RFR: JDK-8148759: G1AllocRegion::_count inconsistently used if more than one context is active

Stefan Johansson stefan.johansson at oracle.com
Fri Mar 18 09:39:50 UTC 2016


Looks good,

Thanks for fixing this,
Stefan

On 2016-03-17 18:04, Bengt Rutisson wrote:
>
> Hi everyone,
>
> Could I have a couple of reviews for this change?
>
> http://cr.openjdk.java.net/~brutisso/8148759/webrev.00
> https://bugs.openjdk.java.net/browse/JDK-8148759
>
> The _count value is per G1GCAllocRegion, so if we have more than one 
> survivor alloc region we will notice too late that we have exceeded 
> the maximum number of regions we had decided to use for survivors.
>
> The proposed patch uses young_list()->survivor_length() instead, which 
> is a "global" value for all alloc regions. This value used to be 
> updated when we retired a region, but to make proper use of it it 
> needs to be updated when we pick a new survivor region. Thus, I had to 
> move the call to young_list()->add_survivor_region(). I've gone 
> through and checked other users of the values updated by 
> add_survivor_region() and I haven't found anyone that is using this 
> value inside of the actual evacuation path, which is where the 
> difference would be noticeable.
>
> Thanks,
> Bengt



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