[PATCH v3 updated] mm/demotion: Expose memory tier details via sysfs

Aneesh Kumar K.V
2022-08-30T08:18:22Z

This patch adds /sys/devices/virtual/memory_tiering/ where all memory tier
related details can be found. All allocated memory tiers will be listed
there as /sys/devices/virtual/memory_tiering/memory_tierN/

The nodes which are part of a specific memory tier can be listed via
/sys/devices/virtual/memory_tiering/memory_tierN/nodes

A directory hierarchy looks like
:/sys/devices/virtual/memory_tiering$ tree memory_tier4/
memory_tier4/
├── nodes
├── subsystem -> ../../../../bus/memory_tiering
└── uevent

All toptier nodes are listed via
/sys/devices/virtual/memory_tiering/toptier_nodes

:/sys/devices/virtual/memory_tiering$ cat toptier_nodes
0,2
:/sys/devices/virtual/memory_tiering$ cat memory_tier4/nodes
0,2

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
---

Changes from v2:
* update macro to static inline
* Fix build error with CONFIG_MIGRATION disabled
* drop abstract_distance
* update commit message

.../ABI/testing/sysfs-kernel-mm-memory-tiers | 35 ++++
mm/memory-tiers.c | 154 +++++++++++++++---
2 files changed, 167 insertions(+), 22 deletions(-)
create mode 100644 Documentation/ABI/testing/sysfs-kernel-mm-memory-tiers

diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-memory-tiers b/Documentation/ABI/testing/sysfs-kernel-mm-memory-tiers
new file mode 100644
index 000000000000..55051fcf5502
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-kernel-mm-memory-tiers
@@ -0,0 +1,35 @@
+What: /sys/devices/virtual/memory_tiering/
+Date: August 2022
+Contact: Linux memory management mailing list <linux-mm@kvack.org>
+Description: A collection of all the memory tiers allocated.
+
+ Individual memory tier details are contained in subdirectories
+ named by the abstract distance of the memory tier.
+
+ /sys/devices/virtual/memory_tiering/memory_tierN/
+
+
+What: /sys/devices/virtual/memory_tiering/memory_tierN/
+ /sys/devices/virtual/memory_tiering/memory_tierN/nodes
+Date: August 2022
+Contact: Linux memory management mailing list <linux-mm@kvack.org>
+Description: Directory with details of a specific memory tier
+
+ This is the directory containing information about a particular
+ memory tier, memtierN, where N is derived based on abstract distance.
+
+ A smaller value of N implies a higher (faster) memory tier in the
+ hierarchy.
+
+ nodes: NUMA nodes that are part of this memory tier.
+
+
+What: /sys/devices/virtual/memory_tiering/toptier_nodes
+Date: August 2022
+Contact: Linux memory management mailing list <linux-mm@kvack.org>
+Description: Toptier node mask
+
+ A toptier is defined as the memory tier from which memory promotion
+ is not done by the kernel.
+
+ toptier_nodes: Union of NUMA nodes that are part of each toptier.
diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
index c82eb0111383..33673ed9b3dc 100644
--- a/mm/memory-tiers.c
+++ b/mm/memory-tiers.c
@@ -19,6 +19,7 @@ struct memory_tier {
* adistance_start .. adistance_start + MEMTIER_CHUNK_SIZE
*/
int adistance_start;
+ struct device dev;
/* All the nodes that are part of all the lower memory tiers. */
nodemask_t lower_tier_mask;
};
@@ -36,6 +37,12 @@ static DEFINE_MUTEX(memory_tier_lock);
static LIST_HEAD(memory_tiers);
static struct node_memory_type_map node_memory_types[MAX_NUMNODES];
static struct memory_dev_type *default_dram_type;
+
+static struct bus_type memory_tier_subsys = {
+ .name = "memory_tiering",
+ .dev_name = "memory_tier",
+};
+
#ifdef CONFIG_MIGRATION
static int top_tier_adistance;
/*
@@ -98,8 +105,63 @@ static int top_tier_adistance;
static struct demotion_nodes *node_demotion __read_mostly;
#endif /* CONFIG_MIGRATION */

+static inline struct memory_tier *to_memory_tier(struct device *device)
+{
+ return container_of(device, struct memory_tier, dev);
+}
+
+static __always_inline nodemask_t get_memtier_nodemask(struct memory_tier *memtier)
+{
+ nodemask_t nodes = NODE_MASK_NONE;
+ struct memory_dev_type *memtype;
+
+ list_for_each_entry(memtype, &memtier->memory_types, tier_sibiling)
+ nodes_or(nodes, nodes, memtype->nodes);
+
+ return nodes;
+}
+
+static void memory_tier_device_release(struct device *dev)
+{
+ struct memory_tier *tier = to_memory_tier(dev);
+ /*
+ * synchronize_rcu in clear_node_memory_tier makes sure
+ * we don't have rcu access to this memory tier.
+ */
+ kfree(tier);
+}
+
+static ssize_t nodes_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ int ret;
+ nodemask_t nmask;
+
+ mutex_lock(&memory_tier_lock);
+ nmask = get_memtier_nodemask(to_memory_tier(dev));
+ ret = sysfs_emit(buf, "%*pbl\n", nodemask_pr_args(&nmask));
+ mutex_unlock(&memory_tier_lock);
+ return ret;
+}
+static DEVICE_ATTR_RO(nodes);
+
+static struct attribute *memtier_dev_attrs[] = {
+ &dev_attr_nodes.attr,
+ NULL
+};
+
+static const struct attribute_group memtier_dev_group = {
+ .attrs = memtier_dev_attrs,
+};
+
+static const struct attribute_group *memtier_dev_groups[] = {
+ &memtier_dev_group,
+ NULL
+};
+
static struct memory_tier *find_create_memory_tier(struct memory_dev_type *memtype)
{
+ int ret;
bool found_slot = false;
struct memory_tier *memtier, *new_memtier;
int adistance = memtype->adistance;
@@ -123,15 +185,14 @@ static struct memory_tier *find_create_memory_tier(struct memory_dev_type *memty

