No reachable instances in Native memory screen

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guillaume.philippot
Posts: 2
Joined: Thu Jan 08, 2015 3:43 pm

No reachable instances in Native memory screen

Post by guillaume.philippot » Thu Jan 08, 2015 4:00 pm

Hello,

I am investigating a memory leak on a dump of 3.7GB and the figures I see in the native memory screen under the Committed memory tab seem very strange.

Code: Select all

Private - 3702244KB
	Managed heaps - 2299593KB
		Normal heap - 2098178KB
			Generation #0 - 132488KB
				Gaps - 127635KB
				Unreachable instances - 4854KB
			Generation #1 - 6527KB
				Gaps - 1KB
				Unreachable instances - 6526KB
			Generation #2 - 1959163KB
				Gaps - 1005116KB
				Unreachable instances - 954046KB
		Large heap - 187027KB
			Overhead/unused - 100185KB
			Unreachable instances - 86842KB
		Overhead - 14388KB
			Other - 14388KB
	Code - 5984KB
	JIT - 7104KB
	Runtime heap - 34236KB
	Other data - 1355327KB
Shared - 0KB
Potentially shared - 489724KB
As you see, none of the normal heaps contain Reachable instances. It makes no sense to me as the total figures in the overview screen (see attachment) are completely different.
MemProfiler.png
Could it be due to
  • a corrupted dump ?
  • a wrong interpretation of the figures ?
  • a bug in the software ?
Your help and insight is greatly welcome.

Regards,
Guillaume

Andreas Suurkuusk
Posts: 1000
Joined: Wed Mar 02, 2005 7:53 pm

Re: No reachable instances in Native memory screen

Post by Andreas Suurkuusk » Mon Jan 12, 2015 8:55 am

Thanks for the error report. This is a bug in the profiler that we have also noticed recently. Due to an optimization, the reachable instances are analysed in another stage of the heap snapshot collection. Now the reachable information is updated after the native memory information is reported, which causes all instances to be presented as unreachable in the native memory view.

We will fix this in the next release of .NET Memory Profiler. Hopefully, we will be able to present reachable and unreachable instances separately again, without incurring a too high performance cost. Otherwise we will just present instances, without specifying reachability in the native memory view. Information about unreachable instances can still be found in the Types view and Type details view.
Best regards,

Andreas Suurkuusk
SciTech Software AB

guillaume.philippot
Posts: 2
Joined: Thu Jan 08, 2015 3:43 pm

Re: No reachable instances in Native memory screen

Post by guillaume.philippot » Mon Jan 12, 2015 10:15 am

Thank you for your answser.
Andreas Suurkuusk wrote:This is a bug in the profiler [...] which causes all instances to be presented as unreachable in the native memory view.
And what about the gaps ? Are those figures correct ? Do we really have >1GB of gaps in our heaps or should we just not rely on the native memory view until the bug is fixed ?

Regards,
Guillaume

Andreas Suurkuusk
Posts: 1000
Joined: Wed Mar 02, 2005 7:53 pm

Re: No reachable instances in Native memory screen

Post by Andreas Suurkuusk » Mon Jan 12, 2015 3:22 pm

We're not aware of an error related to the presentation of gaps in the Native memory view. However, the numbers presented in your session does not look correct. We will look into this and see if we find any problems related to the identification of gaps.

It would be good if we could import your memory dump so that we can try reproduce the problem. Is there any possibility that you can send us the memory dump? If there is, please contact us at support@scitech.se.
Best regards,

Andreas Suurkuusk
SciTech Software AB

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