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From: Song Liu <songliubraving@fb.com>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Kernel Team <Kernel-team@fb.com>, Ingo Molnar <mingo@redhat.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	"Arnaldo Carvalho de Melo" <acme@redhat.com>,
	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: Wed, 27 May 2020 18:40:33 +0000	[thread overview]
Message-ID: <DD3FC894-134E-4A8E-A769-406FCC6B8F61@fb.com> (raw)
In-Reply-To: <20200527144040.3f12026f31b20b2011fbbcee@kernel.org>



> 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

      reply	other threads:[~2020-05-27 19:45 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
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 [this message]

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