Fwd: RFR (XXS): 8169643: [TESTBUG] GCBasher test fails with G1, CMS and Serial.

Dmitry Fazunenko dmitry.fazunenko at oracle.com
Tue Jan 10 16:09:35 UTC 2017

Hi Thomas,

On 09.01.2017 17:38, Thomas Schatzl wrote:
> Hi,
> On Mon, 2017-01-09 at 16:50 +0300, Dmitry Fazunenko wrote:
>> Hi in the new year!
>> I got off line comment from Igor I. that  Xmx is not needed here at
>> all.
>> And I agree with Igor.
>> GCBasher test was written many years ago, probably in those times
>> when default maximum heap size was 64MB.
>> So, specifying Xmx was necessary to increase heap to allocate such a
>> big structure.
>> Nowadays, it's hard to find a host where maximum heap size set by the
>> ergonomics will be less than 256MB.
>> GCBasher doesn't try to allocate all available memory, it just
>> allocates a big structure several time.
>> So, I think -Xmx option could be removed from this test:
>> http://cr.openjdk.java.net/~dfazunen/8169643/webrev.02/
>> Tested by RBT with and without -XX:-UseCompressedOpps
>    I think the limitation has been introduced so that gcbasher does
> something useful, i.e. execute enough GCs. With a multi-GB heap at its
> disposal, I expect that the amount of GCs executed will be
> significantly lower than it is now.

Your arguments do certainly make sense.
> I prefer to have a 256M limit to none; and maybe the test could be run
> once with and without UseCompressedOops with appropriate heap sizes
> instead if there is enough cpu time in our testing infrastructure.
I suggest to start with original version of the fix:
(+ copyright updates)

and submit an RFE to limit max heap size depending of UseCompressedOops 
Such RFE could implemented much easily after integration of
     JDK-8172417 Verundy: Library to simplify using TestNG for Hotspot 
test development
Now it's a bit tricky to get known from the test the values of external 

Are you okay with that?


> Thanks,
>    Thomas

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