Request for review: 6761744 Hotspot crashes if process size limit is exceeded

[Thomas Schatzl]

Hi,

On Mon, 2013-04-22 at 09:58 +0200, Bengt Rutisson wrote:
> 
> Hi Tao,
>
> On 4/19/13 7:27 PM, Tao Mao wrote:
>
> > 1. check overflow routine is wrapped up.
>
>I'm not sure we need round_up_total_reserved_and_check_overflow() since
>it is only being used in one place. 

Actually it is an interesting question why only the total of
GenCollectedHeaps is rounded up to large page size and the others are
not.

It seems that in parallel old, at these heap sizes, some code that
calculates internal alignment would result in an alignment > large page
size, so it would be okay, i.e. overflow already when adding together
the components.

At least with G1 with a 1 MB region size there might be an issue as e.g.
the perm gen size is rounded to heap region size. Or there is not an
issue at all, but why then do the rounding only for GenCollectedHeaps?

(I think the rounding can at most make the total overflow into a
resulting zero. I am not sure if the heap reserve functions give an
error if you pass a requested virtual space size of zero anyway...)

Hth,
Thomas