This project demonstrates the process of profiling heap allocations in a Rust application on Windows using the Windows Performance Toolkit. It performs heap allocations of different sizes and uses wpr to capture these allocations.

Heap profiling requires running wpr with administrative privileges. Because the application runs wpr directly, it must be run with administrative privileges too.

• The latest available version of Windows Performance Toolkit.

git clone --depth 1 https://github.com/Vaiz/rust-wpr.git
cd rust-wpr
# For demonstrative purposes, it's better to build a debug version of the application
cargo run heapsnapshot.etl
wpa heapsnapshot.etl 

1. Open the .etl file in Windows Performance Analyzer (WPA).
2. Add the path to debug symbols:
   • Go to Trace -> Configure Symbols Path -> Add Entry.
   • 
3. Load symbols:
   • Go to Trace -> Load Symbols.
4. Dive into captured stacks:
   • Navigate to Graph Explorer -> Memory -> Heap Snapshot.
   • 

In the Analysis window, you will see all snapshots created by wpr. You can expand each snapshot to see all recorded allocations that were not freed at the moment of snapshot creation. It shows the stack where the allocation happened, the number of allocations, and the size.

A good official example can be found here.

To make sure that all the important allocations are captured, wpr has to be started before they happen.

1. Start Process Explorer or Task Manager to monitor RAM consumption and find the process PID.
2. Start PowerShell with admin privileges to run WPR.
3. Start your application.
4. Run wpr to enable and start snapshot creation.
5. Take snapshots at important points. It is also possible to enable automatic snapshot creation with wpr -enableperiodicsnapshot heap <frequency in seconds> <pid for foo.exe>.
6. Save collected data to a file.
7. Disable the profiler.

You can use the script below as a base:

$ppid = 12345
wpr -snapshotconfig heap -pid $ppid enable
wpr -start heapsnapshot -filemode

# Ensure this command is executed right after the application starts, before any significant memory allocations occur
wpr -singlesnapshot heap $ppid
#  Execute this command again whenever the application reaches a critical or interesting state
wpr -singlesnapshot heap $ppid

wpr -stop heapsnapshot.etl
wpr -snapshotconfig heap -pid $ppid disable