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

Thomas Schatzl thomas.schatzl at oracle.com
Mon Jan 9 14:38:46 UTC 2017


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.

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.


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