[PATCH v6 08/13] mm/demotion: Add support for memory tier creation from userspace

Aneesh Kumar K.V
2022-06-10T13:56:22Z

This patch adds support to create memory tiers with specific rank
value from userspace. To avoid race while creating memory tiers
/sys/devices/system/memtier/create_tier_from_rank file is provided.
Writing to this file with a specific rank value creates a new memory
tier with the specified rank value.

Memory tiers created from userspace gets destroyed when the memory
tier nodelist becomes empty.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
---
include/linux/memory-tiers.h | 3 +-
mm/memory-tiers.c | 74 ++++++++++++++++++++++++++++++++++++
2 files changed, 76 insertions(+), 1 deletion(-)

diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
index e70f0040d845..52896f5970b7 100644
--- a/include/linux/memory-tiers.h
+++ b/include/linux/memory-tiers.h
@@ -15,7 +15,8 @@
#define MEMORY_RANK_PMEM 100

#define DEFAULT_MEMORY_TIER MEMORY_TIER_DRAM
-#define MAX_MEMORY_TIERS 3
+#define MAX_STATIC_MEMORY_TIERS 3
+#define MAX_MEMORY_TIERS (MAX_STATIC_MEMORY_TIERS + 2)

extern bool numa_demotion_enabled;
int node_create_and_set_memory_tier(int node, int tier);
diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
index 7bfdfac4d43e..de3b7403ae6f 100644
--- a/mm/memory-tiers.c
+++ b/mm/memory-tiers.c
@@ -6,6 +6,7 @@
#include <linux/memory-tiers.h>
#include <linux/random.h>
#include <linux/memory.h>
+#include <linux/idr.h>

#include "internal.h"

@@ -126,9 +127,12 @@ static const struct attribute_group *memory_tier_dev_groups[] = {
NULL
};

+static DEFINE_IDA(memtier_dev_id);
static void memory_tier_device_release(struct device *dev)
{
struct memory_tier *tier = to_memory_tier(dev);
+ if (tier->dev.id >= MAX_STATIC_MEMORY_TIERS)
+ ida_free(&memtier_dev_id, tier->dev.id);

kfree(tier);
}
@@ -195,6 +199,17 @@ static struct memory_tier *register_memory_tier(unsigned int tier,
return memtier;
}

+static void unregister_memory_tier(struct memory_tier *memtier)
+{
+ /*
+ * Don't destroy static memory tiers.
+ */
+ if (memtier->dev.id < MAX_STATIC_MEMORY_TIERS)
+ return;
+ list_del(&memtier->list);
+ device_unregister(&memtier->dev);
+}
+
static struct memory_tier *__node_get_memory_tier(int node)
{
struct memory_tier *memtier;
@@ -267,6 +282,10 @@ int node_create_and_set_memory_tier(int node, int tier)
node_set(node, current_tier->nodelist);
goto out;
}
+
+ if (nodes_empty(current_tier->nodelist))
+ unregister_memory_tier(current_tier);
+
establish_migration_targets();
out:
mutex_unlock(&memory_tier_lock);
@@ -350,6 +369,9 @@ int node_reset_memory_tier(int node, int tier)
goto out;
}

+ if (nodes_empty(current_tier->nodelist))
+ unregister_memory_tier(current_tier);
+
establish_migration_targets();
out:
mutex_unlock(&memory_tier_lock);
@@ -550,9 +572,61 @@ default_tier_show(struct device *dev, struct device_attribute *attr, char *buf)
}
static DEVICE_ATTR_RO(default_tier);

+static inline int memtier_alloc_id(void)
+{
+ return ida_alloc_range(&memtier_dev_id,
+ MAX_STATIC_MEMORY_TIERS,
+ MAX_MEMORY_TIERS - 1, GFP_KERNEL);
+}
+
+static ssize_t create_tier_from_rank_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ int ret, tier, rank;
+ struct memory_tier *memtier;
+
+ ret = kstrtouint(buf, 10, &rank);
+ if (ret)
+ return ret;
+
+ if (rank == MEMORY_RANK_HBM_GPU ||
+ rank == MEMORY_RANK_DRAM ||
+ rank == MEMORY_RANK_PMEM)
+ return -EINVAL;
+
+ mutex_lock(&memory_tier_lock);
+ /*
+ * We don't support multiple tiers with same rank value
+ */
+ list_for_each_entry(memtier, &memory_tiers, list) {
+ if (memtier->rank == rank) {
+ ret = -EINVAL;
+ goto out;
+ }
+ }
+ tier = memtier_alloc_id();
+ if (tier < 0) {
+ ret = -ENOSPC;
+ goto out;
+ }
+ memtier = register_memory_tier(tier, rank);
+ if (IS_ERR(memtier)) {
+ ret = PTR_ERR(memtier);
+ goto out;
+ }
+
+ ret = count;
+out:
+ mutex_unlock(&memory_tier_lock);
+ return ret;
+}
+static DEVICE_ATTR_WO(create_tier_from_rank);
+
static struct attribute *memory_tier_attrs[] = {
&dev_attr_max_tier.attr,
&dev_attr_default_tier.attr,
+ &dev_attr_create_tier_from_rank.attr,
NULL
};

--
2.36.1