RFR (S): 8067469: G1 ignores AlwaysPreTouch

[David Holmes]

Hi Thomas,

On 16/12/2014 10:23 PM, Thomas Schatzl wrote:
> Hi all,
>
>    can I have reviews for the following small change?
>
> It adds pre-touching of allocated memory in G1, which has been forgotten
> to be implemented when changing this code in JDK-8038423.
>
> This change adds this and refactors the pre-touch code to a single
> method in the os class.
>
> CC'ed runtime since it changes code in os.hpp/cpp.

Just looking at that, we seem to be assuming/requiring that start and 
end are suitably page aligned and/or an integral number of pages apart - 
otherwise for an arbitrary pair of addresses it seems we could fail to 
touch the page containing end.

David

> CR:
> https://bugs.openjdk.java.net/browse/JDK-8067469
> Webrev:
> http://cr.openjdk.java.net/~tschatzl/8067469/webrev/
>
> Testing:
> jprt, manual testing with and without AlwaysPreTouch enabled
>
> Thanks,
>    Thomas
>
>