RFR: 8059066: CardTableModRefBS might commit the same page twice

Kim Barrett kim.barrett at oracle.com
Thu Nov 20 18:50:16 UTC 2014


On Nov 20, 2014, at 1:27 PM, Kim Barrett <kim.barrett at oracle.com> wrote:
> 
> On Nov 17, 2014, at 12:43 PM, Erik Helin <erik.helin at oracle.com> wrote:
>> 
>> Because the start is aligned down and the end is aligned up, the two
>> committed regions will always share at least one page (since the start
>> for _committed[1] will be aligned down and the end for _committed[0]
>> will be aligned up).
> 
> I’m just getting back to this today, and haven’t yet refreshed my understanding
> of the code.  However, the claim that there will be at least one shared page,
> (with followup reasoning for exactly one shared page), doesn’t seem right to me.
> It seems to me there could be zero shared pages, since _committed[1] could
> (perhaps accidentally, if not by design) be page aligned.

Hm, and it seems that committed regions are always page aligned.  I’m clearly not
understanding something yet.  Back to reading code…



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