Introduction

The purpose of this article is to provide prescriptive guidance on how to troubleshoot free system page table entries (PTEs) in regards to Windows performance analysis.

Start with the following performance counters to analyze free system PTE’s:

· \Memory\Free System Page Table Entries

A page table is the data structure used by the Windows Virtual Memory Manager (VMM) to store the mapping between virtual addresses and physical addresses in memory. The performance counter Free System Page Table Entries is the number of page table entries not currently used by the system.

From the process perspective, each element of virtual address conceptually refers to a byte of physical memory. It is the responsibility of the Virtual Memory Manager (VMM) in conjunction with processor memory management unit (MMU) to translate or map each virtual address into a corresponding physical address.

The VMM performs the mapping by dividing the RAM into fixed-size page frames, creating system PTEs to store information about these page frames, and mapping them. System PTEs are small kernel-mode buffers of memory that are used to communicate with the disk I/O subsystem and the network. Each PTE represents a page frame and contains information necessary for the VMM to locate a page.

Note: Troubleshooting System PTE’s is explained in more detail at in the “Detection, Analysis, and Corrective Actions for Low Page Table Entry Issues” article mentioned in the References section below.

Applies to:

• Microsoft Windows 2000 Service Pack 1
• Microsoft Windows 2000 Service Pack 2
• Microsoft Windows 2000 Advanced Server

Symptom Details:

• Lack of Free System Page Table Entries (PTEs): Use the “Memory\Free System Page Table Entries” performance counter for values under 5000. Alternatively, the !pte command in the kernel debugger can be used to examine PTEs.
• Error Message: ERROR_NO_SYSTEM_RESOURCES (1450): The error message: ERROR_NO_SYSTEM_RESOURCES (1450) appears in a bug check (blue screen) in Windows.

Possible Cause: SCSI miniport driver instructs the Scsiport.sys file to map buffers, the Scsiport.sys file tries to map the buffer that is described by the I/O request packet's MDL

How to Diagnose

· Run “Winver” or Add/Remove Programs to determine the latest service pack applied to windows.

Possible Solutions and/or Recommendations

· Obtain the latest Service Pack for Windows 2000: Apply the latest service pack for Windows 2000. See the following article for more information: http://support.microsoft.com/?id=291228

References:

• Detection, Analysis, and Corrective Actions for Low Page Table Entry Issues
  http://www.microsoft.com/downloads/details.aspx?FamilyID=ed0e8084-abf7-4c00-ba6a-7d658cdb052a&DisplayLang=en
• “Windows Internals Microsoft Windows Server 2003, Windows XP, and Windows 2000” by Mark E. Russinovich and David Soloman.
• Comparison of 32-bit and 64-bit memory architecture for 64-bit editions of Windows XP and Windows Server 2003
  http://support.microsoft.com/kb/294418
• System Pages
  http://technet2.microsoft.com/windowsserver/en/library/c5ccbaec-f552-4f61-a488-8ee3330d1eeb1033.mspx?mfr=true
• How to use the /userva switch with the /3GB switch to tune the User-mode space to a value between 2 GB and 3 GB
  http://support.microsoft.com/kb/316739

Contributors:

Clint Huffman, Shane Creamer, Rick Anderson, Maximilian Silva, Matthew Walker, Pavel Lebedynskiy, John Rodriguez, Mike Lagase, Yong Rhee