RFR (S): 7080389: G1: refactor marking code in evacuation pause copy closures
bengt.rutisson at oracle.com
Fri Aug 19 06:01:13 PDT 2011
Looks good to me.
A couple of minor comments:
In the do_oop_work method (lines 4324-4362):
* To show the limited scope of the should_mark variable I would like to
move the declaration of should_mark to just before it is being used at
* At the two places in the do_oop_work method where you use the
do_mark_forwardee paramter you have comments saying that it is an
initial mark closure. This is correct, so I think that I would actually
prefer that the parameter was called something with inital mark rather
than having to have the comments.
* On the dead code subject: this closure seems to be unused (in
Just a nitpick: You removed a line break at row 114 and added a line
break at row 122-123. Since you didn't change anything else on these
lines it would make the diff easier to view if you left those changes out.
On 2011-08-18 20:17, John Cuthbertson wrote:
> Hi Everyone,
> Can I have a couple of volunteers review these refactoring changes to
> the marking code used during evacuation pauses (both initial mark
> pauses and regular evacuation pauses when marking is active) - the
> change can be found at
> The refactoring changes fix an issue that was seen with the code
> changes for 6486945.
> During an initial mark pause, during root scanning, one thread had
> successfully forwarded an object and had started to copy it. While the
> object was being copied to its new location, another thread saw that
> the object had been forwarded and, after checking that the new
> location was unmarked, successfully marked the new location. The first
> thread would finish the copying, see that the new location was marked
> and skip the mark. The situation I ran into was that I was attempting
> to obtain the size of the new object just after it was marked (by the
> thread doing the marking) and the old object had not yet been fully
> copied to its new location.
> With these refactoring changes, the thread that successfully forwards
> an object in the collection set will mark the forwardee after copying
> - allowing me to safely obtain it's size.
> Testing: several runs of the GC test suite with a marking threshold of
> 10 and 20%, Kitchensink, and jprt.
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