1 files changed, 60 insertions, 0 deletions
diff --git a/mm/hugetlb_vmemmap.h b/mm/hugetlb_vmemmap.h
new file mode 100644
index 000000000..25bd0e002
--- /dev/null
+++ b/mm/hugetlb_vmemmap.h
@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * HugeTLB Vmemmap Optimization (HVO)
+ *
+ * Copyright (c) 2020, ByteDance. All rights reserved.
+ *
+ *     Author: Muchun Song <songmuchun@bytedance.com>
+ */
+#ifndef _LINUX_HUGETLB_VMEMMAP_H
+#define _LINUX_HUGETLB_VMEMMAP_H
+#include <linux/hugetlb.h>
+
+#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
+int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head);
+void hugetlb_vmemmap_optimize(const struct hstate *h, struct page *head);
+
+/*
+ * Reserve one vmemmap page, all vmemmap addresses are mapped to it. See
+ * Documentation/vm/vmemmap_dedup.rst.
+ */
+#define HUGETLB_VMEMMAP_RESERVE_SIZE	PAGE_SIZE
+
+static inline unsigned int hugetlb_vmemmap_size(const struct hstate *h)
+{
+	return pages_per_huge_page(h) * sizeof(struct page);
+}
+
+/*
+ * Return how many vmemmap size associated with a HugeTLB page that can be
+ * optimized and can be freed to the buddy allocator.
+ */
+static inline unsigned int hugetlb_vmemmap_optimizable_size(const struct hstate *h)
+{
+	int size = hugetlb_vmemmap_size(h) - HUGETLB_VMEMMAP_RESERVE_SIZE;
+
+	if (!is_power_of_2(sizeof(struct page)))
+		return 0;
+	return size > 0 ? size : 0;
+}
+#else
+static inline int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head)
+{
+	return 0;
+}
+
+static inline void hugetlb_vmemmap_optimize(const struct hstate *h, struct page *head)
+{
+}
+
+static inline unsigned int hugetlb_vmemmap_optimizable_size(const struct hstate *h)
+{
+	return 0;
+}
+#endif /* CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP */
+
+static inline bool hugetlb_vmemmap_optimizable(const struct hstate *h)
+{
+	return hugetlb_vmemmap_optimizable_size(h) != 0;
+}
+#endif /* _LINUX_HUGETLB_VMEMMAP_H */