RFR: 8157153: TestStressRSetCoarsening fails with OOM

[Mikael Gerdin]

Hi Stefan,

On 2016-05-26 17:20, Stefan Johansson wrote:
> Hi,
>
> Please review this testfix for:
> https://bugs.openjdk.java.net/browse/JDK-8157153
>
> Webrev:
> http://cr.openjdk.java.net/~sjohanss/8157153/hotspot.00/

Would it be possible to encapsulate the storage[] so that you don't have 
to put the "% storageUsedCount" all over the place?
This seems a bit fragile to me.

/Mikael

>
> Summary:
> The test sometimes fail due to running out of memory and the reason is
> that the test expects to be able to fit 2 objects of the size
> HeapRegionSize/2 into one heap region. This assumption is ok in theory,
> but if any object at all is allocated between the two allocations the
> second one will end up in a different region. The test calculates how
> many regions it should fill to get 90% of the heap used and then
> allocated twice this number of objects. In many cases this will work
> since nothing else is going on, but in some cases some other subsystem
> might start allocating objects, and this destroys the assumptions
> leading to hitting an OOME.
>
> The fix simply adds a second check to the allocation loop to stop as
> soon as the free memory drops below 10% of the heap, this also requires
> some extra limiting of the indexes used.
>
> Testing:
> * Local testing as well as runs through RBT.
>
> Thanks,
> Stefan