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From "Aleksey Shipilev" <aleksey.shipi...@gmail.com>
Subject Re: [jira] Created: (HARMONY-5713) [drlvm][performance] Implementation of System.identityHashCode() on magics
Date Fri, 11 Apr 2008 07:02:38 GMT
Hi, Xiao Feng!

Thank you for the interest in this issue. Let me explain a bit about
these JIRAs.

Originally there was the problem discovered with
System.identityHashCode [1] and proposed patch with draft
implementation of GCHelper for iHC. The problem there though is lack
of bindings of such the helper to actual VM. As the proof-of-concept
there was hack in kernel classes which called GCHelper explicitly,
this is for sure non-portable way and sticks VM to exact GC compiled
against.

To tolerate this inconvenience, I had to make VM helper, bind GCHelper
to VM helper at runtime, then use power of helper inliner to actually
include the code into execution path, this is subtask in
j.l.ThreadLocal [2]. This patch is still dirty, as it works only on my
microtest, but Dacapo and some other workloads still fails. I will try
to fix the problem in near term, you're welcome to fresh JIRA [2]. Do
you like for patch to be splitted in GC/VM/JIT parts?

BTW, can you point me to code or docs where I can get more info on
hashcode computation in GCv5? I'm particularly interested in hashcode
states (HASHCODE_SET_ATTACHED, HASHCODE_SET_ATTACHED,
HASHCODE_SET_BUFFERED), that would help me to understand the code in
helper. F.ex. I haven't idea why HASHCODE_SET_BUFFERED is not covered
by helper.

And some good news: draft helper gives 2.5x boost on ThreadLocal
benchmark, and I expect more since I had a look into generated JITted
code.

Thanks,
Aleksey.

[1] https://issues.apache.org/jira/browse/HARMONY-4551
[2] https://issues.apache.org/jira/browse/HARMONY-5713

On Fri, Apr 11, 2008 at 5:07 AM, Xiao-Feng Li <xiaofeng.li@gmail.com> wrote:
> Aleksey, is this patch supposed to be committed? I guess some
>  committer on perf would take care of it? If not, I can commit it.
>
>  Thanks,
>  xiaofeng
>
>
>
>  On Fri, Apr 11, 2008 at 12:08 AM, Aleksey Shipilev (JIRA)
>  <jira@apache.org> wrote:
>  > [drlvm][performance] Implementation of System.identityHashCode() on magics
>  >  --------------------------------------------------------------------------
>  >
>  >                  Key: HARMONY-5713
>  >                  URL: https://issues.apache.org/jira/browse/HARMONY-5713
>  >              Project: Harmony
>  >           Issue Type: Sub-task
>  >             Reporter: Aleksey Shipilev
>  >
>  >
>  >  This is the working sub-task for implementation of System.identityHashCode() on
magics, inspired by HARMONY-4551.
>  >
>  >  --
>  >  This message is automatically generated by JIRA.
>  >  -
>  >  You can reply to this email to add a comment to the issue online.
>  >
>  >
>
>
>
>  --
>  http://xiao-feng.blogspot.com
>

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