Messages in this thread | | | From | Song Liu <> | Subject | Re: [RFC] perf/core: allow ftrace for functions in kernel/event/core.c | Date | Wed, 27 May 2020 18:40:33 +0000 |
| |
> On May 26, 2020, at 10:40 PM, Masami Hiramatsu <mhiramat@kernel.org> wrote: > > On Tue, 26 May 2020 21:46:29 +0000 > Song Liu <songliubraving@fb.com> wrote: > >> >> >>> On May 26, 2020, at 2:39 PM, Peter Zijlstra <peterz@infradead.org> wrote: >>> >>> On Tue, May 26, 2020 at 02:28:26PM -0700, Song Liu wrote: >>>> It is useful to trace functions in kernel/event/core.c. Allow ftrace for >>>> them by removing $(CC_FLAGS_FTRACE) from Makefile. >>> >>> Did you try using the ftrace event with perf with this on? >> >> I have tried a few things, like >> >> perf stat -e probe:perf_read -I 1000 >> perf record -e probe:__x64_sys_perf_event_open -aR >> >> They all work fine. > > Did you try using perf with function-tracer or function-graph tracer? > If you just want to trace those functions with kprobes, you can > build your kernel with CONFIG_KPROBE_EVENTS_ON_NOTRACE=y, which allows > you to probe perf_read etc.
Thanks for the hint.
kprobe does work with CONFIG_KPROBE_EVENTS_ON_NOTRACE, but BPF trampoline doesn't work. If it is safe, removing $(CC_FLAGS_FTRACE) is preferable.
Thanks, Song
| |