Chapter 18. Getting started with flamegraphs

Procedure

• Install the flamegraphs package:

  # dnf install js-d3-flame-graph

Prerequisites

• flamegraphs are installed as described in Installing flamegraphs.
• The perf tool is installed as described in Installing perf.

Procedure

• Record the data and create the visualization.

  # perf script flamegraph -a -F 99 sleep 60

  This command samples and records performance data over the entire system for 60 seconds, as stipulated by use of the sleep command, and then constructs the visualization which is stored in the current active directory as flamegraph.html. The command samples call-graph data by default and takes the same arguments as the perf tool, in this particular case:

  -a

  Stipulates to record data over the entire system.

  -F

  To set the sampling frequency per second.

Verification

• For analysis, view the generated visualization:

  # xdg-open flamegraph.html

  This command opens the visualization in the default browser:

Prerequisites

• flamegraphs are installed as described in Installing flamegraphs.
• The perf tool is installed as described in Installing perf.

Procedure

• Record the data and create the visualization.

  # perf script flamegraph -a -F 99 -p ID1,ID2 sleep 60

  This command samples and records performance data of the processes with the process ID’s ID1 and ID2 for 60 seconds, as stipulated by use of the sleep command, and then constructs the visualization which will be stored in the current active directory as flamegraph.html. The command samples call-graph data by default and takes the same arguments as the perf tool, in this particular case:

  -a

  Stipulates to record data over the entire system.

  -F

  To set the sampling frequency per second.

  -p

  To stipulate specific process ID’s to sample and record data over.

Verification

• For analysis, view the generated visualization:

  # xdg-open flamegraph.html

  This command opens the visualization in the default browser:

Procedure

• To reveal the names of functions which may have not been displayed previously and further investigate the data, click the box within the flamegraph to zoom into the stack at that given location:

  

• To return to the default view of the flamegraph, click Reset Zoom.

  Important

  Boxes representing user-space functions may be labeled as Unknown in flamegraphs because the binary of the function is stripped. Install the debuginfo package or compile your local application with debugging information enabled. Use the -g option in GCC, to display the function names or symbols in such a situation.