RFR: 8080869: FlexibleWorkGang initializes _active_workers to more than _total_workers

[Stefan Karlsson]

On 2015-05-21 19:43, Jon Masamitsu wrote:
> Change looks good.  Reviewed.

Thanks.

StefanK

>
> Jon
>
> On 05/21/2015 05:28 AM, Stefan Karlsson wrote:
>> Hi all,
>>
>> Please, review this small patch to fix the initialization of 
>> FlexibleWorkGang::_active_workers.
>>
>> http://cr.openjdk.java.net/~stefank/8080869/webrev.00/
>> https://bugs.openjdk.java.net/browse/JDK-8080869
>>
>> From the bug report:
>> -------------------------------------------------------------------------------- 
>>
>> This is the FlexibleWorkGang constructor:
>>
>>   FlexibleWorkGang(const char* name, uint workers,
>>                    bool are_GC_task_threads,
>>                    bool  are_ConcurrentGC_threads) :
>>     WorkGang(name, workers, are_GC_task_threads, 
>> are_ConcurrentGC_threads),
>>     _active_workers(UseDynamicNumberOfGCThreads ? 1U : 
>> ParallelGCThreads) {}
>>
>> and the WorkGang constructor:
>>
>> WorkGang::WorkGang(const char* name,
>>                    uint        workers,
>>                    bool        are_GC_task_threads,
>>                    bool        are_ConcurrentGC_threads) :
>>   AbstractWorkGang(name, are_GC_task_threads, 
>> are_ConcurrentGC_threads) {
>>   _total_workers = workers;
>> }
>>
>> If 'workers' are less than ParallelGCThreads, then _active_workers 
>> will be set to a value that is greater than _total_workers (unless we 
>> run with UseDynamicNumberOfGCThreads). Both G1 and CMS typically sets 
>> the number of concurrent workers to a value below ParallelGCThreads.
>>
>> This is currently a benign bug, since the GCs will later calculate a 
>> new value for _active_workers that will never be higher than 
>> _total_workers.
>>
>> However, this bug impedes stricter asserts and should be fixed.
>> -------------------------------------------------------------------------------- 
>>
>>
>> Thanks,
>> StefanK
>