1. Windows Performance Troubleshooting and Analysis
Daniel Pearson
David Solomon Expert Seminars

2. Daniel Pearson Started working with Windows NT 3.51
Three years at Digital Equipment Corporation
Supporting Intel and Alpha systems running Windows NT
Seven years at Microsoft
Senior Escalation Lead in Windows base team
Worked in the Mobile Internet sustained engineering team
Instructor for David Solomon, co-author of the Windows Internals book series

3. Agenda Components of performance analysis
Understanding the tools for troubleshooting and analyzing performance issues
Troubleshooting CPU and memory issues using various Windows tools
Portions of this session are based on material developed by Mark Russinovich and David Solomon

4. Components of Performance Analysis
Event Tracing for Windows
Core component of the operating system
Kernel mode data structures
Used to store information about the system and system objects that can be read by various tools
e.g. dt nt!_KTHREAD KernelTime
CPU performance monitoring events
Refer to the Intel 64 and IA-32 Architectures Software Developer’s Manual

5. Event Tracing for Windows
Built in to the system
High performance, low overhead and scalable
2.5% CPU usage for a sustained rate of 10,000 events/sec on a 2 GHz CPU1
Operations throughout the system that are of interest to performance are fully instrumented
e.g. process and thread activity, registry I/O, disk I/O
Milirud, Michael Windows Performance Analysis: Using Windows Performance Tools. Presented at Microsoft's WinHEC conference, November 5-7, Los Angeles, CA.

6. Event Tracing for Windows
Uses a buffering and logging mechanism implemented in the kernel
Per-processor buffers that are written to disk by an asynchronous writer thread
Ability to enable and disable tracing dynamically
Supports a managed code provider

7. Sysinternals Utilities

8. Sysinternals Utilities
Process Explorer
Useful for displaying which files, registry keys and other objects processes have open and which DLLs they have loaded
Process Monitor
Useful for showing real-time file system, registry and process & thread activity
Available for download from the TechNet site

9. Resource Monitor

10. Resource Monitor
Included with Windows Vista and greatly enhanced in Windows 7 and Windows Server 2008 R2
Allows the viewing of CPU, memory, disk and network resources as well as handles and modules in real time
Ability to end, suspend and resume processes as well as to start, stop and restart Windows services
Useful for identifying the highest resource consumers by individual resource type, e.g. CPU
Able to list the wait chain tree of a process to determine if a process is waiting on another

11. Using Resource Monitor

12. Performance Monitor

13. Performance Monitor
Queries performance counters that measure system state or activity
Current values are read at specific intervals
Performance counters are included in the operating system and can be included as part of applications
Able to collect event trace data from trace providers that report actions or events
Can combine multiple trace providers into a single session
Configuration information can be collected from registry keys at a specific time or interval

14. Using Performance Monitor

15. Windows Performance Analyzer

16. Windows Performance Analyzer
Part of the Windows Performance Toolkit
Support for both x86, x64, and IA64 architectures
Consists of three primary programs
xperf.exe
Used for controlling tracing and processing trace data
xbootmgr.exe
Automates on and off state transitions and captures traces during those transitions
xperfview.exe
A graphical trace visualization tool to represent data in the form of interactive graphs and summary tables

17. Windows Performance Analyzer
Primarily uses the Event Tracing for Windows infrastructure built in to the system
Can be enabled or disabled at any time without requiring a system or process restart
Supports symbol decoding, sample profiling, and recording of call stacks on kernel events
Designed to be used during automation
All the functions of the tools are available via the command line tool xperf.exe

18. Support for Earlier Systems
The Windows Performance Toolkit will fail to install on Windows XP and on Windows Server 2003 although data collection is supported
Copy xperf.exe and perfctrl.dll
Trace analysis is only supported on Windows Vista and later systems

19. Capturing a Performance Trace
Kernel options divided into two parts
Kernel Flags
Identified by the use of uppercase characters
e.g. PROC_THREAD, LOADER, PROFILE
Kernel Groups
Indentified by the use of title case characters
e.g. Base, Diag, Latency, FileIO
Kernel Groups are made up of a collection of Kernel Flags
e.g. SysProf = PROC_THREAD+LOADER+PROFILE
Flags and groups are separated by the ‘+’ token
e.g. xperf.exe -on FileIO+DISK_IO_INIT

20. Merging of Performance Trace Data
Traces can be copied to another system for analysis
The trace file should be “merged” on the collection system before analysis to include additional system information
xperf -d trace.etl
System and symbol information
Trace
Merged trace
Kernel trace
XPerf

21. Using the Windows Performance Toolkit

22. Understanding CPU Activity
Windows uses 32 priority levels
The system implements a preemptive, priority driven scheduler
Priority adjustments can be applied to threads in the “dynamic” range
At least one runnable thread with the highest priority will be running 31
Real time 16 15
Dynamic

23. Context Switching
A switch from one thread to another is known as a context switch
Switching involves saving the hardware state of a thread and restoring the state of another
When a thread is scheduled, that thread’s context switch count is also incremented
The context switch count represents how often a thread begins running, not how long it ran

24. Time Accounting Quirks
Looking at total CPU time for each process may not reveal where the system has spent its time
CPU time accounting is driven by an interrupt timer which is set by the Hardware Abstraction Layer
Usually at either 10 or 15 msec intervals
Thread execution and context switches that happen between clock intervals are not accounted for
e.g. a thread runs and enters a wait before the clock fires
Thus threads may run but never get charged

25. Time Accounting Prior to Windows Vista
Windows accounted for CPU time based on the interval clock timer
Thread quantum expiration was not always fair
A thread might get almost no turn
Threads were also charged for interrupts that occurred while they were running
Idle
Idle T1 T2 T2

26. Time Accounting Since Windows Vista
Windows Vista and later reads the Time Stamp Counter during every context switch
The actual CPU cycles consumed are charged to a thread
Any interrupt time is not charged to the interrupted thread
Allows for more accurate quantum accounting
A thread gets at least one turn and at most will be given one turn plus an additional tick
Idle
Idle T1 T1 T2

27. Troubleshooting High CPU Utilization

28. Understanding Memory Management
Windows provides two system memory pools
Nonpaged Pool and Paged Pool
Used for system wide persistent data
Prior to Windows Vista, pool sizes were a function of memory size and whether or not the system was configured as a server or a workstation
Windows Vista introduced the concept of a dynamic system address space

29. Dynamic System Address Space
In 32-bit Windows Vista and later, virtual memory is assigned as needed
Permits larger paged, nonpaged, and session pools
Components still cannot exceed 2 GB on 32-bit systems
On 64-bit systems, address space regions are configured to their current maximum limits for all memory sizes

30. Troubleshooting Memory Leaks

31. Additional Information
Windows Internals 5th edition
Windows Performance Analysis Developer Center
Windows Server Performance Team Blog
Ask the Performance Team Blog

32. Additional Information
David Solomon Expert Seminars offers training on Windows Internals both as public and private workshops and public webinars via the Internet
Currently scheduled up and coming classes
Public workshop in London, April 12th – April 16th
Public webinar, April 26th & April 28th
Public workshop in New York, May 3rd – May 7th
Public workshop in San Francisco, November 8th – November 12th
Visit for further course descriptions and up to date information