RFR: 8062063: Usage of UseHugeTLBFS, UseLargePagesInMetaspace and huge SurvivorAlignmentInBytes cause crashes in CMBitMapClosure::do_bit

[Jon Masamitsu]

Stefan,

The CR indicates to me that the clearing would be done at the uncommit() but
this fix has the clearing done at the commit().  Am I reading the CR and 
webrev
correctly?  If so, the arguments for doing the clearing at the 
uncommit() seem
good ones.

Jon

PS.  Thanks for picking this up.

On 1/7/2015 7:14 AM, Stefan Johansson wrote:
> Hi,
>
> Please review this fix for:
> https://bugs.openjdk.java.net/browse/JDK-8062063
>
> Webrev:
> http://cr.openjdk.java.net/~sjohanss/8062063/hotspot.00
>
> Summary:
> When using large pages on Linux we never actually uncommit memory, we 
> just mark it as currently not used. When later re-committing those 
> pages we currently only mark them in use again. This works fine until 
> someone expects to get cleared memory back when doing a commit, which 
> for example is expected for the memory backing certain bitmaps. This 
> fix, makes sure that we always clear large pages when they are 
> re-committed.
>
> Testing:
> * Built via JPRT
> * Verified fix on failing reproducer
> * Planning to run longer aurora-run.
>
> Thanks,
> Stefan