Commit 83e3c487 authored by Kirill A. Shutemov's avatar Kirill A. Shutemov Committed by Ingo Molnar

mm/sparsemem: Allocate mem_section at runtime for CONFIG_SPARSEMEM_EXTREME=y

Size of the mem_section[] array depends on the size of the physical address space.

In preparation for boot-time switching between paging modes on x86-64
we need to make the allocation of mem_section[] dynamic, because otherwise
we waste a lot of RAM: with CONFIG_NODE_SHIFT=10, mem_section[] size is 32kB
for 4-level paging and 2MB for 5-level paging mode.

The patch allocates the array on the first call to sparse_memory_present_with_active_regions().
Signed-off-by: default avatarKirill A. Shutemov <>
Cc: Andrew Morton <>
Cc: Andy Lutomirski <>
Cc: Borislav Petkov <>
Cc: Cyrill Gorcunov <>
Cc: Linus Torvalds <>
Cc: Peter Zijlstra <>
Cc: Thomas Gleixner <>
Link: default avatarIngo Molnar <>
parent 96753522
......@@ -1150,13 +1150,17 @@ struct mem_section {
extern struct mem_section *mem_section[NR_SECTION_ROOTS];
extern struct mem_section **mem_section;
extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT];
static inline struct mem_section *__nr_to_section(unsigned long nr)
if (!mem_section)
return NULL;
if (!mem_section[SECTION_NR_TO_ROOT(nr)])
return NULL;
return &mem_section[SECTION_NR_TO_ROOT(nr)][nr & SECTION_ROOT_MASK];
......@@ -5646,6 +5646,16 @@ void __init sparse_memory_present_with_active_regions(int nid)
unsigned long start_pfn, end_pfn;
int i, this_nid;
if (!mem_section) {
unsigned long size, align;
size = sizeof(struct mem_section) * NR_SECTION_ROOTS;
mem_section = memblock_virt_alloc(size, align);
for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, &this_nid)
memory_present(this_nid, start_pfn, end_pfn);
......@@ -22,8 +22,7 @@
* 1) mem_section - memory sections, mem_map's for valid memory
struct mem_section *mem_section[NR_SECTION_ROOTS]
struct mem_section **mem_section;
struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT]
......@@ -100,7 +99,7 @@ static inline int sparse_index_init(unsigned long section_nr, int nid)
int __section_nr(struct mem_section* ms)
unsigned long root_nr;
struct mem_section* root;
struct mem_section *root = NULL;
for (root_nr = 0; root_nr < NR_SECTION_ROOTS; root_nr++) {
root = __nr_to_section(root_nr * SECTIONS_PER_ROOT);
......@@ -111,7 +110,7 @@ int __section_nr(struct mem_section* ms)
return (root_nr * SECTIONS_PER_ROOT) + (ms - root);
......@@ -329,11 +328,17 @@ sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat,
static void __init check_usemap_section_nr(int nid, unsigned long *usemap)
unsigned long usemap_snr, pgdat_snr;
static unsigned long old_usemap_snr = NR_MEM_SECTIONS;
static unsigned long old_pgdat_snr = NR_MEM_SECTIONS;
static unsigned long old_usemap_snr;
static unsigned long old_pgdat_snr;
struct pglist_data *pgdat = NODE_DATA(nid);
int usemap_nid;
/* First call */
if (!old_usemap_snr) {
old_usemap_snr = NR_MEM_SECTIONS;
old_pgdat_snr = NR_MEM_SECTIONS;
usemap_snr = pfn_to_section_nr(__pa(usemap) >> PAGE_SHIFT);
pgdat_snr = pfn_to_section_nr(__pa(pgdat) >> PAGE_SHIFT);
if (usemap_snr == pgdat_snr)
Markdown is supported
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment