Differences between openjdk6 hotspot and hs14+

[Martin Buchholz]

Looks good.

Martin

On Mon, Nov 23, 2009 at 12:16, Andrew John Hughes
<gnu_andrew at member.fsf.org> wrote:
> 2009/11/11 Martin Buchholz <martinrb at google.com>:
>> Hi Andrew,
>>
>> I'm checking the current state of hotspot 14 in openjdk6,
>> and noticed some discrepancies I can't explain.
>>
>> This hunk:
>>
>> --- /home/martinrb/ws/hsx14-master/src/share/vm/runtime/globals.hpp
>> 2009-05-13 14:49:39.000000000 -0700
>> +++ /home/martinrb/ws/openjdk6/hotspot/src/share/vm/runtime/globals.hpp
>> 2009-11-04 15:34:13.000000000 -0800
>> @@ -1494,7 +1497,7 @@
>>            "CMSPrecleanNumerator:CMSPrecleanDenominator yields convergence"
>> \
>>            " ratio")
>> \
>>
>> \
>> -  product(bool, CMSPrecleanRefLists1, true,
>> \
>> +  product(bool, CMSPrecleanRefLists1, false,
>> \
>>            "Preclean ref lists during (initial) preclean phase")
>> \
>>
>> \
>>    product(bool, CMSPrecleanRefLists2, false,
>> \
>>
>>
>> is from
>>
>> # HG changeset patch
>> # User ysr
>> # Date 1227212861 28800
>> # Node ID 00b023ae2d78987955a9647b6d6d457bd39dec7e
>> # Parent  b5e603f2e02480180ace404141897cf8f6266e93
>> 6722113: CMS: Incorrect overflow handling during precleaning of Reference
>> lists
>> Summary: When we encounter marking stack overflow during precleaning of
>> Reference lists, we were using the overflow list mechanism, which can cause
>> problems on account of mutating the mark word of the header because of
>> conflicts with mutator accesses and updates of that field. Instead we should
>> use the usual mechanism for overflow handling in concurrent phases, namely
>> dirtying of the card on which the overflowed object lies. Since precleaning
>> effectively does a form of discovered list processing, albeit with discovery
>> enabled, we needed to adjust some code to be correct in the face of
>> interleaved processing and discovery.
>> Reviewed-by: apetrusenko, jcoomes
>>
>>
>> Probably inadvertently reverted during a merge?
>>
>>
>> I found this by reviewing changes thusly
>>
>> diff -Bw -x .hg -u -r  ~/ws/hsx14-master/ ~/ws/openjdk6/hotspot/
>>
>> Martin
>>
>
> Yes, looks like it was reverted in:
>
> http://hg.openjdk.java.net/jdk6/jdk6/hotspot/rev/1ba7ca27e707
>
> (the big merge)
>
> Here's a webrev for the change:
>
> http://cr.openjdk.java.net/~andrew/jdk6-hs14-merge/webrev.05/
>
> Joe, can you please approve this and allocate it a bug ID?
>
> Thanks,
> --
> Andrew :-)
>
> Free Java Software Engineer
> Red Hat, Inc. (http://www.redhat.com)
>
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