RFR: 8080877: Don't use workers()->total_workers() when walking G1CollectedHeap::_task_queues

[Derek White]

Looks good to me!

  - Derek

On 5/22/15 8:17 AM, Stefan Karlsson wrote:
> Hi all,
>
> The _task_queues are initialized to contain ParallelGCThreads number 
> of queues:
>
>   int n_queues = (int)ParallelGCThreads;
>   _task_queues = new RefToScanQueueSet(n_queues);
>
> When iterating over the queues we use workers()->total_workers() to 
> determine the number of queues in the set:
>
>   const uint n = workers()->total_workers();
>   for (uint i = 0; i < n; ++i) {
>     task_queue(i)->stats.reset();
>   }
>
> which gives the same result, since the workers are also initialized 
> with ParallelGCThreads:
>
>   _workers = new FlexibleWorkGang("GC Thread", ParallelGCThreads,
>                           /* are_GC_task_threads */true,
>                           /* are_ConcurrentGC_threads */false);
>   _workers->initialize_workers();
>
> I propose that we change the iteration code to ask the task queue set 
> how many task queues it contain:
>
> -  const uint n = workers()->total_workers();
> +  const uint n = num_task_queues();
>    for (uint i = 0; i < n; ++i) {
>      task_queue(i)->stats.reset();
>    }
>
> I also removed the unnecessary forward declarations of OopTaskQueue 
> and OopTaskQueueSet. This isn't strictly needed for this patch, but 
> was causing problems while I was prototyping this and other patches.
>
> http://cr.openjdk.java.net/~stefank/8080877/webrev.00/
> https://bugs.openjdk.java.net/browse/JDK-8080877
>
> Thanks,
> StefanK