Review quest for JDK-7067973: test/java/lang/management/MemoryMXBean/ hanging intermittently

Leonid Mesnik leonid.mesnik at
Thu Nov 28 02:16:33 PST 2013

Eric, Mandy

Sorry that I looping on very late step. It is not a review just suggestion.
We have whitebox API in Hotspot which includes fullGC() method. It could 
be used to reliably provoke full GC.
See example in

Should such approach works for you?

Also please note that your new variant of test fails if any of GC is set 
explicitly. It is incompatible with GC setting.
We set GC's and GC-related options during Promotion/Nightly/PIT in 
Hotspot/SVC. For us is better if test just works
with any GC set externally.

Do you need to run it with all GC each time?

On 11/28/2013 09:21 AM, Eric Wang wrote:
> Hi Mandy,
> Yes, I have tested and all settings are passed, as you mentioned the 
> test hangs with -XX:+UseG1GC -XX:+ExplicitGCInvokesConcurrent and 
> default heap size as no GC happens on Old Gen. That is why to add 
> -Xmx2m and big object to make sure GC happens.
> I didn't realized the -Xconcgc is same as -XX:+UseConcMarkSweepGC, i 
> have updated the webrev:
> <>
> Thanks,
> Eric
> On 2013/11/27 10:17, Mandy Chung wrote:
>> Hi Eric,
>> I'll defer this to the serviceability team to sponsor it and also get 
>> one more review.
>> I don't think you need all 7 @runs.  -Xconcgc is equivalent to 
>> setting -XX:+UseConcMarkSweepGC. For G1 and CMS, you should use 
>> -XX:+ExplicitGCInvokesConcurrent so that System.gc will force a GC in 
>> foreground that you can count the GC reliably. The test wants to get 
>> notified for each System.gc and if there is any GC caused by 
>> allocation failure, the test would fail due to the unexpected GC 
>> count.  It seems that you may run into this issue setting -Xmx2m.
>> Have you got the test passed in all settings?   I'm seeing that the 
>> test hangs with -XX:+UseG1GC -XX:+ExplicitGCInvokesConcurrent without 
>> -Xmx2m.  Looks like there is no GC in the old gen - I'm not familiar 
>> with G1 if it allocates the big object in the old gen.  Jarolsav - 
>> can you help Eric diagnose this issue?  I recalled you ran into 
>> something like that before - maybe Staffan?
>> thanks
>> Mandy
>> On 11/25/2013 8:53 PM, Eric Wang wrote:
>>> Hi Mandy,
>>> 1. for L34-40, executing tests with 7 settings is trying to cover 
>>> more cases (normal cases and special cases), especially last 3 
>>> settings, as found that the test hung if using vm option 
>>> "-XX:+ExplicitGCInvokesConcurrent" with one of 3 options 
>>> -XX:+UseG1GC, -XX:+UseConcMarkSweepGC or -Xconcgc
>>> 2. for L61, that is right, the test has been updated. please review.
>>> <>
>>> Thanks,
>>> Eric
>>> On 2013/11/26 8:37, Mandy Chung wrote:
>>>> Hi Eric,
>>>> On 11/24/2013 7:41 PM, Eric Wang wrote:
>>>>> Hi Mandy & All,
>>>>> Sorry for late!
>>>>> The webrev below is just finished based on the comments from 
>>>>> peers, please help to review.
>>>>> <>
>>>> Thanks for the patch that looks okay.  Some comments:
>>>> L34-40: can you explain why you want to run all 7 settings? I would 
>>>> expect one for each collector.
>>>> L61: I think the static checker variable is meant to be a local 
>>>> variable (and looks like "pools" and "managers" don't need to be 
>>>> static variable).
>>>> Mandy
>>>>> Thanks,
>>>>> Eric
>>>>> On 2013/11/15 10:55, Mandy Chung wrote:
>>>>>> Hi Eric,
>>>>>> On 11/14/2013 6:16 PM, Eric Wang wrote:
>>>>>>> Hi Everyone,
>>>>>>> I'm working on the bug 
>>>>>>> It is a test bug as the test doesn't guarantee memory allocated 
>>>>>>> from the Old Gen, if the used memory is zero and doesn't cross 
>>>>>>> the threshold, no notification is sent, so both the main thread 
>>>>>>> and Checker thread are blocked to wait for the GC notification.
>>>>>>> so the suggested fix is similar as the fix 
>>>>>>> <> to 
>>>>>>> create big object to make sure the old gen usage crosses the 
>>>>>>> threshold and run test with different GC vmoptions.
>>>>>> What are you looking for specifically?  I have provided the above 
>>>>>> information.  I need to see the webrev to provide further feedback.
>>>>>> Mandy

Leonid Mesnik

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