Messages in this thread | | | Date | Wed, 30 Dec 2009 23:50:13 +0100 | From | Frederic Weisbecker <> | Subject | Re: [RFC PATCH] dynamic debug - adding ring buffer storage support |
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On Mon, Dec 28, 2009 at 10:24:02AM +0100, Ingo Molnar wrote: > > that way you need to enable tracing as well... but thats ok I guess :) > > > > I was investigating trace events for this, but did not find a way > > to put variable length argument inside... and I overlooked the > > trace_printk, I'll look on it and see how it fits, thanks > > > > also having separate ring buffer makes the 'trace'/'trace_pipe' code > > really simple (suprissingly) compared to ftrace, and I thought > > on this place it could last for some time.. ;) > > I think what we want is a unified channel of events, of which printk (and > dynamic-printk) is one form. I.e. we should add printk events and > dynamic-printk events as well, which would show up in /debug/tracing/events/ > in a standard ftrace event form and would be accessible to tooling that way. > > For printk a single event would be enough i suspect (we dont want a separate > event for every printk), and for dynamic-printk we want to map the existing > dyn-printk topologies into /debug/tracing/events, to preserve the distinctions > and controls available there. > > This way in the long run we'd have one unified facility. > > Ingo
That said, I sometimes dream about one event per printk.
Having, say:
/debug/tracing/events/printk/ | ---- kernel/ | | | ------- time/ | | | | | ---- clocksource.c | | | | | --- clocksource_unstable:218/ | | | | | | | ---- format | | | | | | | ---- filter | | | | | | | ---- enable | | --- [...] | ------- [...] | ---- drivers/ | | | ---- [...] | ---- [...]
That would give a total control over every printk, trace_printk, etc...
Too bad that would bloat the memory. Well, that could be wrapped in a single, wildly implemented (understand: not using TRACE_EVENT macro) trace event, something able to walk through every calls of printk, trace_printk, early_printk, etc... and imitate a per printk event granularity.
But still it needs to be useful...
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