Sampler

The sampler window is where you configure and start a sampling session. Open it from the Source Selection view in Qumulus. It walks through three steps.

Process Selection

The first step shows a list of all running processes with their name, PID and current CPU usage. Click a row to select it.

Processes that cannot be sampled are marked as inapt and shown in red. This is typically due to elevation levels or because no debug symbols could be found for that process. You can try to run Qumulus with increased privileges to gain access to these processes. The Show Inapt toggle makes these visible when you need to confirm why a process cannot be selected.

• macOS – debug symbols must be present as a .dSYM bundle alongside the executable.

• Windows – debug symbols must be present as a .pdb file alongside the executable.

Thread Selection

After selecting a process you can narrow profiling to specific threads. The list shows each thread’s name, ID (TID), current CPU usage and the function it is currently executing.

Leave all threads unchecked to profile every thread in the process. If you only care about a specific thread – for example the render thread – select only that one to keep the results focused.

Options

Fold Recursions

When enabled, consecutive identical stack frames caused by recursive calls are collapsed into a single entry. This prevents recursive functions from dominating the flame graph when you are interested in the higher-level call structure rather than recursion depth. Enabled by default.

Starting the Session

Press GO! to begin. Qumulus will connect to the sampler and data will start appearing in the timeline, just like with an instrumented application.