On Thu, Jun 01, 2017 at 08:08:24AM +0200, Ingo Molnar wrote: > > * Josh Poimboeuf <jpoim...@redhat.com> wrote: > > > Here's the contents of the undwarf.txt file which explains the 'why' in > > more detail: > > Ok, so the code quality looks pretty convincing to me - the new core > 'undwarf' > unwinder code is a _lot_ more readable than any of the Dwarf based attempts > before. > > That we control the debug info generation at build time is icing on the cake > to > me. > > One thing I'd like to see on the list of benefits side of the equation is a > size > comparison of kernel .text, with frame pointers vs. undwarf, on 64-bit > kernels.
Ok, will do a text size comparison. The only difficulty I encountered there is that the 'size' tool considers the .undwarf section to be text for some reason. So the "text" size grew considerably :-) > Being able to generate more optimal code in the hottest code paths of the > kernel > is the _real_, primary upstream kernel benefit of a different debuginfo > method - > which has to be weighed against the pain of introducing a new unwinder. But > this > submission does not talk about that aspect at all, which should be fixed I > think. Actually I devoted an entire one-sentence paragraph to performance in the documentation: The simpler debuginfo format also enables the unwinder to be relatively fast, which is important for perf and lockdep. But I'll try to highlight that a little more. -- Josh
