Re: [RFD] Future tracing/instrumentation directions [LWN.net]

From:		Ingo Molnar <mingo-AT-elte.hu>
To:		Thomas Gleixner <tglx-AT-linutronix.de>
Subject:		Re: [RFD] Future tracing/instrumentation directions
Date:		Thu, 20 May 2010 13:42:18 +0200
Cc:		Frederic Weisbecker <fweisbec-AT-gmail.com>, Steven Rostedt <rostedt-AT-goodmis.org>, LKML <linux-kernel-AT-vger.kernel.org>, Linus Torvalds <torvalds-AT-linux-foundation.org>, Andrew Morton <akpm-AT-linux-foundation.org>, Peter Zijlstra <peterz-AT-infradead.org>, Christoph Hellwig <hch-AT-lst.de>, Mathieu Desnoyers <mathieu.desnoyers-AT-efficios.com>, Li Zefan <lizf-AT-cn.fujitsu.com>, Lai Jiangshan <laijs-AT-cn.fujitsu.com>, Johannes Berg <johannes.berg-AT-intel.com>, Masami Hiramatsu <masami.hiramatsu.pt-AT-hitachi.com>, Arnaldo Carvalho de Melo <acme-AT-infradead.org>, Tom Zanussi <tzanussi-AT-gmail.com>, KOSAKI Motohiro <kosaki.motohiro-AT-jp.fujitsu.com>, Andi Kleen <andi-AT-firstfloor.org>, Masami Hiramatsu <mhiramat-AT-redhat.com>, Lin Ming <ming.m.lin-AT-intel.com>, Cyrill Gorcunov <gorcunov-AT-gmail.com>, Mike Galbraith <efault-AT-gmx.de>, Paul Mackerras <paulus-AT-samba.org>, Hitoshi Mitake <mitake-AT-dcl.info.waseda
Archive-link:		Article, Thread


* Thomas Gleixner <tglx@linutronix.de> wrote:

> On Thu, 20 May 2010, Frederic Weisbecker wrote:
> > On Thu, May 20, 2010 at 11:31:31AM +0200, Ingo Molnar wrote:
> > >  - [ While it's still a long way off, if this trend continues
> > >      we eventually might even be able to get rid of the 
> > >      /debug/tracing/ temporary debug API and get rid of 
> > >      the ugly in-kernel pretty-printing bits. This is 
> > >      good: it may make Andrew very happy for a change ;-)
> > > 
> > >      The main detail here to be careful of is that lots of
> > >      people are fond of the simplicity of the 
> > >      /debug/tracing/ debug UI, so when we replace it we 
> > >      want to do it by keeping that simple workflow (or 
> > >      best by making it even simpler). I have a few ideas 
> > >      how to do this.
> > 
> > How? We can emulate the /debug/tracing result with something
> > like perf trace, still that won't replace the immediate
> > availability of the result of any trace, which makes it
> > valuable for any simplest workflows.
> 
> I'm a bit torn about this. I really like the availability of the ascii
> interface, but if we can come up with a very basic trace binary tool
> which can be built for deep embedded w/o requiring the world and some
> more libs to be available, then I might give up my resistance. Ideally
> it should be done so it can be easily integrated into busybox.
> 
> I don't care whether I do
> 
> echo 1 >/debug/..../XXX/enable
> cat /debug/tracing/trace
> 
> or
> 
> perfmini trace enable XXX
> perfmini trace dump

My suggestion for that flow is even shorter:

  trace --enable XXX
  trace

Plus:

  trace --list
  trace --enable
  trace --disable

> as long as the tool is built in a way that it does not 
> need updates when we add trace points or other 
> functionality to the kernel.

Yeah, most definitely. The sysfs event_source class will 
ensure that whatever (new) events are available propagate 
through the tool and are available to it.

Thanks,

	Ingo

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