RFR: 8218746: SA: Implement discontiguous bitmap for ZGC

Stefan Karlsson stefan.karlsson at oracle.com
Thu Feb 14 09:59:19 UTC 2019


On 2019-02-14 10:22, Erik Österlund wrote:
> Hi Stefan,
> 
> At ZExternalBitMap line 22:
> * Maybe add a bounds check for offsets < 0 as well.
> 
> At ZExternalBitMap line 45:
> * Remove weird whitespace in argument list.
> * Consider inverting the condition to early exit. Don't mind if you 
> choose to do that or not.
> 
> Otherwise looks good. Don't need another webrev.

I'll fix. Thanks for reviewing.

StefanK

> 
> Thanks,
> /Erik
> 
> On 2019-02-11 14:55, Stefan Karlsson wrote:
>> Hi all,
>>
>> Please review this patch to implement a discontiuous bitmap for ZGC in 
>> the SA.
>>
>> http://cr.openjdk.java.net/~stefank/8218746/webrev.01/
>> https://bugs.openjdk.java.net/browse/JDK-8218746
>>
>> ZGC uses a 16TB virtual memory address range, so the normal scheme to 
>> map a bitmap over the entire address range uses too much memory. This 
>> patch lazily creates smaller bitmaps per ZPage, when at() or atPut() 
>> is called.
>>
>> This patch builds upon JDK-8218743.
>>
>> Tested with serviceability/sa and manually running Reverse Object 
>> Analysis in the SA.
>>
>> Thanks,
>> StefanK


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