RFR (XXS): 8164133: Tests gc/arguments/TestAlignmentToUseLargePages.java and gc/cms/TestBubbleUpRef.java use too small heap

sangheon sangheon.kim at oracle.com
Mon Aug 22 23:30:34 UTC 2016


Hi Jon,

On 08/22/2016 02:55 PM, Jon Masamitsu wrote:
>
>
> On 08/22/2016 12:49 PM, sangheon wrote:
>> Hi Dima and Jon,
>>
>> Let me interrupt a little bit.
>>
>> As you know, we can have quite big heap alignment with large pages 
>> enabled. And this affects to our heap ergonomics.
>> However, as the test case tests only whether the VM is successfully 
>> initialized or not, I think large 'Xms' option is enough to fix the 
>> problem.
>> For me, the new 'Xms/Xmx' values seem always OK to initialize VM.
>>
>> Jon, the original test failure contains '-Xms7m -Xmx9m' options.
>> "GC triggered before VM initialization completed. Try increasing 
>> NewSize, current value 1280K. "
>
> If I execute "java -XX:+PrintGCDetails -XX:+UseConcMarkSweepGC -Xms7m 
> -Xmx9m -XX:+UseLargePages -version"
>
> I see
>
> [0.165s][info   ][gc,heap,exit ] Heap
> [0.165s][info   ][gc,heap,exit ]  par new generation   total 2432K, 
> used 1679K [0x00000000ff600000, 0x00000000ff8a0000, 0x00000000ff8a0000)
> [0.165s][info   ][gc,heap,exit ]   eden space 2176K,  77% used 
> [0x00000000ff600000, 0x00000000ff7a3d30, 0x00000000ff820000)
> [0.165s][info   ][gc,heap,exit ]   from space 256K,   0% used 
> [0x00000000ff820000, 0x00000000ff820000, 0x00000000ff860000)
> [0.165s][info   ][gc,heap,exit ]   to   space 256K,   0% used 
> [0x00000000ff860000, 0x00000000ff860000, 0x00000000ff8a0000)
> [0.165s][info   ][gc,heap,exit ]  concurrent mark-sweep generation 
> total 5504K, used 0K [0x00000000ff8a0000, 0x00000000ffe00000, 
> 0x0000000100000000)
>
> which says "par new generation   total 2432K" so isn't 2432K the 
> ParNew size?
In your log, you are right.
But I want to ask you whether you ran the above command on the same or 
similar host machine?

I got below message from same kind of machine.

$ java -Xlog:gc+heap=trace -Xms7M -Xmx9M -XX:+UseConcMarkSweepGC 
-XX:+UseLargePages -version

[0.004s][trace][gc,heap] CMS ergo set MaxNewSize: 0
[0.004s][trace][gc,heap] CMS set min_heap_size: 7340032 
initial_heap_size:  7340032 max_heap: 0
[0.020s][debug][gc,heap] Minimum heap 536870912  Initial heap 536870912  
Maximum heap 536870912
[0.020s][trace][gc,heap] 1: Minimum young 1310720 _*Initial young 
1310720*_  Maximum young 1310720
[0.020s][trace][gc,heap] Minimum old 65536  Initial old 535560192 
Maximum old 535560192
Java HotSpot(TM) 64-Bit Server VM warning: Failed to reserve shared 
memory. (error = 1)
[0.766s][debug][gc,heap] GC(0) Heap before GC invocations=0 (full 0):
[0.766s][debug][gc,heap] GC(0) *_par new generation   total 1152K_*, 
used 1024K [0x00000000e0000000, 0x00000000e0140000, 0x00000000e0140000)
[0.766s][debug][gc,heap] GC(0)   eden space 1024K, 100% used 
[0x00000000e0000000, 0x00000000e0100000, 0x00000000e0100000)
[0.766s][debug][gc,heap] GC(0)   from space 128K,   0% used 
[0x00000000e0100000, 0x00000000e0100000, 0x00000000e0120000)
[0.766s][debug][gc,heap] GC(0)   to   space 128K,   0% used 
[0x00000000e0120000, 0x00000000e0120000, 0x00000000e0140000)
[0.767s][debug][gc,heap] GC(0)  concurrent mark-sweep generation total 
523008K, used 0K [0x00000000e0140000, 0x0000000100000000, 
0x0000000100000000)
[0.767s][debug][gc,heap] GC(0)  Metaspace       used 3786K, capacity 
4480K, committed 4480K, reserved 1056768K
[0.767s][debug][gc,heap] GC(0)   class space    used 338K, capacity 
384K, committed 384K, reserved 1048576K
[0.798s][info ][gc,heap] GC(0) ParNew: 1024K->126K(1152K)
[0.799s][info ][gc,heap] GC(0) CMS: 0K->738K(523008K)
[0.799s][debug][gc,heap] GC(0) Heap after GC invocations=1 (full 0):
[0.799s][debug][gc,heap] GC(0)  par new generation   total 1152K, used 
126K [0x00000000e0000000, 0x00000000e0140000, 0x00000000e0140000)
[0.799s][debug][gc,heap] GC(0)   eden space 1024K,   0% used 
[0x00000000e0000000, 0x00000000e0000000, 0x00000000e0100000)
[0.799s][debug][gc,heap] GC(0)   from space 128K,  98% used 
[0x00000000e0120000, 0x00000000e013f9c8, 0x00000000e0140000)
[0.799s][debug][gc,heap] GC(0)   to   space 128K,   0% used 
[0x00000000e0100000, 0x00000000e0100000, 0x00000000e0120000)
[0.799s][debug][gc,heap] GC(0)  concurrent mark-sweep generation total 
523008K, used 738K [0x00000000e0140000, 0x0000000100000000, 
0x0000000100000000)

