Messages in this thread | | | Date | Wed, 17 Nov 2010 14:43:02 +0100 | From | Frederic Weisbecker <> | Subject | Re: [ANNOUNCE] New utility: 'trace' |
| |
On Wed, Nov 17, 2010 at 02:36:16PM +0100, Peter Zijlstra wrote: > On Wed, 2010-11-17 at 14:10 +0100, Ingo Molnar wrote: > > * Peter Zijlstra <peterz@infradead.org> wrote: > > > > > On Wed, 2010-11-17 at 13:53 +0100, Frederic Weisbecker wrote: > > > > On Wed, Nov 17, 2010 at 12:35:50PM +0100, Peter Zijlstra wrote: > > > > > On Wed, 2010-11-17 at 09:30 +0100, Ingo Molnar wrote: > > > > > > > For example I'm currently working with dozens of trace_printk() and I would be > > > > > > > very happy to turn some of them off half of the time. > > > > > > > > > > > > I guess we could try such a patch. If you send a prototype i'd be interested in > > > > > > testing it out. > > > > > > > > > > I don't see the point, the kernel shouldn't contain any trace_printk()s > > > > > to begin with.. > > > > > > > > > > > > It's oriented toward developers. Those who use dozens of tracepoints in > > > > their tree because they are debugging something or developing a new feature, > > > > they might to deactivate/reactivate some of these independant points. > > > > > > > > This can also apply to dynamic_printk of course. > > > > > > > > Well, the very first and main point is to standardize trace_printk into > > > > a trace event so that it gets usable by perf tools. I have been asked many > > > > times "how to use trace_printk() with perf?". > > > > > > Thing is, since its these dev who add the trace_printk()s to begin with, I don't > > > see the point in splitting them out, if you didn't want them why did you add them > > > to begin with?! > > > > That's a common workflow: lots of printks (trace_printk's) put all around the code - > > and sometimes one set of tracepoints is needed, one time another set. > > > > _If_ we succeed in presenting them like Frederic suggested it, and if we make the > > turning on/off _simpler_ (no kernel modification) and faster (no kernel reboot) via > > the tooling, people like Frederic might start using it. > > > > I dont think we should fight the workflow itself - it makes sense. > > > > The only question is whether we can represent it all in a nicer fashion than 'modify > > the source code and reboot'. If we cannot then there's no point - but i'm not sure > > about it and Frederic seems to be convinced too that he can make such a switch > > on/off facility intuitive. We'll only see if we try it. > > > > Also, i dont see any harm - do you? > > Yes, trace_printk() is a pure debug interface, solely meant for the edit > + reboot cycle.
So why prevent from making it even more handy?
> If you want anything more than that we've got tracepoints. The rule up > until now has been to never merge a trace_printk() user.
Sure, that doesn't change the core idea of trace_prink(): none of them must be merged. That new event interface would just make private uses of trace_printk() more convenient.
| |