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From "Aleksey Shipilev (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HARMONY-4705) [drlvm][jni] JNI transition uses ineffective TLS get
Date Mon, 03 Sep 2007 10:47:18 GMT

    [ https://issues.apache.org/jira/browse/HARMONY-4705?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12524494
] 

Aleksey Shipilev commented on HARMONY-4705:
-------------------------------------------

Good catch, Sergey, thanks! That's due to implementation of helper for Linux/ia32. Please
see HARMONY-4723 for the details. Together HARMONY-4723 and this issue work fine on Linux/ia32.

> [drlvm][jni] JNI transition uses ineffective TLS get
> ----------------------------------------------------
>
>                 Key: HARMONY-4705
>                 URL: https://issues.apache.org/jira/browse/HARMONY-4705
>             Project: Harmony
>          Issue Type: Improvement
>          Components: DRLVM
>            Reporter: Aleksey Shipilev
>         Attachments: JNI-tls-1.patch
>
>
> For now, JNI transition uses ineffective scheme of TLS getting - it is done via several
recursive calls, finally reaching hythread_self().
> The idea is to inline helper for TLS get instead of calling get_thread_ptr_stub(). Disassembly
shows that 10 push/pops and 3 calls are completely eliminated there, keeping in mind that
TLS get occurs at least 3 times on each JNI transition this give us a huge boost, eliminating
up to 30 push/pops and 9 calls.
> JNI microtest (calling several millions of empty JNI methods) testifies this:
> $ ../../Builds/Harmony-clean/bin/java -cp . -Xmx128m -Xms128m nalog.nalog
> iteration: 0  millis:8763
> iteration: 1  millis:8722
> iteration: 2  millis:8833
> $ ../../Builds/Harmony-fastTLS-1/bin/java -cp . -Xmx128m -Xms128m nalog.nalog
> iteration: 0  millis:6780
> iteration: 1  millis:6689
> iteration: 2  millis:6870

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