FW: RFR(S): 8130434: [TESTBUG] Harden TestLargePageUseForAuxMemory for more page size combinations.

[Thomas Schatzl]

Hi Goetz,

  sorry for taking a while to pick this up...

On Fri, 2015-07-17 at 09:52 +0000, Lindenmaier, Goetz wrote:
> Hi,
>  
> could I please get a review for this change?  I also please need a
> sponsor.

I can sponsor the change.

> I posted to hotspot-dev before, gc-dev is probably better.
>
> This change is crafted on top of “8079208:
> gc/g1/TestLargePageUseForAuxMemory.java fails due to not considering
> page allocation granularity for setup”.
>  
> From: Lindenmaier, Goetz 
> Sent: Freitag, 10. Juli 2015 09:03
> To: hotspot-dev at openjdk.java.net
> Subject: RFR(S): 8130434: [TESTBUG] Harden
> TestLargePageUseForAuxMemory for more page size combinations.
>  
> Hi,
>  
> this test wants to enforce large page usage for the card table etc.
> It fails for certain page sizes we see on ppc, linux and aix.
>  
> On some, large page size == page size holds and this test fails: 
> "To test we would require to use an invalid heap size (assert failed:
> 33554432 > 33554432)" 
> Fix: Just skip the test in this case as it's pointless. 

Okay, I can understand that change.

> We have a machine with page size = 64K and large page size 4M. 
> In this case heapSizeDiffForBitmap was too small to reduce the heap
> size. 
> Due to the big value for the normal page size heap alignment is >
> largePageSize 
> and the heap size was aligned up to the original value. 
> Error: "'G1 'Prev Bitmap': pg_sz=65536' missing from stdout/stderr" 
> Fix: consider heap alignement for heapSizeDiffForBitmap.

I am possibly missing something here:

So page size is 64k, large page size 4M.

In this case, heapSizeForBitmapUsingLargePages = 4M * 64 = 256M, and
heapSizeDiffForBitmap is (assuming allocGranularity = page size = 64k), 

  max(4M (=64k * 64), 1M, 4M)

= 4M, which does not seem to be an issue?

Further, the use of lcm indicates that the actual reason is that in some
of your setups, small-page-size * card size > largePageSize? It is
possible, so this is just another try to make the test more robust?

The change seems good to me.

Thanks,
  Thomas