RFR (XS): 8216316: jdk/jfr/event/gc/detailed/TestPromotionEventWithG1.java fails due to reserved TLAB area too large

[Lindenmaier, Goetz]

Hi Thomas, 

all our test passed with your patch.

But I found a similar issue: 
TestVerifyStackAfterDeopt.java says:
MinTLABSize (1024) must be greater than or equal to reserved area in TLAB (1280)

and the fix is:
--- a/test/hotspot/jtreg/compiler/interpreter/TestVerifyStackAfterDeopt.java	Mon Jan 07 15:49:31 2019 +0100
+++ b/test/hotspot/jtreg/compiler/interpreter/TestVerifyStackAfterDeopt.java	Tue Jan 08 17:03:19 2019 +0100
@@ -28,6 +28,7 @@
  * @bug 8209825
  * @summary Checks VerifyStack after deoptimization of array allocation slow call
  * @run main/othervm -XX:+IgnoreUnrecognizedVMOptions -XX:TieredStopAtLevel=1
+ *                   -XX:AllocatePrefetchLines=1 -XX:AllocateInstancePrefetchLines=1 -XX:AllocatePrefetchStepSize=16 -XX:AllocatePrefetchDistance=1
  *                   -XX:MinTLABSize=1k -XX:TLABSize=1k
  *                   -XX:+DeoptimizeALot -XX:+VerifyStack
  *                   compiler.interpreter.TestVerifyStackAfterDeopt

Do you think this should be included in your fix right away?
Else I would make an extra bug.

Best regards,
  Goetz.


> -----Original Message-----
> From: Thomas Schatzl <thomas.schatzl at oracle.com>
> Sent: Dienstag, 8. Januar 2019 13:42
> To: hotspot-gc-dev at openjdk.java.net
> Cc: Lindenmaier, Goetz <goetz.lindenmaier at sap.com>
> Subject: RFR (XS): 8216316:
> jdk/jfr/event/gc/detailed/TestPromotionEventWithG1.java fails due to
> reserved TLAB area too large
> 
> Hi all,
> 
>   can I have reviews for this fix to some test options to make the
> TestPromotionEventWithG1 test more stable on the platforms we support?
> 
> In particular, depending on hardware, the minimum TLAB size given in
> the test was too small to accomodate the prefetching code C2 emits when
> allocating objects.
> 
> The fix is to minimize this buffer by twiddling with prefetching
> amounts, and increasing the minimum tlab size a bit - so that the test
> still fails with the patch for 8212766 not applied.
> 
> Thanks go to Goetz from SAP who figured out the values for the
> prefetching so that most supported systems worked.
> 
> @Goeth: can you check this fix on your systems too?
> 
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8216316
> Webrev:
> http://cr.openjdk.java.net/~tschatzl/8216316/
> Testing:
> Test failing test on various machines in our CI system
> 
> Thanks,
>   Thomas
>