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SubjectRe: [PATCH 3/3] tracing/function-return-tracer: add the overrun field

On Tue, 18 Nov 2008, Ingo Molnar wrote:

>
> * Steven Rostedt <rostedt@goodmis.org> wrote:
>
> >
> > On Tue, 18 Nov 2008, Ingo Molnar wrote:
> > > >
> > > > Ok I will try with 50. If there are still a lot and often missing
> > > > traces with this depth, perhaps should we consider a hybrid solution
> > > > between ret stack and trampolines? We could use the normal ret stack
> > > > on struct info for most common cases and the trampoline when we are
> > > > exceeding the depth....
> > >
> > > dunno, trampolines make me feel uneasy.
> > >
> > > Could you set it to some really large value (200) and add a "max
> > > depth seen" variable perhaps, and see the maximum depth?
> >
> > Don't run that on a box you care about ;-) But hopefully the stacks
> > will not collide. This should also depend on IRQSTACKS.
>
> that reminds me: ti->ret_stack[] should be moved to task->ret_stack[].
> That way we decouple its size from any kernel stack size limits.
> (thread-info resides at one end of the kernel stack, on x86)

Yeah, I recommended that to Frederic to save space. But that can be
dangerous. Using task instead would be safer with the downside of making
the task struct even bigger.

-- Steve



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