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

[Derek White]

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
>