check the options without branching,

but:
1. ideally branches should make no slowdown because jumps are fairly static, i.e. branch predictor
should take it nicely (no guarantee on hardware, of course)
2. we yet do not have a good benchmark to look at, which a) exercises the value profiler heavily
b) is sensitive to changes to profile precision (lots of options for effective devirt?)



> [drlvm][em] excess ValueProfiler locking causes degradation on JITted code with profiling
> -----------------------------------------------------------------------------------------
>
>                 Key: HARMONY-5396
>                 URL: https://issues.apache.org/jira/browse/HARMONY-5396
>             Project: Harmony
>          Issue Type: Improvement
>          Components: DRLVM
>            Reporter: Aleksey Shipilev
>            Assignee: Egor Pasko
>         Attachments: 0001-ValueProfileCollector-refactoring-to-separate-FirstN-and-Divided-methods.txt,
0002-value-profiling-options-locked-flagged_all-flagged_insert-unsafe.txt, 0002-ValueProfileCollector-implementing-locking-strategies.txt,
0003-value-profiling-options-locked-flagged_all-flagged_insert-unsafe.txt, HARMONY-5396-syncTie.patch
>
>
> During investigation of serious slowdown in some microbenchmark, excess locking in ValueProfiler
was identified. 
> Please see Harmony-dev thread for the details: http://markmail.org/message/tatsfbyb7eb3q3rr

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