RFR(XXS) 8190357: NMT: Include metadata information in NMT final report when PrintNMTStatistics is on

[Zhengyu Gu]

Hi Andrew,

On 11/10/2017 04:22 AM, Andrew Dinn wrote:
> Hi Zhengyu,
> 
> On 09/11/17 19:33, Zhengyu Gu wrote:
>> This patch adds metadata reporting in NMT final report.
>>
>> What complicates the matter, is that, reporting per-class loader
>> metadata requires a safepoint, so that it can safely walk class loaders.
>> So, we only report it when JVM is about to exit in good state.
>>
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8190357
>> Webrev: http://cr.openjdk.java.net/~zgu/8190357/webrev.00/
> I understand the need here to avoid reporting if we are under a fatal
> error. However, that assert is not going to work in product code. So,
> does that not imply that execution of the vmop needs to be conditional
> on VMError::fatal_error_in_progress() returning false?

MemTracker::report() is a private method, only called by 
MemTracker::final_report() and MemTracker::error_report(). This 
assertion ensures that metadata report should never be included in 
MemTracker::error_report() if it decides to extend beyond summary report.

Of course, this is under assumption that final_report() is called during 
JVM normal shutdown (good state) and error_report() is by error handler 
(bad state).

Besides, VMError::fatal_error_in_progress() is inherently racy.

Thanks,

-Zhengyu


> 
> regards,
> 
> 
> Andrew Dinn
> -----------
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