Review Request: 8009298 and 8009777

[Zhengyu Gu]

Updated webrev based on Coleen and Dan's comment.

http://cr.openjdk.java.net/~zgu/8009298/webrev.01/


Thanks,

-Zhengyu

On 3/19/2013 11:23 AM, Daniel D. Daugherty wrote:
> The 2nd -> 4th lines will need a space before the final double-quote
> to print properly.
>
> Dan
>
>
> On 3/19/13 8:57 AM, Coleen Phillmore wrote:
>>
>> Zhengyu,
>> This looks good.   NIce documentation for the flag in globals.hpp. 
>> Can you reword slightly:
>>
>> +           "Automatically shutdown native memory tracking in stress 
>> "        \
>> +           "situations. When it is set to false, native memory 
>> tracking"      \
>> +           "will try its best to stay alive, even if it means that 
>> it has to" \
>> +           "sacrifice JVM 
>> performance")                                      \
>>
>>
>> Coleen
>>
>> On 3/11/2013 2:21 PM, Zhengyu Gu wrote:
>>> 8009298: NMT: Special version of class loading/unloading with 
>>> runThese stresses out NMT 
>>> <https://jbs.oracle.com/bugs/browse/JDK-8009298>
>>> 8009777: NMT: add new NMT dcmd to control auto shutdown option 
>>> <https://jbs.oracle.com/bugs/browse/JDK-8009777>
>>>
>>> The two are related. The change is to add an addition VM diagnostic 
>>> command-line option "AutoShutdownNMT".
>>>
>>> By default, native memory tracking runtime shuts itself down under 
>>> stress situation, and release memory to allow JVM continue running. 
>>> But this feature can be undesirable when this is the situation we 
>>> really want to know what's happening to JVM memory usage, even that 
>>> means that we need to sacrifice JVM performance.
>>>
>>> When AutoShutdownNMT is set to false, NMT will try its best to stay 
>>> alive by slowing down threads calling memory allocation/de-allocation.
>>>
>>> Webrev: http://cr.openjdk.java.net/~zgu/8009298/webrev.00/
>>>
>>> Tests:
>>> The test case is special version of runThese, it uses 12 threads to 
>>> load/unloading classes without executing any tests.
>>>
>>> Following two memory usage graphs show the different behavior with 
>>> AutoShutdownNMT on/off.
>>>
>>> AutoShutdownNMT = true
>>> http://cr.openjdk.java.net/~zgu/8009298/webrev.00/autoShutdown.png
>>>   The steep drop in memory usage was result of shutting down of 
>>> native memory tracking.
>>>
>>> AutoShutdownNMT = false
>>> http://cr.openjdk.java.net/~zgu/8009298/webrev.00/noAutoShutdown.png
>>>    The steep dig was result of class unloading.
>>>
>>>
>>> Thanks,
>>>
>>> -Zhengyu
>>>
>>
>