RFR(s): 8152160: SIGFPE in CompactibleFreeListSpaceLAB::compute_desired_plab_size

[Per Liden]

Hi Sangheon,

On 2016-03-22 03:12, sangheon wrote:
> Hi all,
>
> Could I have a couple of reviews for this change?
>
> With large value of CMSOldPLABNumRefills, SIGFPE would happen at
> CompactibleFreeListSpaceLAB::compute_desired_plab_size() because related
> routine would be zero by an overflow.
>
> Type-casting to 'double' before the problematic division will resolve
> the problem.

Casting to double doesn't quite seem like the right thing to do here. 
Can't this be rephrased to avoid the overflow completely, something like:

_global_num_blocks[i] / _global_num_workers[i] / CMSOldPLABNumRefills

cheers,
Per

>
> CR: https://bugs.openjdk.java.net/browse/JDK-8152160
> Webrev: http://cr.openjdk.java.net/~sangheki/8152160/webrev.00
> Testing: JPRT, TestOptionsWithRanges.java via RBT and manual test as CR
> description.
>
> Thanks,
> Sangheon
>
>
>