RFR(s): 8152188: Allow CMSBitMapYieldQuantum for BitMap::clear_range and clear_large_range

[Jon Masamitsu]

http://cr.openjdk.java.net/~sangheki/8152188/webrev.00/src/share/vm/runtime/commandLineFlagConstraintsGC.cpp.udiff.html

I would expand the message so that the user understands that the
size depends on the heap size.

+ CommandLineError::print(verbose,
+ "CMSBitMapYieldQuantum (" SIZE_FORMAT ") must "
+ "be less than or equal to bitmap size (" SIZE_FORMAT ") " whose size 
corresponds to the size of old generation of the Java heap\n",
+ value, bitmap_size);


The rest looks good.

Jon

On 3/31/2016 4:37 PM, sangheon wrote:
> Hi all,
>
> Could I have a couple of reviews for this change?
>
> CMSBitMapYieldQuantum can be changed by command-line and different 
> values on this flag result in different ranges at BitMap when we clear 
> the bitmap by BitMap::clear_large_range(). And if we can't satisfy the 
> criteria for 'large' range of '32', we will face an assert from 
> BitMap::clear_large_range().
> As we already have clear_range(), it would be better to call it 
> instead of firing an assert.
> If we change to use 'clear_range()' will resolve the problem as well, 
> but I didn't want to change like that which would result in 
> performance regression.
> In addition, we need a constraint to limit its maximum not to exceed 
> the mark bitmap size.
>
> CR: https://bugs.openjdk.java.net/browse/JDK-8152188
> Webrev: http://cr.openjdk.java.net/~sangheki/8152188/webrev.00
> Testing: JPRT, runtime/commandline JTREG tests for all platforms.
>
> Thanks,
> Sangheon
>