CRR (S): 7119027: G1: use atomics to update RS length / predict time of inc CSet

[Tony Printezis]

Thanks Igor! All set thanks to Igor and Bengt.

Tony

On 12/20/2011 06:22 PM, Igor Veresov wrote:
> Looks good.
>
> igor
>
>
> On Tuesday, December 20, 2011 at 9:52 AM, Tony Printezis wrote:
>
>> Hi all,
>>
>> I'd like a couple of code reviews for this small change that resolves
>> the race that we identified a few weeks ago (and which we already guard
>> against in the code):
>>
>> http://cr.openjdk.java.net/~tonyp/7119027/webrev.0/
>>
>> Instead of using atomics I decided to take an alternative approach to
>> eliminate the race which as described in the CR:
>>
>> "The final fix is somewhat different to what I had originally planned
>> and does not use atomics. The observation is that only two threads can
>> update the fields in question: a mutator thread that retires a region
>> before allocating a new one (and it has to take the Heap_lock in order
>> to do so - so those updates are serialized anyway) and a concurrent
>> refinement thread that samples the RSets in the inc CSet. What we'll do
>> is to accumulate the updates from each thread on separate fields and
>> we'll just combine them at the start of a GC."
>>
>> Thanks,
>>
>> Tony
>