On 11/10/2018 09:10 AM, Peter Zijlstra wrote: > On Fri, Nov 09, 2018 at 09:04:12AM +0100, Ingo Molnar wrote: >> BTW., if you are interested in more radical approaches to optimize >> lockdep, we could also add a static checker via objtool driven call graph >> analysis, and mark those locks terminal that we can prove are terminal. >> >> This would require the unified call graph of the kernel image and of all >> modules to be examined in a final pass, but that's within the principal >> scope of objtool. (This 'final pass' could also be done during bootup, at >> least in initial versions.) > Something like this is needed for objtool LTO support as well. I just > dread the build time 'regressions' this will introduce :/ > > The final link pass is already by far the most expensive part (as > measured in wall-time) of building a kernel, adding more work there > would really suck :/ I think the idea is to make objtool have the capability to do that. It doesn't mean we need to turn it on by default in every build. Cheers, Longman
