Debugging Linux Kernel using ftrace Part15 - trace_options

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'trace_options' file allows user to control the level of information displayed when we do cat on 'trace' or 'trace_file'


You can see from the above screenshot, There are 26 options available for the user to control. There are some tracer specific options which are not listed in this file and are present in 'options' directory.

The words which begin with "no" represents trace options that are disabled.

To enable an option.

$ echo 'sym-offset' > trace_options

To disable an option, add "no"

$ echo 'nosym-offset' > trace_options.

Let's try some of the options.

1. sym-offset: Enabling this option, you will see function name plus offset in the function. By default, this is disabled.


2. print-parent: This option displays the calling function. By default, this option is disabled.




3. function-fork: This option enables tracing the children when set_ftrace_pid is set.
4. irq-info: Displays the interrupt, preempt count, need resched data information in the trace


5. context-info: Disabling this option, will hide the Task-PID, CPU, Timestamp and other useful information.


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