Symptoms: Lack of Free System Page Table Entries (PTEs) and no system-wide delays

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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:

  • 32-bit Windows Server 2003 (all editions) unless otherwise specified

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.
  • No periodic system-wide delays: No system-wide delays or hangs that occur regularly or occur during elevated load on the system. This is measured by the user experience and I/O response times of the system.

 

Possible Cause: Inaccurate data

How to Diagnose

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

Possible Solutions and/or Recommendations

· Install Windows Server 2003 Service Pack 1: The Performance Monitor “Memory\Free System Page Table Entries” counter is inaccurate on installations of Windows Server 2003 without Service Pack 1. For more information about this topic, see Microsoft Knowledge Base article 894067 “The Performance tool does not accurately show the available Free System Page Table entries in Windows Server 2003” (https://go.microsoft.com/fwlink/?linkid=3052&kbid=894067)

References
Contributors:

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