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

sangheon.kim sangheon.kim at oracle.com
Tue Jun 23 23:15:43 UTC 2015

Hi Thomas,

Thank you for reviewing this.
As we discussed from another email, nightly tests were okay.


On 06/08/2015 03:33 AM, Thomas Schatzl wrote:
> Hi Sangheon,
> On Fri, 2015-06-05 at 15:34 -0700, 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:
>    looks okay. Can you do a nightly run with the changes in Aurora too,
> just in case?
> Thanks,
>    Thomas

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