From: Steven Rostedt <rostedt@goodmis.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Kernel Team <Kernel-team@fb.com>, Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Masami Hiramatsu <mhiramat@kernel.org>,
Mark Rutland <mark.rutland@arm.com>, Jiri Olsa <jolsa@redhat.com>,
Namhyung Kim <namhyung@kernel.org>,
Alexey Budankov <alexey.budankov@linux.intel.com>
Subject: Re: [RFC] perf/core: allow ftrace for functions in kernel/event/core.c
Date: Tue, 26 May 2020 18:04:37 -0400 [thread overview]
Message-ID: <20200526180437.45aed950@gandalf.local.home> (raw)
In-Reply-To: <20200526215415.GH2483@worktop.programming.kicks-ass.net>
On Tue, 26 May 2020 23:54:15 +0200
Peter Zijlstra <peterz@infradead.org> wrote:
> On Tue, May 26, 2020 at 09:46:29PM +0000, Song Liu 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.
> >
> > 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.
In the early days there was a lot of issues with recursions, but I added a
lot of recursion protection since then. I'll give this patch a spin and see
if I can make it crash.
-- Steve
next prev parent reply other threads:[~2020-05-26 22:04 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200526212826.4097888-1-songliubraving@fb.com>
2020-05-26 21:39 ` [RFC] perf/core: allow ftrace for functions in kernel/event/core.c Peter Zijlstra
2020-05-26 21:46 ` Song Liu
2020-05-26 21:54 ` Peter Zijlstra
2020-05-26 22:04 ` Steven Rostedt [this message]
2020-05-26 22:05 ` Steven Rostedt
2020-05-26 22:09 ` Song Liu
2020-06-05 21:58 ` Song Liu
2020-06-05 22:02 ` Steven Rostedt
2020-06-15 18:27 ` Song Liu
2021-09-24 17:15 ` Song Liu
2020-05-26 22:08 ` Song Liu
2020-05-27 5:40 ` Masami Hiramatsu
2020-05-27 18:40 ` Song Liu
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