Messages in this thread | | | Date | Tue, 5 Jan 2010 07:05:37 +0100 | From | Ingo Molnar <> | Subject | Re: [RFC PATCH] dynamic debug - adding ring buffer storage support |
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* Frederic Weisbecker <fweisbec@gmail.com> wrote:
> 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.
Yeah - but it's only really useful if we could properly encode/extract the record format as well.
The one person's printk would become another person's programmable tracepoint.
> Too bad that would bloat the memory.
Should be optional of course, and then developers/distros pick instrumentation landscape winners/losers. To most people memory overhead is not a big issue, if the result is sufficiently useful.
Ingo
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