Messages in this thread | | | Date | Tue, 18 Nov 2008 16:13:26 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 3/3] tracing/function-return-tracer: add the overrun field |
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* Steven Rostedt <rostedt@goodmis.org> wrote:
> > 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.
We almost never put new stuff into thread_info - we have the lockdep lock stack in the task structure too, for similar reasons.
Ingo
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