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

Jon Masamitsu jon.masamitsu at oracle.com
Tue Jul 7 04:05:51 UTC 2015


Sangheon,

Send me the updated patch and I'll integrate it.

Jon

On 7/6/2015 2:44 PM, sangheon.kim wrote:
> 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
>>
>



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