So the ParNew size is 1152K and the initial young size is 1280K(1310720) 
from my log.

FYI, the test machine has 524288 kB of huge page size and I think yours 
has different huge page size.

Thanks,
Sangheon


>
> Jon
>
>>
>> To answer to Jon's original question, the reason of "1280k (1310720)" 
>> is that NewSize(default value of 1363144) is aligned to gen 
>> alignment(65536) from GenCollectorPolicy::initialize_flags(). 
>> collectorPolicy.cpp:line 316
>> We resize NewSize from GenCollectorPolicy::initialize_size_info() if 
>> needed, but it seems like this is not the case.
>>
>> Given above, the patch seems okay.
>>
>> Thanks,
>> Sangheon
>>
>>
>> On 08/22/2016 10:37 AM, Jon Masamitsu wrote:
>>>
>>>
>>> On 08/22/2016 08:55 AM, Dmitry Fazunenko wrote:
>>>> Jon,
>>>>
>>>> The problem could be reproduced by the following command:
>>>>
>>>> #> java -Xmx3m -XX:+UseConcMarkSweepGC -XX:+AggressiveOpts -version
>>>> Error occurred during initialization of VM
>>>> GC triggered before VM initialization completed. Try increasing 
>>>> NewSize, current value 640K.
>>>
>>> I didn't notice that "-Xmx3m" was on the command line for the 
>>> original failure.
>>> Without -Xmx3m I expected that the default heap was large and 
>>> wondered why
>>> NewSize was so small.
>>>
>>> Jon
>>>
>>>>
>>>> increasing Xmx from 3m to 4m helps:
>>>>
>>>> #> java -Xmx4m -XX:+UseConcMarkSweepGC -XX:+AggressiveOpts -version
>>>> java version "9-ea"
>>>> Java(TM) SE Runtime Environment (build 9-ea+132)
>>>> Java HotSpot(TM) 64-Bit Server VM (build 9-ea+132, mixed mode)
>>>>
>>>> I don't see anything suspicious in the GC log (attached).
>>>>
>>>> There is no requirement to minimal heap required for Hotspot to 
>>>> work normally, so I think the tests should not start VM with so 
>>>> small heaps.
>>>>
>>>>
>>>> Thanks,
>>>> Dima
>>>>
>>>>
>>>>
>>>>
>>>> On 19.08.2016 21:02, Jon Masamitsu wrote:
>>>>> Dima,
>>>>>
>>>>> The error message I see in the logs is
>>>>>
>>>>> GC triggered before VM initialization completed. Try increasing 
>>>>> NewSize, current value 1280K.
>>>>>
>>>>> Do you know why the NewSize is so small?  I ask because I'm
>>>>> not sure setting a larger heap size will always fix this failure.
>>>>>
>>>>> If the test is run (with the parameters that fail) and 
>>>>> -Xlog:gc*=trace, you might
>>>>> see why the NewSize is so small (if you don't know now).
>>>>>
>>>>> Jon
>>>>>
>>>>>
>>>>> On 8/19/2016 9:02 AM, Dmitry Fazunenko wrote:
>>>>>> Hello,
>>>>>>
>>>>>> May I have to get a couple of reviews for a trivial fix:
>>>>>>
>>>>>> https://bugs.openjdk.java.net/browse/JDK-8164133
>>>>>> http://cr.openjdk.java.net/~dfazunen/8164133/webrev.01/
>>>>>>
>>>>>> Two tests set very small maximum heap size, which may cause:
>>>>>>   starts VM with too small heap size, which might cause
>>>>>>   Error occurred during initialization of VM
>>>>>> None of those tests does really require such a small heap, so 
>>>>>> just increasing should help.
>>>>>>
>>>>>> Thanks,
>>>>>> Dima
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>

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