RFR(XS) 8191369: NMT: Enhance thread stack tracking

[Thomas Stüfe]

On Fri, Nov 17, 2017 at 2:46 AM, David Holmes <david.holmes at oracle.com>
wrote:

> Hi Andrew,
>
> On 17/11/2017 1:46 AM, Andrew Haley wrote:
>
>> On 16/11/17 06:58, David Holmes wrote:
>>
>> I can't review this in detail as I'm not familiar with NMT workings, but
>>> have a couple of comments.
>>>
>>> On 16/11/2017 8:25 AM, Zhengyu Gu wrote:
>>>
>>>> This is Linux only enhancement for now, can be extended for other
>>>> platforms. (See bug for details)
>>>>
>>>
>>> I'm concerned about unnecessary platform skew. I added some comments to
>>> the bug. I think the mincore trick can be used on Solaris and AIX as
>>> well - but not on OS X / BSD. It may be that VirtualQuery can be used on
>>> Windows to get the same information - but I'm unclear if the memory
>>> states support what you're looking for. It would be good to extend this
>>> to other platforms that will support it.
>>>
>>
>> Sure, but as OpenJDK becomes more open and hopefully more diverse, it
>> becomes less and less practical to keep everything in step.  I favour
>> the classic free software approach, which is to encourage people to
>> create new features and everyone else can fill in the gaps, depending
>> on how much time and effort is available.  It's this approach that
>> allows GCC to support a vast range of targets (and hosts) while not
>> holding back development.  I have consistently argued for this in the
>> Governing Board.
>>
>
> For OpenJDK I hope there are sufficient safety-nets in place to ensure
> such an approach does not lead to a product where you never know what will
> and won't work on each platform. Whenever we have such a case we should at
> least file sub-tasks for supplying the functionality on the missing
> platforms. We can then determine whether any such missing functionality is
> critical to fix before a release.
>
>
I agree. Also, I find that for platform-independent monitoring facilities
like NMT, I really just want to be able to trust the numbers without having
to peek at the implementation.

..Thomas


> David
> -----
>
>
> So, let's get this done.  It's very important for container memory
>> monitoring, which right now usually means Linux.
>>
>>