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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 Fri, 08 Feb 2008 09:21:09 GMT

    [ https://issues.apache.org/jira/browse/HARMONY-5396?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12566966#action_12566966

Egor Pasko commented on HARMONY-5396:

OK, I just need to fix the flag to be a member of ValueMethodProfile.

on the nopping:

since it looks like a VM helper call with parameters is a big chunk of code, actually my idea
is to make a jump over the call, that is how we can make it atomic, fast and not bother with
calling conventions. There are 2 ways to do this:
1. make a conditional jump during the code generation, then patch the condition
2. patch the address, where VM helper begins (not sure we can, I am not a guru in x86 asm:)

DrlEMImpl.h has an interface to notify a JIT that profile is ready:
void (*profile_notification_callback)(JIT_Handle, PC_Handle, Method_Handle);

(interface was introduced in HARMONY-4875)

not a trivial thing, I would prefer to move the discussion to the mailing list

on failing:

I prefer to fail when settings are incorrect, or at least give a warning, otherwise it is
not easy to figure out why your configuration changes did not produce any effect (a mere misprint
can cost you an hour of debugging)

> [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,
> 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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