[PATCH 1/2] memory tier: Introduce sysfs for tier interleave weights.

[Ravi Jonnalagadda <ravis.opensrc@micron.com>]

From: Srinivasulu Thanneeru <sthanneeru@micron.com>

Allocating pages across tiers is accomplished by provisioning
interleave weights for each tier, with the distribution based on
these weight values.
By default, all tiers will have a weight of 1, which means
default standard page allocation. By default all nodes within
tier will have weight of 1.

Signed-off-by: Srinivasulu Thanneeru <sthanneeru@micron.com>
Co-authored-by: Ravi Jonnalagadda <ravis.opensrc@micron.com>
---
 include/linux/memory-tiers.h |  2 ++
 mm/memory-tiers.c            | 46 +++++++++++++++++++++++++++++++++++-
 2 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
index 437441cdf78f..c62d286749d0 100644
--- a/include/linux/memory-tiers.h
+++ b/include/linux/memory-tiers.h
@@ -19,6 +19,8 @@
  */
 #define MEMTIER_ADISTANCE_DRAM	((4 * MEMTIER_CHUNK_SIZE) + (MEMTIER_CHUNK_SIZE >> 1))
 
+#define MAX_TIER_INTERLEAVE_WEIGHT 100
+
 struct memory_tier;
 struct memory_dev_type {
 	/* list of memory types that are part of same tier as this type */
diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
index 37a4f59d9585..7e06c9e0fa41 100644
--- a/mm/memory-tiers.c
+++ b/mm/memory-tiers.c
@@ -13,6 +13,11 @@ struct memory_tier {
 	struct list_head list;
 	/* list of all memory types part of this tier */
 	struct list_head memory_types;
+	/*
+	 * By default all tiers will have weight as 1, which means they
+	 * follow default standard allocation.
+	 */
+	unsigned short interleave_weight;
 	/*
 	 * start value of abstract distance. memory tier maps
 	 * an abstract distance  range,
@@ -145,8 +150,45 @@ static ssize_t nodelist_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(nodelist);
 
+static ssize_t interleave_weight_show(struct device *dev,
+				      struct device_attribute *attr, char *buf)
+{
+	int ret;
+	struct memory_tier *tier = to_memory_tier(dev);
+
+	mutex_lock(&memory_tier_lock);
+	ret = sysfs_emit(buf, "%u\n", tier->interleave_weight);
+	mutex_unlock(&memory_tier_lock);
+
+	return ret;
+}
+
+static ssize_t interleave_weight_store(struct device *dev,
+				       struct device_attribute *attr,
+				       const char *buf, size_t size)
+{
+	unsigned short value;
+	int ret;
+	struct memory_tier *tier = to_memory_tier(dev);
+
+	ret = kstrtou16(buf, 0, &value);
+
+	if (ret)
+		return ret;
+	if (value > MAX_TIER_INTERLEAVE_WEIGHT)
+		return -EINVAL;
+
+	mutex_lock(&memory_tier_lock);
+	tier->interleave_weight = value;
+	mutex_unlock(&memory_tier_lock);
+
+	return size;
+}
+static DEVICE_ATTR_RW(interleave_weight);
+
 static struct attribute *memtier_dev_attrs[] = {
 	&dev_attr_nodelist.attr,
+	&dev_attr_interleave_weight.attr,
 	NULL
 };
 
@@ -489,8 +531,10 @@ static struct memory_tier *set_node_memory_tier(int node)
 	memtype = node_memory_types[node].memtype;
 	node_set(node, memtype->nodes);
 	memtier = find_create_memory_tier(memtype);
-	if (!IS_ERR(memtier))
+	if (!IS_ERR(memtier)) {
 		rcu_assign_pointer(pgdat->memtier, memtier);
+		memtier->interleave_weight = 1;
+	}
 	return memtier;
 }
 
-- 
2.39.3