On Fri, Aug 17, 2012 at 10:39:39AM -0400, Steven Rostedt wrote: > On Fri, 2012-08-17 at 11:04 -0300, Ezequiel Garcia wrote: > > On Fri, Aug 17, 2012 at 10:55 AM, Steven Rostedt <rost...@goodmis.org> > > wrote: > > > On Fri, 2012-08-17 at 08:01 -0300, Ezequiel Garcia wrote: > > > > > >> Regarding the 'complete solution': to be able to capture events from > > >> the very beggining... > > >> Have you thought about this? > > >> Could you give me a hint on how could I implement it? > > > > > > How far in the "beginning"? Before memory is set up? > > > > Yes. > > > > > I wouldn't do that. > > > > Yeah, perhaps it sounds crazy. It makes some sense for kmem events, though. > > It doesn't sound crazy, because I've done it before. There may be ways > to do it. > > > > > > I have in the past (set up before memory was finished being > > > initialized), but things have changed since then. > > > > > > One thing that we could do for those that want really early tracing, is > > > to add a config option to add a static temporary ring buffer, that gets > > > > Yes, something like this would be ideal. How would this ring buffer be > > allocated? > > Perhaps as static and __initdata? > > Yes. > > > This way it would be released afterwards, right? > > Correct. > > > > > > copied into the default ring buffer after memory is set up. That may be > > > the easiest way. > > > > > > Once memory is set up, the ring buffer can be allocated and events can > > > be traced, but the ring buffer needs to be set up first. All it would > > > take is some calls in init/main.c start_kernel() to the initialization. > > > > > > > Note that my main concern is on trace_events (kmem events to be precise). > > However this are registered through tracepoints and in turn this tracepoints > > depend on kmalloc and friends. So, right now is a chicken-egg problem. > > I don't think kmalloc is the issue. The big problem in front of you is > jump labels. That's what enables and disables trace points, and it gets > initialized just after memory is set up. You may have to force jump > labels off when doing early tracing :-/ Although I'm not sure it > requires allocations. >
The only allocation jump labels should do is when modules are loaded. So I think you should be able to move them earlier, if need be. Thanks, -Jason -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
