.NET memory allocation issue in version 4.5.2 under IIS RRS feed

  • Question

  • Hi,

    Apologies if this is in the wrong forum, but the general forum seems to have disappeared. Feel free to direct me to a more suitable place. Issue as follows:

    We have a customer running a Windows 2008 R2 64bit server running IIS 7.5 (more server info attached) with a 32bit IIS application running a mix of native and managed code.

    The memory usage under load rapidly over the space of minutes to an hour increases over 2 gig and eventually is terminated for hitting the virtual memory limit we have set at 3145728KB to gracefully recycling before crashing out with an out of memory exception.

    When not under load the same application and server does not increase memory usage but when under a load of as little as 100 sessions (no more than 5 concurrent requests) and a total number of requests less than 200 it has run out of memory in 3 or 4 minutes (increasing over 2gig). Simulating the same behaviour and requests over a longer period of time does not manifest a memory increase which remains stable.

    The working set and virtual bytes both increase over the time.

    We have been unable to replicate in our QA environment with similar servers and IIS.

    So far we have tried

    • Using a managed memory profiler (RedGate ABNTS profiler) which has not shown any leak/accumulation of managed objects
    • Taken a full memory dump from task manager, there appears to be a lot of free memory in the address space but new managed objects are being created at the end of the virtual address space.
    • Profiler has not shown an accumulation of the large object heap but did show some fragmentation, but still plenty of space our maximum sized object would be less than 5MB and very infrequent, under all the tracing we have not seen objects over 1MB. The total size of the large object heap also isn’t big enough.
    • Disabled internal application caching, confirmed by tracing / debug information that these caches are empty / not accumulating and limiting correctly.

    Within the application we do use

    • ASP.Net (WebForms)
    • ADO.Net
    • ODBC

    We are looking for any known issue with .Net memory allocation in version 4.5.2 and troubleshooting / investigation techniques in .Net/IIS to help us diagnose and resolve the memory increase to stabilize the application. Looking at historical logs the issue has been happening for a while but has doubled in frequency in the last product update in which we moved from .Net 4.5 to 4.5.2, we have so far not been able to identify any functional area that has changed that would explain this change in behaviour.

    Wednesday, March 8, 2017 3:15 PM


  • Hi Steve,

    This issue is hard to locate where it is. If your issue is URGENT,  I am afraid that forum is not suitable to support very urgent issue, I would suggest you to open one phone support ticket. Note: This is a paid service.

    Phone support channel: https://msdn.microsoft.com/en-us/library/bb266240.aspx

    Best regards,


    MSDN Community Support
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    • Marked as answer by Steve_Clark Thursday, March 9, 2017 9:37 AM
    Thursday, March 9, 2017 2:18 AM