RFR: 8202591: Remove usage of CMSEdenChunksRecordAlways in defNewGeneration.cpp

[Stefan Karlsson]

On 2018-05-04 21:04, Kim Barrett wrote:
>> On May 4, 2018, at 4:58 AM, Stefan Karlsson <stefan.karlsson at oracle.com> wrote:
>>
>> Hi all,
>>
>> Please review this patch to remove the usage of CMSEdenChunksRecordAlways in defNewGeneration.cpp.
>>
>> http://cr.openjdk.java.net/~stefank/8202591/webrev.01/
>> https://bugs.openjdk.java.net/browse/JDK-8202591
> 
> Looks good.  Thanks for the detailed description below.

Thanks for reviewing.

StefanK

> 
>> This is a step towards getting rid of CMS dependent code from defNewGeneration.cpp.
>>
>> DefNewGeneration::allocate and DefNewGeneration::par_allocate both have this code:
>>
>> #if INCLUDE_ALL_GCS
>> if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
>>     if (_old_gen != NULL) {
>>        _old_gen->sample_eden_chunk();
>>      }
>> #endif
>>
>> _old_gen is TenuredGeneration when running with Serial, which uses the default sample_eden_chunk() implementation in Generation:
>>   virtual void sample_eden_chunk() {}
>>
>> _old_gen is ConcurrentMarkSweepGeneration when running with CMS, which uses:
>>   void sample_eden_chunk() {
>>     //Delegate to collector
>>     return collector()->sample_eden_chunk();
>>   }
>>
>> and this is the code in CMSCollector's sample_eden_chunk:
>> void CMSCollector::sample_eden_chunk() {
>>   if (CMSEdenChunksRecordAlways && _eden_chunk_array != NULL) {
>>
>> Note also that CMSEdenChunksRecordAlways is always true, even when we're not running with CMS.
>>
>> I propose that we get rid of the CMSEdenChunksRecordAlways check in defNewGeneration.cpp.
>>
>> Thanks,
>> StefanK
> 
>