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From "Aleksey Shipilev (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 22:59:08 GMT

    [ https://issues.apache.org/jira/browse/HARMONY-5396?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12568351#action_12568351

Aleksey Shipilev commented on HARMONY-5396:

Egor, there is *CRASH* in server_aggressive, because no default option for updateStrategy
is specified, so we need to commit the fix for that ASAP.  Maybe we might ask Mikhail F. or
Alexey V. for help?

As for atomic increments, there are two approaches: 
 a. implementing *spin-loop* with atomic increment - but who will arbiter that in case of
contention? I don't believe this is right.
 b. implementing fast atomic increment with falling back to mutex in case of contention. Linux
has such thing as "futex".

 I think it should be more general approach, not only the ValueProfiler related. For example,
try to migrate significant parts of framework from hymutex_lock/unlock to hyfutex_lock/unlock.
That deserves separate thread.

> [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, 0004-value-profiling-reviving-locked-profile.txt,
> 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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