RFR (M): 8224741: Optimize the scan area during the Scan Heap Roots phase

[Leo Korinth]

Looks great.

Thanks,
Leo

On 04/07/2019 11:28, Thomas Schatzl wrote:
> Hi Kim,
> 
> On Wed, 2019-07-03 at 17:06 -0400, Kim Barrett wrote:
>>> On Jul 3, 2019, at 5:17 AM, Thomas Schatzl <
>>> thomas.schatzl at oracle.com> wrote:
>>>> src/hotspot/share/gc/g1/heapRegion.inline.hpp
>>>> 296     // If obj is not an objArray and mr contains the start of
>>>> the
>>>> 297     // obj, then this could be an imprecise mark, and we need
>>>> to
>>>> 298     // process the entire object.
>>>> 299     int size = obj->oop_iterate_size(cl);
>>>> 300     return MAX2((HeapWord*)obj + size, mr.end());
>>>>
>>>> Maybe mention here also that there aren't any objects after obj
>>>> in the region.
>>>
>>> Fixed.
>>
>>   300     // There are no objects after this humongous object in the
>> region, so we
>>   301     // can return the end of the object.
>>
>> That’s not quite what I had in mind.  I was thinking something like
>>
>> We've scanned to the end of the object, but since there are no
>> objects after this humongous object in the region, we can return the
>> end of the region of that's greater.
> 
> Fixed according to your suggestion.
> 
>>
>>> http://cr.openjdk.java.net/~tschatzl/8224741/webrev.1_to_2 (diff)
>>> http://cr.openjdk.java.net/~tschatzl/8224741/webrev.2 (full)
>>>
>>> (These are only comment adjustments as suggested here, so no
>>> testing)
>>
>> Looks good, other than the above suggested further comment tweak.
> 
> Leo also found a superfluous size_t cast that I removed in the webrevs
> below:
> 
> http://cr.openjdk.java.net/~tschatzl/8224741/webrev.2_to_3 (diff)
> http://cr.openjdk.java.net/~tschatzl/8224741/webrev.3 (full)
> 
> 
> Thanks,
>    Thomas
>