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

sangheon sangheon.kim at oracle.com
Fri Mar 18 17:28:21 UTC 2016

Hi Bengt,

Thanks for reviewing this.

On 03/18/2016 12:15 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::maxsize(). CR: https://bugs.openjdk.java.net/browse/JDK-8152118 Webrev: http://cr.openjdk.java.net/~sangheki/8152118/webrev.00/ I think this looks good. Thanks.

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. Right, we have this problem when we introduced range/constraint for command-line flags (JDK-8059557: JEP 245: Validate JVM Command-Line Flag Arguments). And adjusting the flag during argument processing was out-of-scope. (Non-goal: second item) Your opinion seems like adjusting related flags, am I correct? i.e. We set 'MinTLABSize' but the error happened related flags(YoungPLABSize and OldPLABSize). And then, I think it would be better to let the users set-up them because it will be hard to adjusting related flags. What extends we would decide candidate flags to adjust.

But I agree with you that it would be annoying for the users.

Thanks, Sangheon

Thanks, Bengt

Testing: JPRT, TestOptionsWithRanges.java for all platforms. Thanks, Sangheon

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