RFR (S): 8079555: REDO - Determining the desired PLAB size adjusts to the the number of threads at the wrong place

[sangheon.kim]

Hi Jon,

Thanks for reviewing this.
And I need a sponsor for this change.
Would you sponsor this?

Thanks,
Sangheon


On 07/06/2015 02:18 PM, Jon Masamitsu wrote:
> Sangheon,
>
> Changes look good.
>
> Jon
>
>
> On 06/05/2015 03:34 PM, sangheon.kim wrote:
>> Hi all,
>>
>> Please review this REDO change to determine the desired PLAB size for 
>> current gc worker threads.
>> The reason for back out of previous 
>> change(https://bugs.openjdk.java.net/browse/JDK-8073204) was it 
>> wouldn't guarantee to be '>= PLAB minimum size'. So added 
>> MAX2(min_size(),) to guarantee that.
>>
>> Currently we calculate an optimal PLAB size with current number of gc 
>> workers.
>> When the number of workers changes dynamically 
>> (-XX:+UseDynamicNumberOfGCThreads), the desired PLAB size returned(by 
>> desired_plab_sz()) is still tuned to the number of gc workers that 
>> has been used previously.
>>
>> This change is, firstly calculate the desired PLAB value for a single 
>> gc worker and then return desired PLAB size which is bigger(or equal) 
>> than PLAB min size according to the current number of threads.
>>
>> CR:
>> https://bugs.openjdk.java.net/browse/JDK-8079555
>>
>> Webrev:
>> http://cr.openjdk.java.net/~sangheki/8079555/webrev.00/
>>
>> Test:
>> JPRT
>>
>> Thanks,
>> Sangheon
>