RFR: 8241828: JFR: Some streaming tests require a larger heap size with ZGC

[Stefan Karlsson]

Did some extra testing on TestChunkGap and G1:

With compressed oops:
-Xmx300m : OOME
-Xmx350m : Barely passes

Without compressed oops:
-Xmx450m : OOME
-Xmx500m : Passes

I issued a 'jcmd GC.class_histogram' in the middle of the run and got:

  num     #instances         #bytes  class name (module)
-------------------------------------------------------
    1:       2473067      158635784  [Ljava.lang.Object; 
(java.base at 15-internal)
    2:       2463224      118234752  jdk.jfr.consumer.RecordedEvent 
(jdk.jfr at 15-internal)
    3:       4894598      117470352  java.lang.Integer 
(java.base at 15-internal)
    4:           157       39960680  [Ljdk.jfr.consumer.RecordedEvent; 
(jdk.jfr at 15-internal)
    5:        369731       18447144  [B (java.base at 15-internal)
    6:        368815       11802080  java.lang.String 
(java.base at 15-internal)
    7:           331         584344  [I (java.base at 15-internal)
...

Does this look right?

StefanK

On 2020-03-30 22:03, Erik Gahlin wrote:
> Seems strange that the test would require over 512 MB. I would expect 
> the TestChunkGap not to use a live set of more than 25 MB. The test only 
> emits three events.
> 
> TestFilledChunks is easier to understand as it may emit millions of 
> events. Still it must be a bug in JFR then, because it should not keep 
> them around.
> 
> Erik
> 
>> On 30 Mar 2020, at 19:24, mikhailo.seledtsov at oracle.com 
>> <mailto:mikhailo.seledtsov at oracle.com> wrote:
>>
>> Hi Stefan,
>>
>> I would recommend adding "@requires os.maxMemory > " to the test, to 
>> make sure that test does not execute on a host/node that does not have 
>> sufficient memory. E.g. "@requires os.maxMemory > 1G"
>>
>> Otherwise the change looks good to me.
>>
>>
>> Thanks,
>>
>> Misha
>>
>> On 3/30/20 4:07 AM, Stefan Karlsson wrote:
>>> Hi all,
>>>
>>> Please review this small patch to increase the max heap size of a 
>>> couple of JFR streaming tests.
>>>
>>> https://cr.openjdk.java.net/~stefank/8241828/webrev.01/
>>> https://bugs.openjdk.java.net/browse/JDK-8241828
>>>
>>> The default heap size is 512m when these tests are run. G1 uses 
>>> almost 500m, but ZGC needs a bit more. I propose that we set the max 
>>> heap size to 768m.
>>>
>>> Thanks,
>>> StefanK
>