RFR: 8222480: Implementation: JEP 351: ZGC: Uncommit Unused Memory

[Per Liden]

Hi,

Additional performance testing uncovered a regression in the allocation 
path, due to the removal of the ZPreMapped class. This was fixed, by 
priming the page cache with the initial heap size, and allowing the page 
cache to split pages. This also helps avoid a certain class of page 
cache evictions, where we can simply split a page instead.

Diff: http://cr.openjdk.java.net/~pliden/8222480/webrev.2-diff
Full: http://cr.openjdk.java.net/~pliden/8222480/webrev.2

cheers,
Per

On 4/23/19 3:26 PM, Per Liden wrote:
> Hi,
> 
> I sat down with Stefan to review this. A few adjustments where made.
> 
> Updated webrev:
> 
> Diff: http://cr.openjdk.java.net/~pliden/8222480/webrev.1-diff
> Full: http://cr.openjdk.java.net/~pliden/8222480/webrev.1
> 
> /Per
> 
> On 4/15/19 11:34 AM, Per Liden wrote:
>> Please review the implementation for JEP 351: ZGC: Uncommit Unused 
>> Memory.
>>
>> Once the review has been completed, I intend to move the JEP to 
>> Proposed To Target for JDK 13.
>>
>> The JEP has been updated to reflect the latest state of the 
>> implementation.
>>
>> Testing: Passes tier1-3 on all Oracle platformsm and tier1-7 on 
>> Linux/x86_64.
>>
>> JEP: https://bugs.openjdk.java.net/browse/JDK-8220347
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8222480
>> Webrev: http://cr.openjdk.java.net/~pliden/8222480/webrev.0
>>
>> /Per