Re: [RFD] Future tracing/instrumentation directions

From: Frederic Weisbecker
Date: Thu May 20 2010 - 08:14:59 EST

On Thu, May 20, 2010 at 01:07:57PM +0200, Thomas Gleixner 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
> 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.
> Thanks,
> tglx

You have a (much) deeper experience than me about the embedded world.
And this was the area I worried most about, especially because dropping
the preformatted output means we add a random dependency.

If you think people can be fine a minimal tool that does this, then ok,
as far as the given tool is really easy to get and to build.

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