Re: [BUG] msr-trace.h:42 suspicious rcu_dereference_check() usage!

[Andi Kleen]

> And a popf can be much more expensive than any of these. You should
> know, not all instructions are equal.
> 
> Using perf, I've seen popf take up almst 30% of a function the size of
> this.

In any case it's a small fraction of the 600+ instructions which are currently
executed for every enabled trace point.

If ftrace was actually optimized code this would make some sense, but it
clearly isn't ...

-Andi