# Profiles Flamegraph

> Read a Last9 profiles flamegraph: frame width, self and total samples, zooming into call paths, function search, and hiding runtime frames.

Source: https://last9.io/docs/profiles/flamegraph/

Click a service name in the [services view](/docs/profiles/services/) to open its flamegraph in a side panel.

![Flamegraph for a service](../../../../assets/content/docs/profiles/profiles-flamegraph.png)

## Reading a Flamegraph

A flamegraph aggregates all sampled call stacks for the service in the selected range:

- **Each bar is a function** (a frame). The bar at the top, `root`, represents all samples.
- **Bars below a frame are the functions it called.** Read from top to bottom to follow the call path.
- **Width is the share of samples.** A wider bar means more CPU time was spent in that function and everything it called.
- **Colors group frames by package**, so you can spot a library or module across the graph. Color does not indicate severity.
- **Horizontal order is not time.** Frames are merged by call path, so left-to-right position has no meaning.

The flamegraph renders the top 1,000 stacks for the service, as shown by **Showing top 1,000 stacks** above the graph.

## Inspecting a Frame

Hover over a frame to see its **Self** and **Total** share. Click a frame to pin it in the **Frame details** panel:

| Field         | Meaning                                                                                              |
| ------------- | ---------------------------------------------------------------------------------------------------- |
| **Name**      | Fully qualified function name.                                                                       |
| **Self**      | Samples where this function was executing its own code (**Time in this frame**).                     |
| **Total**     | Samples where this function was on the stack, including functions it called (**Including callees**). |
| **StackHash** | Identifier of the hottest stack through this frame.                                                  |
| **File**      | Source file and line, when available for the runtime.                                                |

A frame with high **Total** but low **Self** is a caller: the cost is in the functions beneath it. A frame with high **Self** is where the CPU is actually burning.

## Zooming Into a Call Path

Click a frame to zoom in. The selected frame becomes the new top of the graph, and its callees expand to the full width so you can read narrow frames.

![Zoomed flamegraph showing a database read path](../../../../assets/content/docs/profiles/profiles-flamegraph-zoom.png)

The breadcrumb above the graph shows the zoom path, starting from **All**. Click any crumb to zoom back out to that level, or press `Esc` to zoom out.

In the CPU profile above, zooming into `database/sql.(*Rows).Next` shows a larger share of its samples in the socket-read path (`net.(*conn).Read` down to kernel `tcp_recvmsg`) than in row decoding. This is CPU spent in the database-read path, including kernel work receiving and copying socket data. The bar widths do not measure time blocked waiting for a database response. Corroborate with database spans in [Traces](/docs/traces/) or a wall-clock or off-CPU profile before concluding that database waiting is the bottleneck.

## Searching for Functions

Type in **Search functions** to highlight matching frames. Non-matching frames are dimmed, which makes it easy to see every place a function or package appears across call paths. Press `/` to focus the search box.

## Hiding Runtime Frames

Turn on **Hide runtime** to remove language runtime and system frames, such as Go `runtime.*`, garbage collection, `syscall.*`, `java.*`, libc, and `[unknown]` frames. Their children move up so that your application code takes up more of the graph.

![Flamegraph with runtime frames hidden](../../../../assets/content/docs/profiles/profiles-hide-runtime.png)

Use this to focus on code you own. Turn it off when you suspect the runtime itself, for example when garbage collection takes a large share of CPU.

:::tip
The same data is available as a sortable table in [Top Functions](/docs/profiles/top-functions/).
:::

---

## Troubleshooting

- **Flamegraph shows `[unknown]` frames**

  - **Frames appear as `[unknown]`.** The profiler could not resolve symbols for that process. This is common with stripped binaries and minimal images. Collection and ingestion are still working. See [Kubernetes Profiling](/docs/integrations/observability/kubernetes-profiling/) for details.
  - **Old frames stay unknown after a fix.** Frames are not re-symbolized after ingestion. Only new samples show resolved names.

Please get in touch with us on [Discord](https://discord.com/invite/Q3p2EEucx9) or [Email](mailto:cs@last9.io) if you have any questions.