Commit aa888a74 authored by Andi Kleen's avatar Andi Kleen Committed by Linus Torvalds
Browse files

hugetlb: support larger than MAX_ORDER

This is needed on x86-64 to handle GB pages in hugetlbfs, because it is
not practical to enlarge MAX_ORDER to 1GB.

Instead the 1GB pages are only allocated at boot using the bootmem
allocator using the hugepages=...  option.

These 1G bootmem pages are never freed.  In theory it would be possible to
implement that with some complications, but since it would be a one-way
street (>= MAX_ORDER pages cannot be allocated later) I decided not to

The >= MAX_ORDER code is not ifdef'ed per architecture.  It is not very
big and the ifdef uglyness seemed not be worth it.

Known problems: /proc/meminfo and "free" do not display the memory
allocated for gb pages in "Total".  This is a little confusing for the
Acked-by: default avatarAndrew Hastings <>
Signed-off-by: default avatarAndi Kleen <>
Signed-off-by: default avatarNick Piggin <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 01ad1c08
......@@ -14,6 +14,7 @@
#include <linux/mempolicy.h>
#include <linux/cpuset.h>
#include <linux/mutex.h>
#include <linux/bootmem.h>
#include <linux/sysfs.h>
#include <asm/page.h>
......@@ -489,7 +490,7 @@ static void free_huge_page(struct page *page)
if (h->surplus_huge_pages_node[nid]) {
if (h->surplus_huge_pages_node[nid] && huge_page_order(h) < MAX_ORDER) {
update_and_free_page(h, page);
......@@ -550,6 +551,9 @@ static struct page *alloc_fresh_huge_page_node(struct hstate *h, int nid)
struct page *page;
if (h->order >= MAX_ORDER)
return NULL;
page = alloc_pages_node(nid,
......@@ -616,6 +620,9 @@ static struct page *alloc_buddy_huge_page(struct hstate *h,
struct page *page;
unsigned int nid;
if (h->order >= MAX_ORDER)
return NULL;
* Assume we will successfully allocate the surplus page to
* prevent racing processes from causing the surplus to exceed
......@@ -792,6 +799,10 @@ static void return_unused_surplus_pages(struct hstate *h,
/* Uncommit the reservation */
h->resv_huge_pages -= unused_resv_pages;
/* Cannot return gigantic pages currently */
if (h->order >= MAX_ORDER)
nr_pages = min(unused_resv_pages, h->surplus_huge_pages);
while (remaining_iterations-- && nr_pages) {
......@@ -913,6 +924,63 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
return page;
static __initdata LIST_HEAD(huge_boot_pages);
struct huge_bootmem_page {
struct list_head list;
struct hstate *hstate;
static int __init alloc_bootmem_huge_page(struct hstate *h)
struct huge_bootmem_page *m;
int nr_nodes = nodes_weight(node_online_map);
while (nr_nodes) {
void *addr;
addr = __alloc_bootmem_node_nopanic(
huge_page_size(h), huge_page_size(h), 0);
if (addr) {
* Use the beginning of the huge page to store the
* huge_bootmem_page struct (until gather_bootmem
* puts them into the mem_map).
m = addr;
if (m)
goto found;
return 0;
BUG_ON((unsigned long)virt_to_phys(m) & (huge_page_size(h) - 1));
/* Put them into a private list first because mem_map is not up yet */
list_add(&m->list, &huge_boot_pages);
m->hstate = h;
return 1;
/* Put bootmem huge pages into the standard lists after mem_map is up */
static void __init gather_bootmem_prealloc(void)
struct huge_bootmem_page *m;
list_for_each_entry(m, &huge_boot_pages, list) {
struct page *page = virt_to_page(m);
struct hstate *h = m->hstate;
WARN_ON(page_count(page) != 1);
prep_compound_page(page, h->order);
prep_new_huge_page(h, page, page_to_nid(page));
static void __init hugetlb_init_one_hstate(struct hstate *h)
unsigned long i;
......@@ -923,7 +991,10 @@ static void __init hugetlb_init_one_hstate(struct hstate *h)
h->hugetlb_next_nid = first_node(node_online_map);
for (i = 0; i < h->max_huge_pages; ++i) {
if (!alloc_fresh_huge_page(h))
if (h->order >= MAX_ORDER) {
if (!alloc_bootmem_huge_page(h))
} else if (!alloc_fresh_huge_page(h))
h->max_huge_pages = h->free_huge_pages = h->nr_huge_pages = i;
......@@ -956,6 +1027,9 @@ static void try_to_free_low(struct hstate *h, unsigned long count)
int i;
if (h->order >= MAX_ORDER)
for (i = 0; i < MAX_NUMNODES; ++i) {
struct page *page, *next;
struct list_head *freel = &h->hugepage_freelists[i];
......@@ -982,6 +1056,9 @@ static unsigned long set_max_huge_pages(struct hstate *h, unsigned long count)
unsigned long min_count, ret;
if (h->order >= MAX_ORDER)
return h->max_huge_pages;
* Increase the pool size
* First take pages out of surplus state. Then make up the
......@@ -1210,6 +1287,8 @@ static int __init hugetlb_init(void)
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