RFR (XS) 8204966: [TESTBUG] hotspot/test/compiler/whitebox/IsMethodCompilableTest.java test fails with -XX:CompileThreshold=1

[David Buck]

Hi Vlad!

Thanks for looking at this change!

 > You can hit some strange behavior if COMPILE_THRESHOLD very different
 > from BACKEDGE_THRESHOLD.

I'm not sure I understand. Do you mean that the these tests behave 
strangely? These values are only impacting the number of invocations / 
loop iterations these tests do to try and force HotSpot to compile 
something. As long as we do enough invocations/iterations, I can't 
imagine any weird behavior from the tests themselves.

 > I would suggest set max for COMPILE_THRESHOLD instead and leave
 > BACKEDGE_THRESHOLD calculation the same.

You mean set a min (not max), right? The problem is the test was not 
doing enough iterations, not too many. Anyway, in this code 
COMPILE_THRESHOLD only seems to be used to represent what the JVM is set 
for. (i.e. it is only used to (help) calculate THRESHOLD and 
BACKEDGE_THRESHOLD).

We *could* do something like this:

===
      static {
          if (TIERED_COMPILATION) {
              BACKEDGE_THRESHOLD = THRESHOLD = 150000;
          } else {
-             THRESHOLD = COMPILE_THRESHOLD;
+             THRESHOLD = Math.max(10000, COMPILE_THRESHOLD);
-             BACKEDGE_THRESHOLD = COMPILE_THRESHOLD *
- Long.parseLong(getVMOption("OnStackReplacePercentage"));
+             BACKEDGE_THRESHOLD = THRESHOLD *
+ Long.parseLong(getVMOption("OnStackReplacePercentage"));
          }
      }

===

But I'm not sure I see how the above is necessarily an improvement 
unless we suspect the test cases are also not doing enough invocations 
to trigger normal JIT as in addition to the OSR failure in jdk-8204966. 
If that is the case, maybe we should just scrap the entire if block and 
just go with something like this:

===
      static {
          BACKEDGE_THRESHOLD = THRESHOLD = 150000;
      }
===


Cheers,
-Buck


On 2018/08/05 4:04, Vladimir Kozlov wrote:
> You can hit some strange behavior if COMPILE_THRESHOLD very different 
> from BACKEDGE_THRESHOLD.
> I would suggest set max for COMPILE_THRESHOLD instead and leave 
> BACKEDGE_THRESHOLD calculation the same.
> 
> Thanks,
> Vladimir
> 
> On 8/4/18 4:26 AM, David Buck wrote:
>> Hi!
>>
>> May I please get a review of this trivial fix to a testcase.
>>
>> bug report:
>> https://bugs.openjdk.java.net/browse/JDK-8204966
>>
>> webrev
>> http://cr.openjdk.java.net/~dbuck/8204966.0/
>>
>> Cheers,
>> -Buck