Add documentation of ftrace backend. Signed-off-by: Eiichi Tsukata <eiichi.tsukata...@hitachi.com> --- docs/tracing.txt | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
diff --git a/docs/tracing.txt b/docs/tracing.txt index cf53c17..60ff9c5 100644 --- a/docs/tracing.txt +++ b/docs/tracing.txt @@ -175,6 +175,22 @@ unless you have specific needs for more advanced backends. The "simple" backend currently does not capture string arguments, it simply records the char* pointer value instead of the string that is pointed to. +=== Ftrace === + +The "ftrace" backend writes trace data to ftrace marker. This effectively +sends trace events to ftrace ring buffer, and you can compare qemu trace +data and kernel(especially kvm.ko when using KVM) trace data. + +if you use KVM, enable kvm events in ftrace: + + # echo 1 > /sys/kernel/debug/tracing/events/kvm/enable + +After running qemu by root user, you can get the trace: + + # cat /sys/kernel/debug/tracing/trace + +Restriction: "ftrace" backend is restricted to Linux only. + ==== Monitor commands ==== * trace-file on|off|flush|set <path> -- 1.8.1.4
