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How to prevent high paging on certain Windows versions?

This blog discusses a specific paging performance issue on Windows Server 2012, 2012 R2, 2016 and 2019.

If you operate a SAP ABAP Dialog Instance on Windows you maybe experience a very high paging rate (write operations).

Here is an example from Windows Resource Monitor:

Do you notice the orange bar? It displays the modified memory pages, which will be soon written to the pagefile, due to memory optimization of the Windows kernel.

 

You can see this type of paging in Disk tab of Resource Monitor:

The Windows kernel itself (System PID 4) writes with 208 Mbyte/sec to the Pagefile, in this example on c:\pagefile.sys. You may notice, that the priority for this is “Background I/O”.
Even it is background I/O it will cause bad performance issues!

The solution for this behavior was delivered by Microsoft with the July 2019 patches for

Windows Server 2012 R2

Windows Server 2016

Windows Server 2019

Remark:

Microsoft does not fix this behavior in Windows Server 2012!
Windows 2008 R2 is not affected!

To get rid of the above described paging problem, you must do two things:

  1. Install the patches of July 2019 (or later) via Windows Update
  2. Set a registry key value to enable the patch (requires reboot of the OS)

Add this value via Registry Editor (regedit) or using PowerShell commands:

Path HKLM\System\CurrentControlSet\Services\disk
Value IdleClassSupported
Type REG_DWORD
Data 1

If the patch is working, you do not see any high page writes to the Pagefile in Windows Resource Monitor anymore.

What you see, is a background I/O to Pagefile.sys of ~ 1 Mbyte/sec with a very strange high response time (more than a second!). This indicates, that the patch Microsoft created to prevent the high page writes to pagefile.sys, is working properly.

Example:

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  • Suppi, Danke für die Info, das werden wir sofort probieren.

    Thank you very much for sharing this information. We will try this asap.

    Ohh Servicing Stack Update is in July Patches included!? (was will uns das sagen)

  • Karl-Heinz Hochmuth

    “What you see, is a background I/O to Pagefile.sys of ~ 1 Mbyte/sec with a very strange high response time (more than a second!). This indicates, that the patch Microsoft created to prevent the high page writes to pagefile.sys, is working properly.”

    You’re very right 🙂

    But one side effect: saposcol now recognizes 100% disk utilization nearly all the time. Windows resource monitor shows the same, maybe because of the response times at accessing the page file.
    But as far as i understand, this utilization should be no problem – right?

    At SAP-point of view, it’s missleading in Wily or ST06 f.e. Is there any chance to fix this?

  • Hello Florian,

    you are right: The fix has the bad side affect, that the disk utilization on the disk, which hosts the pagefile, is wrong.

    This utilization is a “fake”, because the I/O does not occur in reality. Anyway, I understand that this must be fixed in saposcol. We start working on this issue.

    You can support us if you open a ticket (ask the colleagues to put it directly on my name (Karl-Heinz Hochmuth)) and then we will provide a fix for saposcol.

    My recommendation at this point in time:

    1. Do not put pagefile.sys on c: drive, put it on an extra drive, for example p:
    2. Turn off the monitoring for p: (or simply ignore p:)

    Thanks for your feedback!

     

    Best regards,

     

    Kalle