RFR (S/M): 8184348: Merge G1ConcurrentMark::par_mark() and G1ConcurrentMark::grayRoot()

[Aleksey Shipilev]

On 07/14/2017 04:34 PM, Thomas Schatzl wrote:
> Thanks. Unfortunately, after re-appyling and fixing other changes based
> on this one I noticed that I missed one opportunity to refactor in
> G1CMTask::deal_with_reference(). I would like to add this to this
> changeset still... sorry.
> 
> There is some note about some perf optimization that mentions that it
> is advantagous to do the nTAMS check before determining the heap
> region; however I do not think this is an issue.
> 
> Quickly comparing runs of a fairly large and reference-intensive
> workload (BigRAMTester with 20g heap e.g. attached to JDK-8152438),
> marking cycles with the latest webrev.2 are at least as fast as without
> any of this RFR's changes.
> 
> New webrevs:
> http://cr.openjdk.java.net/~tschatzl/8184348/webrev.1_to_2 (diff)
> http://cr.openjdk.java.net/~tschatzl/8184348/webrev.2 (full)

Looks good.

I wonder what this was about in the old code:

 187   if (_g1h->is_in_g1_reserved(objAddr)) {

New code properly asserts the object is in reserved. Did we ever had oops stored
outside of reserved? That would be surprising!

Thanks,
-Aleksey



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