On Fri 04-01-19 10:01:40, Qian Cai wrote: > On 1/4/19 8:09 AM, Michal Hocko wrote: > >> Here is the number without DEFERRED_STRUCT_PAGE_INIT. > >> > >> == page_ext_init() after page_alloc_init_late() == > >> Node 0, zone DMA: page owner found early allocated 0 pages > >> Node 0, zone DMA32: page owner found early allocated 7009 pages > >> Node 0, zone Normal: page owner found early allocated 85827 pages > >> Node 4, zone Normal: page owner found early allocated 75063 pages > >> > >> == page_ext_init() before kmemleak_init() == > >> Node 0, zone DMA: page owner found early allocated 0 pages > >> Node 0, zone DMA32: page owner found early allocated 6654 pages > >> Node 0, zone Normal: page owner found early allocated 41907 pages > >> Node 4, zone Normal: page owner found early allocated 41356 pages > >> > >> So, it told us that it will miss tens of thousands of early page allocation call > >> sites. > > > > This is an answer for the first part of the question (how much). The > > second is _do_we_care_? > > Well, the purpose of this simple "ugly" ifdef is to avoid a regression for the > existing page_owner users with DEFERRED_STRUCT_PAGE_INIT deselected that would > start to miss tens of thousands early page allocation call sites. I am pretty sure we will hear about that when that happens. And act accordingly. > The other option I can think of to not hurt your eyes is to rewrite the whole > page_ext_init(), init_page_owner(), init_debug_guardpage() to use all early > functions, so it can work in both with DEFERRED_STRUCT_PAGE_INIT=y and without. > However, I have a hard-time to convince myself it is a sensible thing to do. Or simply make the page_owner initialization only touch the already initialized memory. Have you explored that option as well? Look, I am trying to push for a clean solution. Hacks I have seen so far are not convincing. You have identified a regression and as such I would consider the most straightforward to revert the buggy commit. If you want to improve the situation then I would suggest to think about something that is more robust than ifdefed hacks. It might be more work but it also might be a better thing long term. If you think I am asking too much then you are free to ignore my opinion. I am not a maintainer of the page_owner code. -- Michal Hocko SUSE Labs
