RFR(XXS) 8187629: NMT: Memory miscounting in compiler (C2)

[Vladimir Kozlov]

On 9/19/17 9:36 AM, Zhengyu Gu wrote:
> Hi Vladimir,
> 
> 
> On 09/19/2017 12:14 PM, Vladimir Kozlov wrote:
>> Compilers also use a lot thread local ResourceArea - 
>> Thread::current()->resource_area() and NEW_RESOURCE_ARRAY() macro.
>> But thread local area is defined as mtThread:
>>
>> http://hg.openjdk.java.net/jdk10/hs/hotspot/file/5ab7a67bc155/src/share/vm/runtime/thread.cpp#l218 
> 
> 
> Thread's resource area is general purpose per-thread storage and used by 
> many subsystems. Unfortunately, NMT has no way to distinguish the users 
> at this moment, categorizing as mThread is sort of placeholder.
> 
> I am welcome to any suggestions

Thread() is called from CompilerThread() and we can pass a parameter to 
indicate user. Or add a virtual method to Thread class to check type of 
thread.

In the past we had compiler local changes to get information how much 
memory was used during compilation but it was never get pushed. We 
accessed Arena::_bytes_allocated for that.

Thanks,
Vladimir

> 
> Thanks,
> 
> -Zhengyu
> 
> 
>>
>>
>> Vladimir
>>
>> On 9/18/17 12:17 PM, Zhengyu Gu wrote:
>>> Compiler (C2) uses ResourceArea instead of Arena in some 
>>> circumstances, so it can take advantage of ResourceMark. However, 
>>> ResourceArea is tagged as mtThread, that results those memory is 
>>> miscounted by NMT
>>>
>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8187629
>>> Webrev: http://cr.openjdk.java.net/~zgu/8187629/webrev.00/
>>>
>>>
>>> Test:
>>>
>>>    hotspot_tier1 (fastdebug and release) on Linux x64
>>>
>>>
>>> Thanks,
>>>
>>> -Zhengyu