RFR: 8059066: CardTableModRefBS might commit the same page twice

Erik Helin erik.helin at oracle.com
Tue Nov 25 09:17:54 UTC 2014


On 2014-11-24, Kim Barrett wrote:
> On Nov 24, 2014, at 11:09 AM, Erik Helin <erik.helin at oracle.com> wrote:
> > also added an assert to
> > how that new_end_aligned <= _committed[ri].end() always is true.
> 
> Based on your earlier analysis about there being at most one
> overlapping page, I think a tighter assertion could be used, e.g.
> something like
> 
> new_end_aligned <= (HeapWord*)align_ptr_up(_committed[ri].start() + 1, _page_size)
> 
> That would definitely deserve a comment though, and I'm not sure it
> adds enough to be worthwhile.
> 
> I looked a bit further down in the file, and initially worried about
> the uncommit case messing things up, but I think it shouldn't be
> possible for a committed region to have zero size because the
> associated covered region never has zero size.
> 
> > Please
> > see new webrevs at:
> > - full: http://cr.openjdk.java.net/~ehelin/8059066/webrev.01/index.html
> > - inc:  http://cr.openjdk.java.net/~ehelin/8059066/webrev.00-01/index.html
> 
> Looks good to me.

Many thanks for taking your time to review this tricky change!

Erik


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