Sys (VSPerfCmd)
Applies to: 
Visual Studio 
Visual Studio for Mac
Note
This article applies to Visual Studio 2017. If you're looking for the latest Visual Studio documentation, see Visual Studio documentation. We recommend upgrading to the latest version of Visual Studio. Download it here
The VSPerfCmd.exe Sys option sets the profiling event that is sampled to system call events (function calls from the profiled application to the operating system), and optionally changes the number of system calls in a sampling interval from the default of 10.
Sys can only be used in a command line that also contains the Launch or the Attach option.
By default, the profiler sampling event is set to processor clock cycles and the sampling interval is set to 10,000,000. The Timer, PF, Sys, and Counter options enable you to set the sampling event and the sampling interval. The GC option collects .NET memory data at each allocation and garbage collection event. Only one of these options can be specified on a command line.
The sampling event and the sampling interval can be set only in the first command line that contains a Launch or an Attach option.
Syntax
VSPerfCmd.exe {/Launch:AppName|Attach:PID} /Sys[:Events] [Options]
Parameters
Events
An integer value that specifies the number of system call events in a sampling interval. If Events is not specified, the interval is set to 10.
Required Options
Sys requires one of the following options.
Launch: AppName
Starts the profiler and the application specified by AppName.
Attach: PID
Attaches the profiler to the process specified by PID.
Invalid Options
The following options cannot be specified on the same command line as Sys.
PF[:Events]
Sets the sampling event to page faults and optionally sets the sampling interval to Events. The default PF interval is 10.
Timer[:Cycles]
Sets the sampling event to processor clock cycles and optionally sets the sampling interval to Cycles. The default Timer interval is 10,000,000.
Counter: Name[,Reload[,FriendlyName]]
Sets the sampling event to the CPU performance counter specified by Name and sets the sampling interval to Reload.
GC[:{Allocation|Lifetime}] Collects .NET memory data. By default (Allocation), data is collected at every memory allocation event. When the Lifetime parameter is specified, data is also collected at each garbage collection event.
Example
This example demonstrates how to set the profiler sampling event to system calls and how to set the sampling interval to 20 calls per sample.
VSPerfCmd.exe /Start:Sample /Output:TestApp.exe.vsp
VSPerfCmd.exe /Launch:TestApp.exe /Sys:20