Hi, There is a lot of similar and duplicated code in architecture specific bits of memory management. For instance, as it was recently discussed at [1], most architectures have #define GFP_KERNEL | __GFP_ZERO for allocating page table pages and many of them use similar, if not identical, implementation of pte_alloc_one*(). But that's only the tip of the iceberg. I've seen several early_alloc() or similarly called routines that do if (slab_is_available()) return kazalloc() else return memblock_alloc() Some other trivial examples are free_initmem(), free_initrd_mem() and, to some extent, mem_init(), but more generally there are a lot of similarities in arch/*/mm/. More complex cases are per-cpu initialization, passing of memory topology to the generic MM, reservation of crash kernel, mmap of vdso etc. They are not really duplicated, but still are very similar in at least several architectures. While factoring out the common code is an obvious step to take, I believe there is also room for refining arch <-> mm interface to avoid adding extra HAVE_ARCH_NO_BOOTMEM^w^wWHAT_NOT and then searching for ways to get rid of them. This is particularly true for mm initialization. It evolved the way it's evolved, but now we can step back to black/white board and consider design that hopefully will avoid problems like [2]. As a side note, it might be also worth looking into dropping DISCONTIGMEM, although Kconfig still recommends to prefer it over SPARSEMEM [3]. [1] https://lore.kernel.org/lkml/1547619692-7946-1-git-send-email-anshuman.khandual@xxxxxxx/ [2] https://lore.kernel.org/lkml/20190114082416.30939-1-mhocko@xxxxxxxxxx/ [3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/mm/Kconfig#n49 -- Sincerely yours, Mike.
