Differences between openjdk6 hotspot and hs14+

[Andrew John Hughes]

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
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