On Tue, May 26, 2020 at 09:46:29PM +0000, Song Liu wrote: > > > > On May 26, 2020, at 2:39 PM, Peter Zijlstra <pet...@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. > > Do you have some tricky functions that we should double check?
I've no idea what probe: does. iirc there's something like ftrace:function that is like regular function tracing. At some point using that made the kernel really sick due to recursion between ftrace and perf. Quite possibly that's been fixed, dunno.
