[RFR] 8043766: CMM Testing: 8u40 Decommit auxiliary data structures

[Andrey Zakharov]

On 26.09.2014 13:46, Thomas Schatzl wrote:
> Hi Andrey,
>
> On Thu, 2014-09-25 at 20:28 +0400, Andrey Zakharov wrote:
>> BTW, tested in aurora with latest jdk 8 updates
>> 593423.ute.hs_jtreg.accept.full
> Some questions:
>
> - the different tests seem to be only different in the number of
> iterations the allocate/link/mutate/deallocate cycle runs. They all use
> the same G1ConcRSLogCacheSize, but vary object alignment.
Different tests initiates Base class with different cache size number
     protected TestShrinkAuxiliaryData(int RSetCacheSize) {
         this.RSetCacheSize = RSetCacheSize;
     }

which then goes to:
vmOpts.add("-XX:G1ConcRSLogCacheSize=" + RSetCacheSize);

So tests runs with different options G1ConcRSLogCacheSize and 
ObjectAlignmentInBytes for non-32 bits systems

>
> That seems okay, but why is there need to run for different amount of
> time, particularly so many?
it runs DEFAULT_ITERATION_COUNT=1 for now
>
> Earlier versions of the test varied G1ConcRSLogCacheSize and object
> alignment, and did only a single iteration always. Not sure if simply
> testing G1ConcRSLogCacheSize for a few important values (0, 10, 15,
> maybe not even the last because the only difference in code is for 0 and
> something) and a single fixed length (not necessarily a single
> iteration) would achieve the same job?
>
> G1ConcRSLogCacheSize of 10 does not require that much memory (and in
> fact is default) so that you need to worry about its maximum size.
I'm worried about 2^23 - 2^30 caches size which can brings massive 
swapping and timeouts of tests
>
> - fixing G1ConcRSLogCacheSize would also remove the need to calculate
> some maximum value for G1ConcRSLogCacheSize. GetMaxCacheSize()
> calculates the maximum G1ConcRSLogCacheSize based on the free java heap.
> However, the data structure is allocated on the C heap, there is no real
> connection between free java heap and free C heap anyway.
Could please, suggest something here?
I'm just judging about available memory by available heap memory.
Thanks.
>
> Thanks,
>    Thomas
>
>