RFR (S): 8051973: Eager reclaim leaves marks of marked but reclaimed objects on the next bitmap

[Bengt Rutisson]

Hi Thomas,

Looks good.

One minor question about this code:


6609     // Need to clear mark bit of the humongous object if already set.
6610     if (next_bitmap->isMarked(r->bottom())) {
6611       next_bitmap->clear(r->bottom());
6612     }

Is it worth checking if the bit is marked or should we just 
unconditionally clear it?

Thanks,
Bengt


On 2014-07-30 13:29, Thomas Schatzl wrote:
> Hi Jon,
>
>    thanks for the review.
>
> On Tue, 2014-07-29 at 13:50 -0700, Jon Masamitsu wrote:
>> On 7/29/2014 3:40 AM, Thomas Schatzl wrote:
>>> Hi all,
>>>
>>>     can I have reviews for the following small change?
>>>
>>> JDK-8027959 implemented eager reclaim of humongous objects, which
>>> potentially left stray set marks on the mark bitmap after reclaiming a
>>> region.
>>>
>>> This change fixes this.
>>>
>>> CR:
>>> https://bugs.openjdk.java.net/browse/JDK-8051973
>>> Webrev:
>>> http://cr.openjdk.java.net/~tschatzl/8051973/webrev/
>> The changes look good.
>>
>> You left the uses  r->bottom() so you would not
>> have to cast obj to HeapWord*?
> Yes. If you have objections to that I can change that back. The code is
> easier to read for me if there is not that much casting.
>
>> Do you want to specify a region size in the test?  Current
>> policy would have  regions sizes such that
>>
>>     48     public static final int M = 1024*1024;
>>
>> gives you humongous allocations but policy could change, yes?
> Done.
>
> See
> http://cr.openjdk.java.net/~tschatzl/8051973/webrev.0_to_1
> Full webrev:
> http://cr.openjdk.java.net/~tschatzl/8051973/webrev.1
>
> Thomas
>
>