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

[Masami Hiramatsu]

On Tue, 26 May 2020 21:46:29 +0000
Song Liu <songliubraving@xxxxxx> wrote:

> 
> 
> > On May 26, 2020, at 2:39 PM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> 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@xxxxxxxxxx>