Profiler: Analysis

DebugTools provides a number of cmdlets to analyze the data collected in a profiler trace. These cmdlets break down into the following categories:

• Methods
• Frames
• Exceptions

By default, all analysis cmdlets will operate against the implicit profiler session if no session is specified. Sessions can be retrieved using the Get-DbgProfiler cmdlet

Get-DbgProfiler -Id 1001 | Get-DbgProfilerMethod

For more information on the implicit profiler session, please see Session Management.

Unfortunately, as some cmdlet names are long to describe what they do, it can be a bit confusing trying to remember and type out the exact name of a cmdlet. It is recommended to use PowerShell auto-completion when typing out some of the longer cmdlet names in DebugTools. i.e. you can simply do

Show-Db <tab>

to auto-complete Show-DbgProfilerStackTrace

Methods

Once a target process has been launched containing the DebugTools Profiler, regardless of whether or not you are actively recording frame transitions, all methods JITted will be reported back to the profiler controller process. All frames currently known to the profiler controller can be listed using the Get-DbgProfilerMethod

C:\> Get-DbgProfilerMethod

FunctionID     ModuleName                       TypeName                                           MethodName
----------     ----------                       --------                                           ----------
0x7FFCBEFADF60 System.Management.Automation.dll <GetDefaultAvailableModuleFiles>d__2               <>m__Finally2
0x7FFCBEE10530 System.Management.Automation.dll System.Management.Automation.PowerShell            CoreInvoke
...

The Get-DbgProfilerMethod provides a number of parameters that can be used to search for target methods. The simplest way to search using Get-DbgProfilerMethod is to specify a wildcard expression specifying part of the fully qualified method name (including namespace, type and method name).

C:\> Get-DbgProfilerMethod *childitem*

Get-DbgProfilerMethod provides a number of parameters for performing more specific types of filtering: you can filter based on the -ModuleName, -TypeName, -MethodName and even -Exclude certain name patterns that you're not interested in.

By default, Get-DbgProfiler will search all methods that have been invoked since the target process was started. To search only for methods that were invoked in the last trace, specify the -LastTrace parameter.

C:\> Get-DbgProfilerMethod -TypeName *child* -LastTrace

Searching for methods from the last trace can sometimes be a better idea than trying to search for frames, or even drawing a visual stack trace. Once you've identified some potential methods you may be interested, you can jump to cmdlets like Show-DbgProfilerStackTrace which can sometimes take some time to run depending on the number of captured frames that need to be filtered.

To view the parameters available on Get-DbgProfilerMethod do Get-Help Get-DbgProfilerMethod

Frames

When a trace is stopped, the data collected in that trace is cached on the profiler session. The root frames of this trace can be retrieved using the Get-DbgProfilerLastStackTrace cmdlet

C:\> Get-DbgProfilerLastStackTrace

ThreadId ThreadName                Parent Children
-------- ----------                ------ --------
19516    Pipeline Execution Thread        {System.Management.Automation.Runspaces.Pipeline...
...

The data contained returned from this cmdlet can then potentially be cached and then passed to other cmdlets that analyze frames. If no frame is specified to a frame analysis cmdlet, an analysis will automatically be performed starting from the root frame of each thread in the last recorded trace. Due to the amount of memory a trace can potentially consume, if you wish to hold onto the output of a previous trace for potentially comparing two traces, you should keep an eye on your process/system memory, as this data will not be garbage collected as long as you are holding a reference to it.

Frames can be searched for using the Find-DbgProfilerStackFrame cmdlet. The Find-DbgProfilerStackFrame cmdlet supports specifying a wide array of parameters for narrowing down its search results.

# List all frames whose fully qualified name includes "childitem"
C:\> Find-DbgProfilerStackFrame *childitem*

Display                                               MethodInfo
-------                                               ----------
GetChildItemCommand.get_Force                         Microsoft.PowerShell.Commands.GetChildItemCommand.get_Force
GetChildItemCommand.get_Include                       Microsoft.PowerShell.Commands.GetChildItemCommand.get_Include
GetChildItemCommand.get_Exclude                       Microsoft.PowerShell.Commands.GetChildItemCommand.get_Exclude
...

To get a more visual feel for a stack trace, the Show-DbgProfilerStackTrace can be used. Show-DbgProfilerStackTrace supports all of the same parameters that Find-DbgProfilerStackFrame supports.

For a full list of parameters supported by all cmdlets, do Get-Help <cmdlet> within PowerShell

Get-Help Show-DbgProfilerStackTrace

Exceptions

A list of all exceptions captured in the last trace can be displayed via the Get-DbgProfilerException cmdlet

C:\> Get-DbgProfilerExceptionPS D:\> Get-DbgProfilerException

ThreadId Type                                                  Sequence Status ThrownFrame                        HandledFrame
-------- ----                                                  -------- ------ -----------                        ------------
3640     System.Management.Automation.CommandNotFoundException 1        Caught CommandDiscovery.LookupCommandInfo CommandDiscovery.TryNormalSearch
3640     System.IO.FileNotFoundException                       2        Caught ExecutionContext.LoadAssembly      ExecutionContext.LoadAssembly
...

Exceptions output can be limited to those that occurred on a specific -ThreadId or those that match a specific -Type

C:\> Get-DbgProfilerException *invalidoperation*