On Sun, Jan 02, 2022 at 10:57:35PM +0100, Ingo Molnar wrote: > > I'm pleased to announce the first public version of my new "Fast Kernel > Headers" project that I've been working on since late 2020, which is a > comprehensive rework of the Linux kernel's header hierarchy & header > dependencies, with the dual goals of: > > - speeding up the kernel build (both absolute and incremental build times) > > - decoupling subsystem type & API definitions from each other > > The fast-headers tree consists of over 25 sub-trees internally, spanning > over 2,200 commits, which can be found here: > > git://git.kernel.org/pub/scm/linux/kernel/git/mingo/tip.git master > > As most kernel developers know, there's around ~10,000 main .h headers in > the Linux kernel, in the include/ and arch/*/include/ hierarchies. Over the > last 30+ years they have grown into a complicated & painful set of > cross-dependencies we are affectionately calling 'Dependency Hell'. $ git grep -n -w kernel.h mingo/sched/headers -- include/ | wc -l 138 $ git grep -n -w kernel.h next/master -- include/ | wc -l 96 Can we rather split kernel.h more? In some cases kernel.h is used just as a bundle instead of ~2-3 headers. And I can't get why kernel.h is returned in the drm headers. AFAICT there are no dependencies: mingo/sched/headers:include/drm/drm_gem_ttm_helper.h:6:#include <linux/kernel.h> mingo/sched/headers:include/drm/drm_gem_vram_helper.h:15:#include <linux/kernel.h> /* for container_of() */ mingo/sched/headers:include/drm/drm_mm.h:44:#include <linux/kernel.h> mingo/sched/headers:include/drm/drm_property.h:28:#include <linux/kernel.h> mingo/sched/headers:include/drm/intel-gtt.h:9:#include <linux/kernel.h> Ah, it may be due to base on the vanilla rather than on next, it would be nice to see this rebased on top of v5.17-rc1 when it's out. -- With Best Regards, Andy Shevchenko
