Request for review (S): 7110718 -XX:MarkSweepAlwaysCompactCount=0 crashes the JVM

[Jon Masamitsu]

Bengt,

The change looks fine.  Did you consider making MarkSweepAlwaysCompactCount
unsigned?

Jon

On 11/14/11 01:25, Bengt Rutisson wrote:
>
> Hi all,
>
> Can I have a couple of reviews for this small change?
> http://cr.openjdk.java.net/~brutisso/7110718/webrev.01/
>
> It is a fix for the issue that Ramki reported recently. 
> MarkSweepAlwaysCompactCount is used for division and Hotspot crashes 
> if it is set to 0.
>
> I choose to log an error and exit the VM if someone tries to start 
> with -XX:MarkSweepAlwaysCompactCount=0. An alternative is to just log 
> a warning and set it to 1.
>
> I prefer the error way since it is not really clear what one wants to 
> achieve with MarkSweepAlwaysCompactCount=0. Always do full compactions 
> or never do full compactions? So I am not convinced that 1 is an 
> appropriate value.
>
> Also, since the VM, up until now, has crashed if someone tried 
> -XX:MarkSweepAlwaysCompactCount=0 I think we can be sure that there 
> are no customers that are running with that setting. It should be safe 
> to forbid it.
>
> CR:
>
> 7110718 -XX:MarkSweepAlwaysCompactCount=0 crashes the JVM
> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7110718
>
> Thanks,
> Bengt