On Wed, Jan 16, 2019 at 02:47:16PM +0100, Christophe Leroy wrote: > Le 16/01/2019 à 14:18, Matthew Wilcox a écrit : > > I disagree with your objective. Making more code common is a great idea, > > but this patch is too unambitious. We should be heading towards one or > > two page table allocation functions instead of having every architecture do > > its own thing. > > > > So start there. Move the x86 function into common code and convert one > > other architecture to use it too. > > Are we talking about pte_alloc_one_kernel() and pte_alloc_one() ? > > I'm not sure x86 function is the best common one, as it seems to allocate a > multiple of PAGE_SIZE only. And that's the common case. Most architectures use a single page for at least one level of the pte/pmd/pud/p4d/pgd hierarchy. Some use multiple pages and some use a fraction of a page. > Some arches like powerpc use pagetables which are smaller than a page, for > instance powerpc 8xx uses 4k pagetables even with 16k pages, which means a > single page can be used by 4 pagetables. Those can be added later. Note I said "one or two", and that's what I had in mind; I think we want one function that allocates just a page and another that allocates a page fragment. Then we can have a good discussion about what method we use; s390 and ppc use different techniques today and there's really no good reason for that.
