This is v2 post. V1 can be found here: https://www.spinics.net/lists/linux-mm/msg144486.html In sparse_init(), two temporary pointer arrays, usemap_map and map_map are allocated with the size of NR_MEM_SECTIONS. They are used to store each memory section's usemap and mem map if marked as present. In 5-level paging mode, this will cost 512M memory though they will be released at the end of sparse_init(). System with few memory, like kdump kernel which usually only has about 256M, will fail to boot because of allocation failure if CONFIG_X86_5LEVEL=y. In this patchset, optimize the memmap allocation code to only use usemap_map and map_map with the size of nr_present_sections. This makes kdump kernel boot up with normal crashkernel='' setting when CONFIG_X86_5LEVEL=y. Baoquan He (3): mm/sparse: Add a static variable nr_present_sections mm/sparsemem: Defer the ms->section_mem_map clearing mm/sparse: Optimize memmap allocation during sparse_init() mm/sparse-vmemmap.c | 9 +++++---- mm/sparse.c | 54 +++++++++++++++++++++++++++++++++++------------------ 2 files changed, 41 insertions(+), 22 deletions(-) -- 2.13.6 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
