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. 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.
