Ftrace

Description

Ftrace is an internal tracer designed to help out developers and designers of systems to find what is going on inside the kernel. It can be used for debugging or analyzing latencies and performance issues that take place outside of user-space.

enable related config

1. From "make menuconfig", go to --> "Global Build Settings" then go to --> "Compile kernel with tracing support"

2. In the "Compile kernel with tracing support", enable the below options :-

   • Enable/disable function tracing dynamically

   • Trace process context switches and events

   • Function tracer

3. Once above changes are done, then from the "make kernel_menuconfig", go to --> "Kernel hacking" --> then enable the below options in "Tracers":-

   • Kernel Function Tracer

   • enable/disable function tracing dynamically

check enable status

ls /sys/kernel/debug/tracing/

enable ftrace on runtime

#********************************************#
# enable ftrace
#********************************************#
# To enable function tracing during run time
echo 0 > /sys/kernel/debug/tracing/tracing_on
echo function > /sys/kernel/debug/tracing/current_tracer
echo 1 > /sys/kernel/debug/tracing/tracing_on

# To enable specific events to be traced
echo tlet_entry >> /sys/kernel/debug/tracing/set_event
echo tlet_exit >> /sys/kernel/debug/tracing/set_event
echo irq_handler_entry >> /sys/kernel/debug/tracing/set_event
echo irq_handler_exit >> /sys/kernel/debug/tracing/set_event
echo softirq_entry >> /sys/kernel/debug/tracing/set_event
echo softirq_exit >> /sys/kernel/debug/tracing/set_event
echo timer_expire_entry >> /sys/kernel/debug/tracing/set_event
echo timer_expire_exit >> /sys/kernel/debug/tracing/set_event
echo sched_switch >> /sys/kernel/debug/tracing/set_event

# To Dump the FTrace to the console in case of oops
echo 1 > /proc/sys/kernel/ftrace_dump_on_oops

# To increase the size of Ftrace buffer per CPU
echo 2048 > /sys/kernel/debug/tracing/buffer_size_kb

# To enable tracing of signals
echo SyS_reboot:dump > /sys/kernel/debug/tracing/set_ftrace_filter
echo 1 > /sys/kernel/debug/tracing/events/signal/enable
echo 1 > /sys/kernel/debug/tracing/tracing_on
sysctl -w kernel.ftrace_dump_on_oops=1