RFR: 8245106: ZGC: Fix incorrect setup when using -XX:+UseTransparentHugePages

[Per Liden]

Thanks Erik!

/Per

On 5/18/20 2:26 PM, Erik Österlund wrote:
> Hi Per,
> 
> Looks good.
> 
> Thanks,
> /Erik
> 
> On 2020-05-15 14:04, Per Liden wrote:
>> When using -XX:+UseTransparentHugePages, ZGC mistakenly calls 
>> madvise(..., MADV_HUGE); too late. The end result is that large pages 
>> are never allocated on first page fault, only via THP defrag. This in 
>> turn means that the majority of the heap will typically not be backed 
>> by large pages, which can have a very noticeable performance impact.
>>
>> This patch depends on "8245098: Make SafeFetch32/N available earlier", 
>> which is currently out for review on hotspot-dev.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8245106
>> Webrev: http://cr.openjdk.java.net/~pliden/8245106/webrev.0
>>
>> /Per
>