5.5.4 Performance Flame Graph

Feature Introduction

A flame graph is a visual representation of performance data collected by tools such as perf. It statistically analyzes the data to help easily identify performance hotspots.

Each box in the flame graph represents a function. The width of the box indicates its execution time—thus, wider functions take longer to execute.

Each higher level ("floor") in the flame graph represents a deeper level of function calls. The topmost functions are leaf functions (functions that do not call other functions).

Code repository: (https://github.com/brendangregg/FlameGraph.git)

Supported Platforms

Platform	Execution Environment
RDK X3, RDK X3 Module, RDK X5, RDK X5 Module	Ubuntu 20.04 (Foxy), Ubuntu 22.04 (Humble)
RDK Ultra	Ubuntu 20.04 (Foxy)

Prerequisites

RDK Platform

1. The flamegraph tool consists of two parts. The first part is the executable program perf. perf is a software performance analysis tool used to collect and output statistics about function calls within the system or a specific process. The perf tool is already included in the RDK operating system, so it can be used directly.

2. The second part of the flamegraph tool is a script that parses perf's textual output. This script processes the text data generated by perf and produces an SVG-formatted flame graph of function calls, making it easier to observe and analyze.

Usage Instructions

1. Use the perf record tool to sample function calls within the RDK system and generate a perf.data file:

   root@ubuntu:~# perf record -F 99 -a -g -- sleep 60

2. Use perf script to parse the perf.data file and generate out.perf:

   root@ubuntu:~# perf script > out.perf

3. On your PC or RDK device, run git clone https://github.com/brendangregg/FlameGraph.git, enter the flamegraph directory, and copy the out.perf file generated in step 2 into this directory. Then use stackcollapse-perf.pl from the flamegraph toolkit to "fold" the out.perf data into out.folded:

   ./stackcollapse-perf.pl out.perf > out.folded

4. Use flamegraph.pl to generate the SVG flame graph:

   ./flamegraph.pl out.folded > flame.svg

Steps 1 and 2 are performed on the RDK device, while steps 3 and 4 can be carried out either on a PC or on the RDK device.

Result Analysis

Following the procedure described above, the recorded function calls within the RDK system appear as shown in the figure below: