Re: [PATCH 0/2] ftrace: updates to tip

[Ingo Molnar <mingo@elte.hu>]

* Steven Rostedt <rostedt@goodmis.org> wrote:

> 
> On Fri, 16 Jan 2009, Ingo Molnar wrote:
> > > 
> > > But I do notice that not all functions produce a valid stack trace. 
> > > Maybe it would be better to add that api :-?
> > 
> > yes - i think that API would be more intuitive, and that way people could 
> > mix more interesting functions (with stack traces) with less important 
> > functions (no stack traces).
> 
> Ah, that's the point. We can't mix and match on these. Either all 
> functions that are traced do the stack trace, or none do. This is where 
> the new api may be confusing. [...]

that would be confusing indeed.

> [...] We can register a function to be traced via the function pointer, 
> and we can pick which functions to trace, but we can not separate out 
> different functions for different traces.

Why not? We could have a hash of all traced functions with metadata 
attached. Since patching functions in/out would be a relatively rare 
operation, this would be a highly efficient read-mostly hash.

	Ingo