RFR (S): 8067438: Add test to verify minimal heap size

Bengt Rutisson bengt.rutisson at oracle.com
Thu Jan 8 08:17:27 UTC 2015


On 2015-01-08 09:09, Thomas Schatzl wrote:
> Hi,
>
> On Thu, 2015-01-08 at 08:44 +0100, Bengt Rutisson wrote:
>> On 2015-01-07 21:35, Thomas Schatzl wrote:
>>> Hi,
>>>
>>> On Wed, 2015-01-07 at 21:07 +0100, Bengt Rutisson wrote:
>>>> On 1/7/15 5:04 PM, Lindenmaier, Goetz wrote:
>>>>> Hi Bengt,
>>>>>
>>>>> I had to add the new path to this line:
>>>>>     * @library /testlibrary /testlibrary/whitebox  /../../test/lib
>>>> Right. I was using a repository that hadn't been updated to include this
>>>> change yet. Good that you noticed it and could handle it.
>>>>
>>>>> But then it works fine on the machine with 64K pages.
>>>> Great to hear! And my testing on our platforms also passed.
>>> Please add a comment about the 512 magic number in the test, and that we
>>> assume that the heap constraint of page size * 512 is at this time the
>>> largest heap sizing constraint. I.e. that this formula is a
>>> simplification of the actual calculation.
>>>
>>> Did you also test on a machine with large pages with parallel gc? Iirc
>>> there has been some constraint that e.g. parallel gc needs at least
>>> three (or four?) full pages for its heap, one for each of its spaces.
>>>
>>> So I am not sure if this test as is is sufficiently robust.
>> We don't use large pages for such small heaps. See this in
>> Arguments::finalize_vm_init_args():
>>
>>
>>     if (FLAG_IS_DEFAULT(UseLargePages) &&
>>         MaxHeapSize < LargePageHeapSizeThreshold) {
>>       // No need for large granularity pages w/small heaps.
>>       // Note that large pages are enabled/disabled for both the
>>       // Java heap and the code cache.
>>       FLAG_SET_DEFAULT(UseLargePages, false);
>>     }
>>
>> LargePageHeapSizeThreshold is 128 MB and since my test runs with -Xmx2m
>> (which admittedly can be aligned up to 32 mb) I think we will never use
>> large pages.
>>
>> But I'll do an explicit run on a large page enabled machine with
>> ParallelGC just to make sure.
> Okay :) But what if somebody sets -XX:+UseLargePages intentionally for a
> test run?
>
> Potentially we will need to exclude this case then.

Right. Maybe the easiest thing it to just add -XX:-UseLargePages to the 
@run command line. That overrides any arguments passed from JTreg.

Bengt

>
> Thanks,
>    Thomas
>
>



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