On some architectures, the vmemmap areas use huge page mapping.
If we want to free the unused vmemmap pages, we have to split
the huge pmd firstly. So we should pre-allocate pgtable to split
huge pmd.
Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
---
include/linux/hugetlb.h | 17 ++++++
mm/hugetlb.c | 117 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 134 insertions(+)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index eed3dd3bd626..ace304a6196c 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -593,6 +593,23 @@ static inline unsigned int blocks_per_huge_page(struct hstate *h)
#include <asm/hugetlb.h>
+#ifdef CONFIG_HUGETLB_PAGE_FREE_VMEMMAP
+#ifndef arch_vmemmap_support_huge_mapping
+static inline bool arch_vmemmap_support_huge_mapping(void)
+{
+ return false;
+}
+#endif
+
+#ifndef VMEMMAP_HPAGE_SHIFT
+#define VMEMMAP_HPAGE_SHIFT PMD_SHIFT
+#endif
+#define VMEMMAP_HPAGE_ORDER (VMEMMAP_HPAGE_SHIFT - PAGE_SHIFT)
+#define VMEMMAP_HPAGE_NR (1 << VMEMMAP_HPAGE_ORDER)
+#define VMEMMAP_HPAGE_SIZE ((1UL) << VMEMMAP_HPAGE_SHIFT)
+#define VMEMMAP_HPAGE_MASK (~(VMEMMAP_HPAGE_SIZE - 1))
+#endif /* CONFIG_HUGETLB_PAGE_FREE_VMEMMAP */
+
#ifndef is_hugepage_only_range
static inline int is_hugepage_only_range(struct mm_struct *mm,
unsigned long addr, unsigned long len)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index f1b2b733b49b..d6ae9b6876be 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1295,11 +1295,108 @@ static inline void destroy_compound_gigantic_page(struct page *page,
#ifdef CONFIG_HUGETLB_PAGE_FREE_VMEMMAP
#define RESERVE_VMEMMAP_NR 2U
+#define page_huge_pte(page) ((page)->pmd_huge_pte)
+
static inline unsigned int nr_free_vmemmap(struct hstate *h)
{
return h->nr_free_vmemmap_pages;
}
+static inline unsigned int nr_vmemmap(struct hstate *h)
+{
+ return nr_free_vmemmap(h) + RESERVE_VMEMMAP_NR;
+}
+
+static inline unsigned long nr_vmemmap_size(struct hstate *h)
+{
+ return (unsigned long)nr_vmemmap(h) << PAGE_SHIFT;
+}
+
+static inline unsigned int nr_pgtable(struct hstate *h)
+{
+ unsigned long vmemmap_size = nr_vmemmap_size(h);
+
+ if (!arch_vmemmap_support_huge_mapping())
+ return 0;
+
+ /*
+ * No need pre-allocate page tabels when there is no vmemmap pages
+ * to free.
+ */
+ if (!nr_free_vmemmap(h))
+ return 0;
+
+ return ALIGN(vmemmap_size, VMEMMAP_HPAGE_SIZE) >> VMEMMAP_HPAGE_SHIFT;
+}
+
+static inline void vmemmap_pgtable_init(struct page *page)
+{
+ page_huge_pte(page) = NULL;
+}
+
+static void vmemmap_pgtable_deposit(struct page *page, pte_t *pte_p)
+{
+ pgtable_t pgtable = virt_to_page(pte_p);
+
+ /* FIFO */
+ if (!page_huge_pte(page))
+ INIT_LIST_HEAD(&pgtable->lru);
+ else
+ list_add(&pgtable->lru, &page_huge_pte(page)->lru);
+ page_huge_pte(page) = pgtable;
+}
+
+static pte_t *vmemmap_pgtable_withdraw(struct page *page)
+{
+ pgtable_t pgtable;
+
+ /* FIFO */
+ pgtable = page_huge_pte(page);
+ if (unlikely(!pgtable))
+ return NULL;
+ page_huge_pte(page) = list_first_entry_or_null(&pgtable->lru,
+ struct page, lru);
+ if (page_huge_pte(page))
+ list_del(&pgtable->lru);
+ return page_to_virt(pgtable);
+}
+
+static int vmemmap_pgtable_prealloc(struct hstate *h, struct page *page)
+{
+ int i;
+ pte_t *pte_p;
+ unsigned int nr = nr_pgtable(h);
+
+ if (!nr)
+ return 0;
+
+ vmemmap_pgtable_init(page);
+
+ for (i = 0; i < nr; i++) {
+ pte_p = pte_alloc_one_kernel(&init_mm);
+ if (!pte_p)
+ goto out;
+ vmemmap_pgtable_deposit(page, pte_p);
+ }
+
+ return 0;
+out:
+ while (i-- && (pte_p = vmemmap_pgtable_withdraw(page)))
+ pte_free_kernel(&init_mm, pte_p);
+ return -ENOMEM;
+}
+
+static inline void vmemmap_pgtable_free(struct hstate *h, struct page *page)
+{
+ pte_t *pte_p;
+
+ if (!nr_pgtable(h))
+ return;
+
+ while ((pte_p = vmemmap_pgtable_withdraw(page)))
+ pte_free_kernel(&init_mm, pte_p);
+}
+
static void __init hugetlb_vmemmap_init(struct hstate *h)
{
unsigned int order = huge_page_order(h);
@@ -1323,6 +1420,15 @@ static void __init hugetlb_vmemmap_init(struct hstate *h)
static inline void hugetlb_vmemmap_init(struct hstate *h)
{
}
+
+static inline int vmemmap_pgtable_prealloc(struct hstate *h, struct page *page)
+{
+ return 0;
+}
+
+static inline void vmemmap_pgtable_free(struct hstate *h, struct page *page)
+{
+}
#endif
static void update_and_free_page(struct hstate *h, struct page *page)
@@ -1531,6 +1637,9 @@ void free_huge_page(struct page *page)
static void prep_new_huge_page(struct hstate *h, struct page *page, int nid)
{
+ /* Must be called before the initialization of @page->lru */
+ vmemmap_pgtable_free(h, page);
+
INIT_LIST_HEAD(&page->lru);
set_compound_page_dtor(page, HUGETLB_PAGE_DTOR);
set_hugetlb_cgroup(page, NULL);
@@ -1783,6 +1892,14 @@ static struct page *alloc_fresh_huge_page(struct hstate *h,
if (!page)
return NULL;
+ if (vmemmap_pgtable_prealloc(h, page)) {
+ if (hstate_is_gigantic(h))
+ free_gigantic_page(page, huge_page_order(h));
+ else
+ put_page(page);
+ return NULL;
+ }
+
if (hstate_is_gigantic(h))
prep_compound_gigantic_page(page, huge_page_order(h));
prep_new_huge_page(h, page, page_to_nid(page));
--
2.20.1
