On Fri, Apr 01, 2022 at 10:22:00PM +0000, Song Liu wrote: > >> Please fix the underlying issues instead of papering over them and > >> creating a huge maintainance burden for others. > > After reading the code a little more, I wonder what would be best strategy. > IIUC, most of the kernel is not ready for huge page backed vmalloc memory. > For example, all the module_alloc cannot work with huge pages at the moment. > And the error Paul Menzel reported in drm_fb_helper.c will probably hit > powerpc with 5.17 kernel as-is? (trace attached below) > > Right now, we have VM_NO_HUGE_VMAP to let a user to opt out of huge pages. > However, given there are so many users of vmalloc, vzalloc, etc., we > probably do need a flag for the user to opt-in? > > Does this make sense? Any recommendations are really appreciated. I think there is multiple aspects here: - if we think that the kernel is not ready for hugepage backed vmalloc in general we need to disable it in powerpc for now. - if we think even in the longer run only some users can cope with hugepage backed vmalloc we need to turn it into an opt-in in general and not just for x86 - there still to appear various unresolved underlying x86 specific issues that need to be fixed either way
