RFR (S/M): 8169703: G1 crashes with guarantee(pretouch_gang != NULL) failed: No pretouch gang specified

[Kim Barrett]

> On Nov 18, 2016, at 3:47 AM, Thomas Schatzl <thomas.schatzl at oracle.com> wrote:
> 
> Hi all,
> 
>   can I have reviews for this change that fixes use of AlwaysPreTouch
> with CDS?
> 
> Basically, AlwaysPreTouch is apparently not used very often, so some
> use cases were missed, causing a guarantee to fail.
> 
> The patch adds support for:
>  - parallel pretouch during (potentially concurrent) humongous object
> allocation.
>  - allocating CDS/archive regions during archive creation. In this case
> the code uses only one thread because archive regions are always
> allocated region by region anyway.
>  - mapping in a memory range covered by a CDS archive
> 
> All these cases are covered by new regression tests.
> 
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8169703
> Webrev:
> http://cr.openjdk.java.net/~tschatzl/8169703/webrev/
> Testing:
> runtime tier0-5 tests with -XX:+AlwaysPreTouch, new tests
> 
> Thanks,
>   Thomas

Collector changes look good.

I didn’t spot any issues with the tests that weren’t already noted by Dmitry.