On 17 Nov 2020, at 16:22, Matthew Wilcox wrote: > On Tue, Nov 17, 2020 at 04:12:03PM -0500, Zi Yan wrote: >> On 17 Nov 2020, at 16:05, Matthew Wilcox wrote: >> >>> On Fri, Nov 13, 2020 at 05:38:01PM -0800, Roman Gushchin wrote: >>>> On Fri, Nov 13, 2020 at 08:08:58PM -0500, Zi Yan wrote: >>>>> Matthew recently converted split_page_owner to take nr instead of order.[1] >>>>> But I am not >>>>> sure why, since it seems to me that two call sites (__split_huge_page in >>>>> mm/huge_memory.c and split_page in mm/page_alloc.c) can pass the order >>>>> information. >>>> >>>> Yeah, I'm not sure why too. Maybe Matthew has some input here? >>>> You can also pass new_nr, but IMO orders look so much better here. >>> >>> If only I'd written that information in the changelog ... oh wait, I did! >>> >>> mm/page_owner: change split_page_owner to take a count >>> >>> The implementation of split_page_owner() prefers a count rather than the >>> old order of the page. When we support a variable size THP, we won't >>> have the order at this point, but we will have the number of pages. >>> So change the interface to what the caller and callee would prefer. >> >> There are two callers, split_page in mm/page_alloc.c and __split_huge_page in >> mm/huge_memory.c. The former has the page order. The latter has the page order >> information before __split_huge_page_tail is called, so we can do >> old_order = thp_order(head) instead of nr = thp_nr_page(head) and use old_order. >> What am I missing there? > > Sure, we could also do that. But what I wrote was true at the time I > wrote it. Got it. Thanks. Will change it to use old_order to make split_page_owner parameters look more consistent. — Best Regards, Yan Zi
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