RFR(xs): 8152118: MinTLABSize should be less than TLAB max

sangheon sangheon.kim at oracle.com
Fri Mar 18 18:02:15 UTC 2016


Hi Derek,

Thanks for reviewing this!

Sangheon


On 03/18/2016 10:52 AM, Derek White wrote:
> Hi Sangheon ,
>
> Looks good!
>
>  - Derek
>
> On 3/18/16 3:15 AM, Bengt Rutisson wrote:
>>
>> Hi Sangheon,
>>
>> On 2016-03-18 06:43, sangheon wrote:
>>> Hi all,
>>>
>>> Could I have a couple of reviews for this tiny change?
>>>
>>> MinTLABSize doesn't have upper limit now and this change is 
>>> proposing to be less than or equal to 
>>> ThreadLocallAllocBuffer::max_size().
>>>
>>> CR: https://bugs.openjdk.java.net/browse/JDK-8152118
>>> Webrev: http://cr.openjdk.java.net/~sangheki/8152118/webrev.00/
>>
>> I think this looks good.
>>
>> However, I have a related question. When I set up the min tlab size 
>> high I get some issues reported from other constraint functions:
>>
>> $ java  -XX:MinTLABSize=16m -XX:G1HeapRegionSize=32m -version
>> YoungPLABSize (4096) must be greater than or equal to ergonomic PLAB 
>> minimum size (2097152)
>> OldPLABSize (1024) must be greater than or equal to ergonomic PLAB 
>> minimum size (2097152)
>> Error: Could not create the Java Virtual Machine.
>> Error: A fatal exception has occurred. Program will exit.
>>
>> I don't think this is a problem with the patch that you are proposing 
>> now, but I thought I should mention it. Do you think this is 
>> something we would like to fix in the argument parsing (like 
>> adjusting the PLAB max to be at least PLAB min) or should we just let 
>> the users set up the PLAB sizes if they use large TLAB sizes?
>>
>> This is a pre-exiting problem. Even without your patch I get the same 
>> behavior. So, you can consider your proposed patched reviewed.
>>
>> Thanks,
>> Bengt
>>
>>
>>> Testing: JPRT, TestOptionsWithRanges.java for all platforms.
>>>
>>> Thanks,
>>> Sangheon
>>
>



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