linux-kernel - Re: [RFD] Future tracing/instrumentation directions

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Message-ID: <20100520114218.GA15531@elte.hu>
Date:	Thu, 20 May 2010 13:42:18 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Christoph Hellwig <hch@....de>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Li Zefan <lizf@...fujitsu.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Johannes Berg <johannes.berg@...el.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Tom Zanussi <tzanussi@...il.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andi Kleen <andi@...stfloor.org>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Lin Ming <ming.m.lin@...el.com>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	Mike Galbraith <efault@....de>,
	Paul Mackerras <paulus@...ba.org>,
	Hitoshi Mitake <mitake@....info.waseda.ac.jp>,
	Robert Richter <robert.richter@....com>
Subject: Re: [RFD] Future tracing/instrumentation directions


* Thomas Gleixner <tglx@...utronix.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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