Re: [RFD] Future tracing/instrumentation directions

From: Ingo Molnar
Date: Thu May 20 2010 - 07:43:13 EST

* Thomas Gleixner <tglx@xxxxxxxxxxxxx> 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 --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.


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