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SubjectRe: [RFC] perf/core: allow ftrace for functions in kernel/event/core.c
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.

Thank you,


--
Masami Hiramatsu <mhiramat@kernel.org>

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