Performance · C++Draft
Profiling C++ performance in Qt applications
Measure before you optimize — the tools and workflow we use to find real bottlenecks in Qt desktop and embedded apps.
By Sandro Andrade · October 21, 2026 · 1 min read
"The UI feels slow" is a symptom, not a diagnosis. Good performance work starts with measurement.
Pick the right tool
- perf and Hotspot for CPU sampling on Linux
- Heaptrack for allocation hot spots
- QML Profiler in Qt Creator for bindings, JavaScript and scene graph
QSG_RENDER_TIMING=1to see frame timings on the target
A simple workflow
- Reproduce the slow scenario reliably.
- Record a baseline on the real target, not just a fast workstation.
- Fix the single biggest hotspot.
- Measure again and keep the numbers.
QElapsedTimer timer;
timer.start();
model->reload();
qDebug() << "reload took" << timer.elapsed() << "ms";
Common culprits in Qt apps
- Expensive QML bindings re-evaluated every frame
- Unnecessary model resets instead of fine-grained signals
- Image decoding on the GUI thread
Want a performance review of your application? Get in touch.