Enable FTRACE in ARM to trace realtime characteristic of system

Question

I followed this article to enable FTRACE https://lwn.net/Articles/365835/

to test a realtime system, my system uses arm cortexa15 (Description: https://mp.renesas.com/en-us/rzg/marketplace/board/RZGB000003.html)

CONFIG_FTRACE=y
CONFIG_FUNCTION_TRACER=y
CONFIG_FUNCTION_GRAPH_TRACER=y
CONFIG_STACK_TRACER=y
CONFIG_DYNAMIC_FTRACE=y

But, it didn't work, caused the system hang-up when starting kernel. Even referred How to Enable or configure ftrace module

I would like to test latency in the realtime system with cyclictest (option -b to trigger FTRACER)

cyclictest -a -t -n -p99 -f -b100

It generated dump message:

INFO: debugfs mountpoint: /sys/kernel/debug/tracing/
WARN: tracing_enabled or tracing_on not found
debug fs not mounted, TRACERs not configured?
could not set ftrace_enabled to 0
FATAL: Can't open /sys/kernel/debug/tracing/available_tracers for reading

I repeated a next step to enable a group of tracer configs:

CONFIG_FTRACE=y
CONFIG_DYNAMIC_FTRACE=y
CONFIG_HAVE_DYNAMIC_FTRACE=y
CONFIG_HAVE_FUNCTION_TRACER=y
CONFIG_HAVE_FUNCTION_GRAPH_TRACER=y
CONFIG_HAVE_FTRACE_MCOUNT_RECORD=y
CONFIG_HAVE_SYSCALL_TRACEPOINTS=y
CONFIG_HAVE_C_RECORDMCOUNT=y
CONFIG_TRACING_SUPPORT=y
CONFIG_FUNCTION_TRACER=y
CONFIG_IRQSOFF_TRACER=y
CONFIG_FUNCTION_PROFILER=y
CONFIG_PREEMPT_TRACER=y
CONFIG_SCHED_TRACER=y
CONFIG_ENABLE_DEFAULT_TRACERS=y
CONFIG_FTRACE_SYSCALLS=y
CONFIG_TRACER_SNAPSHOT=y
CONFIG_STACK_TRACER=y
CONFIG_BLK_DEV_IO_TRACE=y
CONFIG_TRACEPOINT_BENCHMARK=y
CONFIG_BACKTRACE_SELF_TEST=y
CONFIG_EARLY_PRINTK=y
CONFIG_DEBUG_LL=y

The result still was the same. Kernel hung and didn't show anything.

Anyone who deal with realtime system and Ftrace can help ? Thanks.

score 0 · Answer 1 · answered Aug 30 '18 at 06:24

I resolve my problem. Below is a part of my defconfig file.

CONFIG_STACKTRACE_SUPPORT=y
CONFIG_TRACE_IRQFLAGS_SUPPORT=y
CONFIG_TRACEPOINTS=y
CONFIG_STACKTRACE=y
CONFIG_NOP_TRACER=y
CONFIG_TRACER_MAX_TRACE=y
CONFIG_TRACE_CLOCK=y
CONFIG_CONTEXT_SWITCH_TRACER=y
CONFIG_GENERIC_TRACER=y
CONFIG_FTRACE=y
CONFIG_FUNCTION_TRACER=y
CONFIG_FUNCTION_GRAPH_TRACER=y
CONFIG_SCHED_TRACER=y
CONFIG_FTRACE_SYSCALLS=y
CONFIG_TRACER_SNAPSHOT=y
CONFIG_STACK_TRACER=y
CONFIG_DYNAMIC_FTRACE=y
CONFIG_FTRACE_MCOUNT_RECORD=y

After enabling Ftrace tool, the culprit can then be found in the trace output at /sys/kernel/debug/tracing/trace. The kernel function that was executed just before a latency of more than 100 microseconds was detected is marked with an exclamation mark.

Enable FTRACE in ARM to trace realtime characteristic of system

1 Answers1