tracing mini-HOWTO:

# mount -t debugfs nodev /sys/kernel/debug

# cat /sys/kernel/debug/tracing/available_tracers
wakeup preemptirqsoff preemptoff irqsoff function sched_switch nop

# cat /sys/kernel/debug/tracing/current_tracer
nop
# echo sched_switch > /sys/kernel/debug/tracing/current_tracer
# cat /sys/kernel/debug/tracing/current_tracer
sched_switch
# cat /sys/kernel/debug/tracing/trace_options
noprint-parent nosym-offset nosym-addr noverbose
# echo print-parent > /sys/kernel/debug/tracing/trace_options
# echo 1 > /sys/kernel/debug/tracing/tracing_enabled
# cat /sys/kernel/debug/tracing/trace > /tmp/trace.txt
# echo 0 > /sys/kernel/debug/tracing/tracing_enabled