RFR: 8138705: Kitchen sink stress test fails

[Zhengyu Gu]

Hi Max,


On 05/17/2016 03:53 PM, Max Ockner wrote:
> Hello,
> I have responded to suggestions from Coleen and Zhengyu.
>
> New webrev: http://cr.openjdk.java.net/~mockner/8138705.02/
>  - Removed print statements
>  - Added check to break out of loop once we reach the end of the 
> region being committed
>
> Thanks,
> Max
>
> On 5/17/2016 9:06 AM, Zhengyu Gu wrote:
>> Hi Max,
>>
>> I have not done a complete review.
>>
>> virtualMemoryTracker.cpp:  63 - 88
>>
>> Is it possible that newly committed region does not overlap, but 
>> covers an existing region?
>>
You did not answer above question. If incoming committed region covers 
existing region(s), but does not overlap or adjacent to any the existing 
region(s), it will be added as new region.

As use cases get complicated, I think that it is simpler to always 
delete the region(s), then add.


src/share/vm/utilities/linkedlist.hpp

Nice catch.

-Zhengyu

>> The loop can stop when rgn->end_addr >= addr + size
>>
>> -Zhengyu
>>
>>
>> On 05/13/2016 03:39 PM, Max Ockner wrote:
>>> Hello,
>>> Please review this fix which allows NMT to handle overlapping commits.
>>>
>>> Though it would make sense to uncommit space before committing over 
>>> it,  this is not always the way things are done. Kitchensink 
>>> encounters some intentional overlapping commits in gc, which 
>>> previously would cause NMT to throw an assert. Now, these 
>>> overlapping commits are handled by recording an uncommit of the 
>>> newly committed region before recording the commit. This effectively 
>>> chops any of the already-committed space off of the existing 
>>> committed region before adding the new commit.  In order for this 
>>> all to work, ReservedMemoryRegion::remove_uncommitted_region was 
>>> changed to support uncommitting an arbitrary region. The target 
>>> behavior of this operation is to truncate (or split) committed 
>>> regions which overlap with the region being uncommitted, while only 
>>> subtracting from the total  the amount of memory which was actually 
>>> cleared.
>>>
>>> Bug:  https://bugs.openjdk.java.net/browse/JDK-8138705
>>> Webrev:  http://cr.openjdk.java.net/~mockner/8138705/
>>>
>>> Tested with jtreg NMT tests. Survived 72 hours of Kitchensink.
>>> Added a test: runtime/NMT/CommitOverlappingRegions.java
>>> This test performs various commits and uncommits that overlap in 
>>> different ways, and checks that it computes the amount of committed 
>>> space correctly.
>>>
>>> Thanks,
>>> Max
>>
>