[PATCH 2/2] mm: Add sysfs interface to dump each node's zonelist information

[Anshuman Khandual]

Each individual node in the system has a ZONELIST_FALLBACK zonelist
and a ZONELIST_NOFALLBACK zonelist. These zonelists decide fallback
order of zones during memory allocations. Sometimes it helps to dump
these zonelists to see the priority order of various zones in them.
This change just adds a sysfs interface for doing the same.

Example zonelist information from a KVM guest.

[NODE (0)]
        ZONELIST_FALLBACK
        (0) (node 0) (zone DMA c00000000140c000)
        (1) (node 1) (zone DMA c000000100000000)
        (2) (node 2) (zone DMA c000000200000000)
        (3) (node 3) (zone DMA c000000300000000)
        ZONELIST_NOFALLBACK
        (0) (node 0) (zone DMA c00000000140c000)
[NODE (1)]
        ZONELIST_FALLBACK
        (0) (node 1) (zone DMA c000000100000000)
        (1) (node 2) (zone DMA c000000200000000)
        (2) (node 3) (zone DMA c000000300000000)
        (3) (node 0) (zone DMA c00000000140c000)
        ZONELIST_NOFALLBACK
        (0) (node 1) (zone DMA c000000100000000)
[NODE (2)]
        ZONELIST_FALLBACK
        (0) (node 2) (zone DMA c000000200000000)
        (1) (node 3) (zone DMA c000000300000000)
        (2) (node 0) (zone DMA c00000000140c000)
        (3) (node 1) (zone DMA c000000100000000)
        ZONELIST_NOFALLBACK
        (0) (node 2) (zone DMA c000000200000000)
[NODE (3)]
        ZONELIST_FALLBACK
        (0) (node 3) (zone DMA c000000300000000)
        (1) (node 0) (zone DMA c00000000140c000)
        (2) (node 1) (zone DMA c000000100000000)
        (3) (node 2) (zone DMA c000000200000000)
        ZONELIST_NOFALLBACK
        (0) (node 3) (zone DMA c000000300000000)

Signed-off-by: Anshuman Khandual <khandual@xxxxxxxxxxxxxxxxxx>
---
 drivers/base/memory.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index dc75de9..8c9330a 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -442,7 +442,52 @@ print_block_size(struct device *dev, struct device_attribute *attr,
 	return sprintf(buf, "%lx\n", get_memory_block_size());
 }
 
+static ssize_t dump_zonelist(char *buf, struct zonelist *zonelist)
+{
+	unsigned int i;
+	ssize_t count = 0;
+
+	for (i = 0; zonelist->_zonerefs[i].zone; i++) {
+		count += sprintf(buf + count,
+			"\t\t(%d) (node %d) (%-10s %lx)\n", i,
+			zonelist->_zonerefs[i].zone->zone_pgdat->node_id,
+			zone_names[zonelist->_zonerefs[i].zone_idx],
+			(unsigned long) zonelist->_zonerefs[i].zone);
+	}
+	return count;
+}
+
+static ssize_t dump_zonelists(char *buf)
+{
+	struct zonelist *zonelist;
+	unsigned int node;
+	ssize_t count = 0;
+
+	for_each_online_node(node) {
+		zonelist = &(NODE_DATA(node)->
+				node_zonelists[ZONELIST_FALLBACK]);
+		count += sprintf(buf + count, "[NODE (%d)]\n", node);
+		count += sprintf(buf + count, "\tZONELIST_FALLBACK\n");
+		count += dump_zonelist(buf + count, zonelist);
+
+		zonelist = &(NODE_DATA(node)->
+				node_zonelists[ZONELIST_NOFALLBACK]);
+		count += sprintf(buf + count, "\tZONELIST_NOFALLBACK\n");
+		count += dump_zonelist(buf + count, zonelist);
+	}
+	return count;
+}
+
+static ssize_t
+print_system_zone_details(struct device *dev, struct device_attribute *attr,
+		 char *buf)
+{
+	return dump_zonelists(buf);
+}
+
+
 static DEVICE_ATTR(block_size_bytes, 0444, print_block_size, NULL);
+static DEVICE_ATTR(system_zone_details, 0444, print_system_zone_details, NULL);
 
 /*
  * Memory auto online policy.
@@ -783,6 +828,7 @@ static struct attribute *memory_root_attrs[] = {
 #endif
 
 	&dev_attr_block_size_bytes.attr,
+	&dev_attr_system_zone_details.attr,
 	&dev_attr_auto_online_blocks.attr,
 	NULL
 };
-- 
1.9.3