From f2fc10e0b3fe7d1aecbd2cab6bf0007b6771e16d Mon Sep 17 00:00:00 2001 From: Baoquan He Date: Fri, 17 Aug 2018 15:48:38 -0700 Subject: [PATCH] mm/sparse.c: add a static variable nr_present_sections Patch series "mm/sparse: Optimize memmap allocation during sparse_init()", v6. 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. This patch (of 5): nr_present_sections is used to record how many memory sections are marked as present during system boot up, and will be used in the later patch. Link: http://lkml.kernel.org/r/20180228032657.32385-2-bhe@redhat.com Signed-off-by: Baoquan He Acked-by: Dave Hansen Reviewed-by: Andrew Morton Reviewed-by: Pavel Tatashin Reviewed-by: Oscar Salvador Cc: Pasha Tatashin Cc: Kirill A. Shutemov Cc: Pankaj Gupta Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/sparse.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/mm/sparse.c b/mm/sparse.c index b1b14a9..99a6383 100644 --- a/mm/sparse.c +++ b/mm/sparse.c @@ -200,6 +200,12 @@ static inline int next_present_section_nr(int section_nr) (section_nr <= __highest_present_section_nr)); \ section_nr = next_present_section_nr(section_nr)) +/* + * Record how many memory sections are marked as present + * during system bootup. + */ +static int __initdata nr_present_sections; + /* Record a memory area against a node. */ void __init memory_present(int nid, unsigned long start, unsigned long end) { @@ -229,6 +235,7 @@ void __init memory_present(int nid, unsigned long start, unsigned long end) ms->section_mem_map = sparse_encode_early_nid(nid) | SECTION_IS_ONLINE; section_mark_present(ms); + nr_present_sections++; } } } -- 2.7.4