RFR 8067655: Clean up G1 remembered set oop iteration

Mikael Gerdin mikael.gerdin at oracle.com
Wed Dec 17 08:52:53 UTC 2014


Hi,

On 2014-12-16 15:33, Mikael Gerdin wrote:
> Hi all,
>
> while reading through the code which iterates over oops pointing into
> the collection set I noticed that the closure used to implement the
> iteration, G1ParPushHeapRSClosure, is hooked into the de-virtualization
> macros with oop_oop_iterate_nv but the static type is not preserved all
> the way down to the call site where oop_iterate is called, so the
> de-virtualization cannot work.
>
> I fixed the code to pass down the correct type and while doing that I
> had to clean up some dead code, such as the FilterKind parameter to the
> HeapRegionDCTOC which was only ever used with the IntoCSFilterKind. The
> filtering is not needed at all since G1ParPushHeapRSClosure already does
> a collection set check so I removed the filtering altogether.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8067655
> Webrev: http://cr.openjdk.java.net/~mgerdin/8067655/webrev.0/

New webrev based on feedback from Jon and Kim:

Incremental webrev:
http://cr.openjdk.java.net/~mgerdin/8067655/webrev.0_to_1/
Full webrev:
http://cr.openjdk.java.net/~mgerdin/8067655/webrev.1/

/Mikael

>
> Testing:
> JPRT, jbb2005 on x86_64 and sparc.
> The jbb runs showed no significant changes and the ScanRS time changes
> are inconclusive but I still think this is a nice cleanup change. At
> least this change makes it clear that it's actually only one closure
> type which is used by the HeapRegionDCTOC.
>
> /Mikael


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