On Fri, Aug 16, 2019 at 12:13:59PM +0200, Vlastimil Babka wrote: > Currently, page owner info is only recorded for the first page of a high-order > allocation, and copied to tail pages in the event of a split page. With the > plan to keep previous owner info after freeing the page, it would be benefical > to record page owner for each subpage upon allocation. This increases the > overhead for high orders, but that should be acceptable for a debugging option. > > The order stored for each subpage is the order of the whole allocation. This > makes it possible to calculate the "head" pfn and to recognize "tail" pages > (quoted because not all high-order allocations are compound pages with true > head and tail pages). When reading the page_owner debugfs file, keep skipping > the "tail" pages so that stats gathered by existing scripts don't get inflated. > > Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx> Hm. That's all reasonable, but I have a question: do you see how page owner thing works for THP now? I don't see anything in split_huge_page() path (do not confuse it with split_page() path) that would copy the information to tail pages. Do you? -- Kirill A. Shutemov
