Re: CONFIG_FRAME_POINTER [was [PATCH] x86: BUILD_IRQ say .text]

[Hugh Dickins <hugh@veritas.com>]

On Mon, 28 Jul 2008, Ingo Molnar wrote:
> * Hugh Dickins <hugh@veritas.com> wrote:
> 
> > I rather think CONFIG_FRAME_POINTER shouldn't exist at all (or be a 
> > private, config-user-invisible, specific-to-a-few-arches thing): what 
> > one wants to configure is how far to sacrifice cpu performance and 
> > kernel smallness to getting a good stacktrace.  Frame pointer is just 
> > an implementation detail on that, appropriate to some arches. Perhaps 
> > three settings: no stacktrace, fair stacktrace, best stacktrace.
> 
> actually, we consciously use and rely on frame pointers on x86. The 
> runtime cost on 64-bit is miniscule and the improved backtrace output in 
> recent kernels makes backtraces _much_ easier to interpret:

Just to clarify, no way was I criticizing the use of frame pointers
on x86.  What I don't care for is that CONFIG_FRAME_POINTER is used
by common code (e.g. top level Makefile, and various debug Kconfigs),
when I see it as an arch-specific technique for getting best stacktrace.

Hugh