* Peter Zijlstra <pet...@infradead.org> wrote:
> On Wed, May 10, 2017 at 10:32:06AM +0200, Jiri Slaby wrote:
> > > But it does hurt, in the sense that the complicated format of DWARF CFI
> > > means the unwinder has to jump through a lot more hoops to read it.
> >
> > Why that matters, actually? Unwinder is nothing to be performance
> > oriented. And if somebody is doing a lot of unwinding during runtime,
> > they can switch to in-this-case-faster FP unwinder.
>
> perf (and ftrace) like the unwinder to be considered performance
> oriented.
Yes, and given how critical debugging is there's a kind of useful synergy here:
overall the perf unwinder is run about 10 orders of magnitude more often than
the
debugging unwinder, so it's a very big help in shaking out unwinder/debug-info
bugs and increasing robustness overall.
The 'price' for using the unwinder in perf is that it has to be fast.
Thanks,
Ingo
