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

[Bengt Rutisson]

Jon,

Thanks for the review!

On 2011-11-14 18:38, Jon Masamitsu wrote:
> Bengt,
>
> The change looks fine.  Did you consider making 
> MarkSweepAlwaysCompactCount
> unsigned?

Good point. I'll change to unsigned.

Bengt

>
> 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