1 files changed, 61 insertions, 6 deletions

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index fa7948042bff..58ae2f746b3e 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -829,17 +829,42 @@ void __init paging_init(void)
 #ifdef CONFIG_SPARSEMEM_VMEMMAP
 #define PAGE_UNUSED 0xFD
 
+/*
+ * The unused vmemmap range, which was not yet memset(PAGE_UNUSED), ranges
+ * from unused_pmd_start to next PMD_SIZE boundary.
+ */
+static unsigned long unused_pmd_start __meminitdata;
+
+static void __meminit vmemmap_flush_unused_pmd(void)
+{
+	if (!unused_pmd_start)
+		return;
+	/*
+	 * Clears (unused_pmd_start, PMD_END]
+	 */
+	memset((void *)unused_pmd_start, PAGE_UNUSED,
+	       ALIGN(unused_pmd_start, PMD_SIZE) - unused_pmd_start);
+	unused_pmd_start = 0;
+}
+
+#ifdef CONFIG_MEMORY_HOTPLUG
 /* Returns true if the PMD is completely unused and thus it can be freed */
 static bool __meminit vmemmap_pmd_is_unused(unsigned long addr, unsigned long end)
 {
 	unsigned long start = ALIGN_DOWN(addr, PMD_SIZE);
 
+	/*
+	 * Flush the unused range cache to ensure that memchr_inv() will work
+	 * for the whole range.
+	 */
+	vmemmap_flush_unused_pmd();
 	memset((void *)addr, PAGE_UNUSED, end - addr);
 
 	return !memchr_inv((void *)start, PAGE_UNUSED, PMD_SIZE);
 }
+#endif
 
-static void __meminit vmemmap_use_sub_pmd(unsigned long start)
+static void __meminit __vmemmap_use_sub_pmd(unsigned long start)
 {
 	/*
 	 * As we expect to add in the same granularity as we remove, it's
@@ -851,23 +876,53 @@ static void __meminit vmemmap_use_sub_pmd(unsigned long start)
 	memset((void *)start, 0, sizeof(struct page));
 }
 
+static void __meminit vmemmap_use_sub_pmd(unsigned long start, unsigned long end)
+{
+	/*
+	 * We only optimize if the new used range directly follows the
+	 * previously unused range (esp., when populating consecutive sections).
+	 */
+	if (unused_pmd_start == start) {
+		if (likely(IS_ALIGNED(end, PMD_SIZE)))
+			unused_pmd_start = 0;
+		else
+			unused_pmd_start = end;
+		return;
+	}
+
+	/*
+	 * If the range does not contiguously follows previous one, make sure
+	 * to mark the unused range of the previous one so it can be removed.
+	 */
+	vmemmap_flush_unused_pmd();
+	__vmemmap_use_sub_pmd(start);
+}
+
+
 static void __meminit vmemmap_use_new_sub_pmd(unsigned long start, unsigned long end)
 {
+	vmemmap_flush_unused_pmd();
+
 	/*
 	 * Could be our memmap page is filled with PAGE_UNUSED already from a
 	 * previous remove. Make sure to reset it.
 	 */
-	vmemmap_use_sub_pmd(start);
+	__vmemmap_use_sub_pmd(start);
 
 	/*
 	 * Mark with PAGE_UNUSED the unused parts of the new memmap range
 	 */
 	if (!IS_ALIGNED(start, PMD_SIZE))
 		memset((void *)start, PAGE_UNUSED,
-		        start - ALIGN_DOWN(start, PMD_SIZE));
+			start - ALIGN_DOWN(start, PMD_SIZE));
+
+	/*
+	 * We want to avoid memset(PAGE_UNUSED) when populating the vmemmap of
+	 * consecutive sections. Remember for the last added PMD where the
+	 * unused range begins.
+	 */
 	if (!IS_ALIGNED(end, PMD_SIZE))
-		memset((void *)end, PAGE_UNUSED,
-		        ALIGN(end, PMD_SIZE) - end);
+		unused_pmd_start = end;
 }
 #endif
 
@@ -1538,7 +1593,7 @@ static int __meminit vmemmap_populate_hugepages(unsigned long start,
 				return -ENOMEM; /* no fallback */
 		} else if (pmd_large(*pmd)) {
 			vmemmap_verify((pte_t *)pmd, node, addr, next);
-			vmemmap_use_sub_pmd(addr);
+			vmemmap_use_sub_pmd(addr, next);
 			continue;
 		}
 		if (vmemmap_populate_basepages(addr, next, node, NULL))