n. / Tracing basics
Trace waterfall
Definition
A trace waterfall is a chart that lays out the spans of one trace as horizontal bars on a shared time axis, indented by parent and child. It shows at a glance what ran in sequence, what ran in parallel and where the time went.
In more detail
Long bars are slow steps, gaps between bars are waiting or untraced work, and stacked bars that start together ran in parallel. Reading a waterfall is usually the first step when a run is slow, because it separates a slow model call from a slow tool, or from a chain of sequential calls that could run at the same time.
Example
Three tool calls run one after another, each taking 1.2 s. The waterfall shows them as a staircase. Running them in parallel would cut about 2.4 s from the run.
Related terms
