linux-kernel - Re: [PATCH v2 00/15] tracing: 'hist' triggers

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Date:	Mon, 2 Mar 2015 12:48:52 -0800
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Karim Yaghmour <karim.yaghmour@...rsys.com>,
	Tom Zanussi <tom.zanussi@...ux.intel.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Andi Kleen <andi@...stfloor.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>
Subject: Re: [PATCH v2 00/15] tracing: 'hist' triggers

On Mon, Mar 2, 2015 at 12:43 PM, Steven Rostedt <rostedt@...dmis.org> wrote:
> On Mon, 2 Mar 2015 15:39:48 -0500
> Steven Rostedt <rostedt@...dmis.org> wrote:
>
>> On Mon, 2 Mar 2015 12:33:34 -0800
>> Alexei Starovoitov <ast@...mgrid.com> wrote:
>>
>> > On Mon, Mar 2, 2015 at 11:49 AM, Karim Yaghmour
>> > <karim.yaghmour@...rsys.com> wrote:
>> > >
>> > > On 15-03-02 02:45 PM, Steven Rostedt wrote:
>> > >> Interesting. The Android devices I have still have it enabled (rooted,
>> > >> but still running the stock system).
>> > >
>> > > I don't know that there's any policy to disable tracing on Android. The
>> > > Android framework in fact has generally been instrumented by Google
>> > > itself to output trace info into trace_marker. And the systrace/atrace
>> > > tools made available to app developers need to get access to this
>> > > tracing info. So, if Android had tracing disabled, systrace/atrace
>> > > wouldn't work.
>> > > https://developer.android.com/tools/debugging/systrace.html
>> >
>> > that's interesting. thanks for the link.
>> >
>> > I don't see tracing being explicitly enabled in defconfig:
>> > https://source.android.com/devices/tech/kernel.html
>>
>> CONFIG_SCHED_TRACER=y
>>
>> That alone will enable tracing.
>>
>> -- Steve
>>
>> > or here:
>> > https://android.googlesource.com/kernel/common/+/android-3.10/android/configs/android-recommended.cfg
>>
>
> CONFIG_ENABLE_DEFAULT_TRACERS=y
>
> And so will that.

good. thanks for explaining.
all makes sense now.

btw, that fancy systrace seems to be parsing text from trace_pipe
https://android.googlesource.com/platform/external/chromium-trace/+/jb-dev/src/tracing/linux_perf_importer.js
with a bunch of regex...
including sched_switch: next_prio...
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