Hi Pavel, On 06/27/18 at 01:47pm, Pavel Tatashin wrote: > This work made me think why do we even have > CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER ? This really should be the > default behavior for all systems. Yet, it is enabled only on x86_64. > We could clean up an already messy sparse.c if we removed this config, > and enabled its path for all arches. We would not break anything > because if we cannot allocate one large mmap_map we still fallback to > allocating a page at a time the same as what happens when > CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER=n. Thanks for your idea. Seems the common ARCHes all have ARCH_SPARSEMEM_ENABLE, such as x86, arm/64, power, s390, mips, others don't have. For them, removing CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER makes sense. I will make a clean up patch to do this, but I can only test it on x86. If test robot or other issues report issue on this clean up patch, Andrew can help only pick the current 4 patches after updating, then we can continue discussing the clean up patch. From the current code, it should be OK to all ARCHes. Thanks Baoquan
