On Fri 04-01-19 10:25:12, Qian Cai wrote: > On 1/4/19 10:17 AM, Michal Hocko wrote: > > 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? > > Yes, a proof-of-concept version is v1 where ends up with more ifdefs due to > dealing with all the low-level details, > > https://lore.kernel.org/lkml/20181220060303.38686-1-cai@xxxxxx/ That is obviously not what I've had in mind. We have __init_single_page which initializes a single struct page. Is there any way to hook page_ext initialization there? -- Michal Hocko SUSE Labs
