RFR (S): JDK-8076241: Remove unused methods mod_card_iterate() and non_clean_card_iterate_serial()

Kim Barrett kim.barrett at oracle.com
Mon Mar 30 22:16:09 UTC 2015

On Mar 30, 2015, at 10:18 AM, Bengt Rutisson <bengt.rutisson at oracle.com> wrote:
> Hi all,
> Could I have a couple of reviews for this small change?
> http://cr.openjdk.java.net/~brutisso/8076241/webrev.00/
> https://bugs.openjdk.java.net/browse/JDK-8076241
> The methods mod_card_iterate() and non_clean_card_iterate_serial() in CardTableModRefBS are not being used.
> Thanks,
> Bengt

Aww. I was going to do that. Actually, I was supposed to file a RFE
for this as a followup to 8062206 (Remove unusable
G1RSLogCheckCardTable command line argument), but that seems to have
not gotten out of my notes file.

 181   // XXX ??? MemRegionClosure above vs OopsInGenClosure below XXX
 182   // XXX some new_dcto_cl's take OopClosure's, plus as above there are
 183   // some MemRegionClosures. Clean this up everywhere. XXX

This untouched comment is referring to the removed
non_clean_card_iterate_serial function ("above"), so needs to be
updated. It may be that the comment can be removed entirely now,
possibly being moved to the technical debt wiki.

 382   // Invoke "cl.do_MemRegion" on a set of MemRegions that collectively
 383   // includes all the modified cards (expressing each card as a
 384   // MemRegion).  Thus, several modified cards may be lumped into one
 385   // region.  The regions are non-overlapping, and are visited in
 386   // *decreasing* address order.  (This order aids with imprecise card
 387   // marking, where a dirty card may cause scanning, and summarization
 388   // marking, of objects that extend onto subsequent cards.)

This comment was the reason I'd deferred removing mod_card_iterate. So
far as I can tell, this comment is the *only* place where there is any
discussion whatsoever of why some card iterators scan backward. I
wanted to find a new and better home for that information before
deleting the comment.


The code changes look good.

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