All the infrastructure is ready, so we introduce nr_free_vmemmap_pages
field in the hstate to indicate how many vmemmap pages associated with
a HugeTLB page that can be freed to buddy allocator. And initialize it
in the hugetlb_vmemmap_init(). This patch is actual enablement of the
feature.
Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Acked-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Reviewed-by: Oscar Salvador <osalvador@xxxxxxx>
---
include/linux/hugetlb.h | 3 +++
mm/hugetlb.c | 1 +
mm/hugetlb_vmemmap.c | 30 ++++++++++++++++++++++++++----
mm/hugetlb_vmemmap.h | 5 +++++
4 files changed, 35 insertions(+), 4 deletions(-)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index ad249e56ac49..775aea53669a 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -560,6 +560,9 @@ struct hstate {
unsigned int nr_huge_pages_node[MAX_NUMNODES];
unsigned int free_huge_pages_node[MAX_NUMNODES];
unsigned int surplus_huge_pages_node[MAX_NUMNODES];
+#ifdef CONFIG_HUGETLB_PAGE_FREE_VMEMMAP
+ unsigned int nr_free_vmemmap_pages;
+#endif
#ifdef CONFIG_CGROUP_HUGETLB
/* cgroup control files */
struct cftype cgroup_files_dfl[7];
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 5518283aa667..04dde2b71f3e 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3220,6 +3220,7 @@ void __init hugetlb_add_hstate(unsigned int order)
h->next_nid_to_free = first_memory_node;
snprintf(h->name, HSTATE_NAME_LEN, "hugepages-%lukB",
huge_page_size(h)/1024);
+ hugetlb_vmemmap_init(h);
parsed_hstate = h;
}
diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index 224a3cb69bf9..36ebd677e606 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -208,13 +208,10 @@ early_param("hugetlb_free_vmemmap", early_hugetlb_free_vmemmap_param);
/*
* How many vmemmap pages associated with a HugeTLB page that can be freed
* to the buddy allocator.
- *
- * Todo: Returns zero for now, which means the feature is disabled. We will
- * enable it once all the infrastructure is there.
*/
static inline unsigned int free_vmemmap_pages_per_hpage(struct hstate *h)
{
- return 0;
+ return h->nr_free_vmemmap_pages;
}
static inline unsigned long free_vmemmap_pages_size_per_hpage(struct hstate *h)
@@ -269,3 +266,28 @@ void free_huge_page_vmemmap(struct hstate *h, struct page *head)
*/
vmemmap_remap_free(vmemmap_addr, vmemmap_end, vmemmap_reuse);
}
+
+void __init hugetlb_vmemmap_init(struct hstate *h)
+{
+ unsigned int nr_pages = pages_per_huge_page(h);
+ unsigned int vmemmap_pages;
+
+ if (!hugetlb_free_vmemmap_enabled)
+ return;
+
+ vmemmap_pages = (nr_pages * sizeof(struct page)) >> PAGE_SHIFT;
+ /*
+ * The head page and the first tail page are not to be freed to buddy
+ * allocator, the other pages will map to the first tail page, so they
+ * can be freed.
+ *
+ * Could RESERVE_VMEMMAP_NR be greater than @vmemmap_pages? It is true
+ * on some architectures (e.g. aarch64). See Documentation/arm64/
+ * hugetlbpage.rst for more details.
+ */
+ if (likely(vmemmap_pages > RESERVE_VMEMMAP_NR))
+ h->nr_free_vmemmap_pages = vmemmap_pages - RESERVE_VMEMMAP_NR;
+
+ pr_info("can free %d vmemmap pages for %s\n", h->nr_free_vmemmap_pages,
+ h->name);
+}
diff --git a/mm/hugetlb_vmemmap.h b/mm/hugetlb_vmemmap.h
index 6f89a9eed02c..02a21604ef1d 100644
--- a/mm/hugetlb_vmemmap.h
+++ b/mm/hugetlb_vmemmap.h
@@ -14,6 +14,7 @@
int alloc_huge_page_vmemmap(struct hstate *h, struct page *head,
gfp_t gfp_mask);
void free_huge_page_vmemmap(struct hstate *h, struct page *head);
+void hugetlb_vmemmap_init(struct hstate *h);
#else
static inline int alloc_huge_page_vmemmap(struct hstate *h, struct page *head,
gfp_t gfp_mask)
@@ -24,5 +25,9 @@ static inline int alloc_huge_page_vmemmap(struct hstate *h, struct page *head,
static inline void free_huge_page_vmemmap(struct hstate *h, struct page *head)
{
}
+
+static inline void hugetlb_vmemmap_init(struct hstate *h)
+{
+}
#endif /* CONFIG_HUGETLB_PAGE_FREE_VMEMMAP */
#endif /* _LINUX_HUGETLB_VMEMMAP_H */
--
2.11.0
