[PATCH 2/7] x86, mm: Use big page size for small memory range

[Yinghai Lu]

We could map small range in the middle of big range at first, so should use
big page size at first to avoid using small page size to break down page table.

Only can set big page bit when that range has big ram area around it.

Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>
---
 arch/x86/mm/init.c |   32 ++++++++++++++++++++++++++++++++
 1 files changed, 32 insertions(+), 0 deletions(-)

diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index c12dfd5..ebf76ce 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -88,6 +88,35 @@ static int __meminit save_mr(struct map_range *mr, int nr_range,
 	return nr_range;
 }
 
+/*
+ * adjust the page_size_mask for small range to go with
+ *	big page size instead small one if nearby are ram too.
+ */
+static void __init_refok adjust_range_page_size_mask(struct map_range *mr,
+							 int nr_range)
+{
+	int i;
+
+	for (i = 0; i < nr_range; i++) {
+		if ((page_size_mask & (1<<PG_LEVEL_2M)) &&
+		    !(mr[i].page_size_mask & (1<<PG_LEVEL_2M))) {
+			unsigned long start = round_down(mr[i].start, PMD_SIZE);
+			unsigned long end = round_up(mr[i].end, PMD_SIZE);
+
+			if (memblock_is_region_memory(start, end - start))
+				mr[i].page_size_mask |= 1<<PG_LEVEL_2M;
+		}
+		if ((page_size_mask & (1<<PG_LEVEL_1G)) &&
+		    !(mr[i].page_size_mask & (1<<PG_LEVEL_1G))) {
+			unsigned long start = round_down(mr[i].start, PUD_SIZE);
+			unsigned long end = round_up(mr[i].end, PUD_SIZE);
+
+			if (memblock_is_region_memory(start, end - start))
+				mr[i].page_size_mask |= 1<<PG_LEVEL_1G;
+		}
+	}
+}
+
 static int __meminit split_mem_range(struct map_range *mr, int nr_range,
 				     unsigned long start,
 				     unsigned long end)
@@ -182,6 +211,9 @@ static int __meminit split_mem_range(struct map_range *mr, int nr_range,
 		nr_range--;
 	}
 
+	if (!after_bootmem)
+		adjust_range_page_size_mask(mr, nr_range);
+
 	for (i = 0; i < nr_range; i++)
 		printk(KERN_DEBUG " [mem %#010lx-%#010lx] page %s\n",
 				mr[i].start, mr[i].end - 1,
-- 
1.7.7

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