Re: tracepoint maintainance models

[Ingo Molnar <mingo@elte.hu>]

* Frank Ch. Eigler <fche@redhat.com> wrote:

> > I think your implementation is questionable if it causes any kind of 
> > jumps and conditions, even marked unlikely. Just put the needed data 
> > in a seperate section which can be used by the debugging tools. 
> > [...] No need to actually mess with the code for the usual cases.
> 
> Trouble is that it is specifically the *unusual* cases that need 
> compiler assistance via static markers, otherwise we'd manage with 
> just k/djprobes & debuginfo type efforts.

i think it's all fine as long as it's just a single 5-byte NOP that we 
are inserting - because in the *usual* case the 'parameter access 
side-effects' should have no effect. They will have an effect in the 
*unusual* case though, but that's very much by design - and it's not a 
performance issue because it's 1) unusual, 2) at most means a bit 
different code organization by gcc. It very likely wont mean any extra 
branches even in the unusual case. Or do i underestimate the scope of 
the problem? ;-)

	Ingo