list_for_each_entry(memtier, &memory_tiers, list) {
if (adistance == memtier->adistance_start) {
- list_add(&memtype->tier_sibiling, &memtier->memory_types);
- return memtier;
+ goto link_memtype;
} else if (adistance < memtier->adistance_start) {
found_slot = true;
break;
}
}

- new_memtier = kmalloc(sizeof(struct memory_tier), GFP_KERNEL);
+ new_memtier = kzalloc(sizeof(struct memory_tier), GFP_KERNEL);
if (!new_memtier)
return ERR_PTR(-ENOMEM);

@@ -142,8 +203,23 @@ static struct memory_tier *find_create_memory_tier(struct memory_dev_type *memty
list_add_tail(&new_memtier->list, &memtier->list);
else
list_add_tail(&new_memtier->list, &memory_tiers);
- list_add(&memtype->tier_sibiling, &new_memtier->memory_types);
- return new_memtier;
+
+ new_memtier->dev.id = adistance >> MEMTIER_CHUNK_BITS;
+ new_memtier->dev.bus = &memory_tier_subsys;
+ new_memtier->dev.release = memory_tier_device_release;
+ new_memtier->dev.groups = memtier_dev_groups;
+
+ ret = device_register(&new_memtier->dev);
+ if (ret) {
+ list_del(&memtier->list);
+ put_device(&memtier->dev);
+ return ERR_PTR(ret);
+ }
+ memtier = new_memtier;
+
+link_memtype:
+ list_add(&memtype->tier_sibiling, &memtier->memory_types);
+ return memtier;
}

static struct memory_tier *__node_get_memory_tier(int node)
@@ -275,17 +351,6 @@ static void disable_all_demotion_targets(void)
synchronize_rcu();
}

-static __always_inline nodemask_t get_memtier_nodemask(struct memory_tier *memtier)
-{
- nodemask_t nodes = NODE_MASK_NONE;
- struct memory_dev_type *memtype;
-
- list_for_each_entry(memtype, &memtier->memory_types, tier_sibiling)
- nodes_or(nodes, nodes, memtype->nodes);
-
- return nodes;
-}
-
/*
* Find an automatic demotion target for all memory
* nodes. Failing here is OK. It might just indicate
@@ -433,11 +498,7 @@ static struct memory_tier *set_node_memory_tier(int node)
static void destroy_memory_tier(struct memory_tier *memtier)
{
list_del(&memtier->list);
- /*
- * synchronize_rcu in clear_node_memory_tier makes sure
- * we don't have rcu access to this memory tier.
- */
- kfree(memtier);
+ device_unregister(&memtier->dev);
}

static bool clear_node_memory_tier(int node)
@@ -564,11 +625,60 @@ static int __meminit memtier_hotplug_callback(struct notifier_block *self,
return notifier_from_errno(0);
}

+#ifdef CONFIG_MIGRATION
+static ssize_t toptier_nodes_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ int ret;
+ nodemask_t nmask, top_tier_mask = NODE_MASK_NONE;
+ struct memory_tier *memtier = to_memory_tier(dev);
+
+ mutex_lock(&memory_tier_lock);
+ list_for_each_entry(memtier, &memory_tiers, list) {
+ if (memtier->adistance_start > top_tier_adistance)
+ break;
+ nmask = get_memtier_nodemask(memtier);
+ nodes_or(top_tier_mask, top_tier_mask, nmask);
+ }
+
+ ret = sysfs_emit(buf, "%*pbl\n", nodemask_pr_args(&top_tier_mask));
+ mutex_unlock(&memory_tier_lock);
+ return ret;
+}
+#else
+static ssize_t toptier_nodes_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ nodemask_t top_tier_mask = node_states[N_MEMORY];
+
+ return sysfs_emit(buf, "%*pbl\n", nodemask_pr_args(&top_tier_mask));
+}
+#endif
+static DEVICE_ATTR_RO(toptier_nodes);
+
+static struct attribute *memtier_subsys_attrs[] = {
+ &dev_attr_toptier_nodes.attr,
+ NULL
+};
+
+static const struct attribute_group memtier_subsys_group = {
+ .attrs = memtier_subsys_attrs,
+};
+
+static const struct attribute_group *memtier_subsys_groups[] = {
+ &memtier_subsys_group,
+ NULL
+};
+
static int __init memory_tier_init(void)
{
- int node;
+ int ret, node;
struct memory_tier *memtier;

+ ret = subsys_virtual_register(&memory_tier_subsys, memtier_subsys_groups);
+ if (ret)
+ panic("%s() failed to register memory tier subsystem\n", __func__);
+
#ifdef CONFIG_MIGRATION
node_demotion = kcalloc(nr_node_ids, sizeof(struct demotion_nodes),
GFP_KERNEL);
--
2.37.2