[PATCH v6 09/13] mm/demotion: Add pg_data_t member to track node memory tier details

Aneesh Kumar K.V
2022-06-10T13:55:42Z

Also update different helpes to use NODE_DATA()->memtier. Since
node specific memtier can change based on the reassignment of
NUMA node to a different memory tiers, accessing NODE_DATA()->memtier
needs to under an rcu read lock of memory_tier_lock.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
---
include/linux/memory-tiers.h | 14 +++++
include/linux/mmzone.h | 3 ++
mm/memory-tiers.c | 102 ++++++++++++++++++++++++++---------
3 files changed, 94 insertions(+), 25 deletions(-)

diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
index 52896f5970b7..53f3e4c7cba8 100644
--- a/include/linux/memory-tiers.h
+++ b/include/linux/memory-tiers.h
@@ -6,6 +6,9 @@

#ifdef CONFIG_TIERED_MEMORY

+#include <linux/device.h>
+#include <linux/nodemask.h>
+
#define MEMORY_TIER_HBM_GPU 0
#define MEMORY_TIER_DRAM 1
#define MEMORY_TIER_PMEM 2
@@ -18,13 +21,24 @@
#define MAX_STATIC_MEMORY_TIERS 3
#define MAX_MEMORY_TIERS (MAX_STATIC_MEMORY_TIERS + 2)

+struct memory_tier {
+ struct list_head list;
+ struct device dev;
+ nodemask_t nodelist;
+ int rank;
+};
+
extern bool numa_demotion_enabled;
int node_create_and_set_memory_tier(int node, int tier);
int next_demotion_node(int node);
int node_set_memory_tier(int node, int tier);
int node_get_memory_tier_id(int node);
int node_reset_memory_tier(int node, int tier);
+struct memory_tier *node_get_memory_tier(int node);
+void node_put_memory_tier(struct memory_tier *memtier);
+
#else
+
#define numa_demotion_enabled false
static inline int next_demotion_node(int node)
{
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index aab70355d64f..c4fcfd2b9980 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -928,6 +928,9 @@ typedef struct pglist_data {
/* Per-node vmstats */
struct per_cpu_nodestat __percpu *per_cpu_nodestats;
atomic_long_t vm_stat[NR_VM_NODE_STAT_ITEMS];
+#ifdef CONFIG_TIERED_MEMORY
+ struct memory_tier *memtier;
+#endif
} pg_data_t;

#define node_present_pages(nid) (NODE_DATA(nid)->node_present_pages)
diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
index de3b7403ae6f..429aa864edb0 100644
--- a/mm/memory-tiers.c
+++ b/mm/memory-tiers.c
@@ -1,22 +1,14 @@
// SPDX-License-Identifier: GPL-2.0
#include <linux/types.h>
-#include <linux/device.h>
-#include <linux/nodemask.h>
#include <linux/slab.h>
#include <linux/memory-tiers.h>
#include <linux/random.h>
#include <linux/memory.h>
#include <linux/idr.h>
+#include <linux/rcupdate.h>

#include "internal.h"

-struct memory_tier {
- struct list_head list;
- struct device dev;
- nodemask_t nodelist;
- int rank;
-};
-
struct demotion_nodes {
nodemask_t preferred;
};
@@ -212,13 +204,17 @@ static void unregister_memory_tier(struct memory_tier *memtier)

static struct memory_tier *__node_get_memory_tier(int node)
{
- struct memory_tier *memtier;
+ pg_data_t *pgdat;

- list_for_each_entry(memtier, &memory_tiers, list) {
- if (node_isset(node, memtier->nodelist))
- return memtier;
- }
- return NULL;
+ pgdat = NODE_DATA(node);
+ if (!pgdat)
+ return NULL;
+ /*
+ * Since we hold memory_tier_lock, we can avoid
+ * RCU read locks when accessing the details. No
+ * parallel updates are possible here.
+ */
+ return pgdat->memtier;
}

static struct memory_tier *__get_memory_tier_from_id(int id)
@@ -232,6 +228,32 @@ static struct memory_tier *__get_memory_tier_from_id(int id)
return NULL;
}

+/*
+ * Called with memory_tier_lock. Hence the device references cannot
+ * be dropped during this function.
+ */
+static void memtier_node_set(int node, struct memory_tier *memtier)
+{
+ pg_data_t *pgdat;
+ struct memory_tier *current_memtier;
+
+ pgdat = NODE_DATA(node);
+ if (!pgdat)
+ return;
+ /*
+ * Make sure we mark the memtier NULL before we assign the new memory tier
+ * to the NUMA node. This make sure that anybody looking at NODE_DATA
+ * finds a NULL memtier or the one which is still valid.
+ */
+ current_memtier = rcu_dereference(pgdat->memtier);
+ rcu_assign_pointer(pgdat->memtier, NULL);
+ if (current_memtier)
+ node_clear(node, current_memtier->nodelist);
+ synchronize_rcu();
+ node_set(node, memtier->nodelist);
+ rcu_assign_pointer(pgdat->memtier, memtier);
+}
+
static int __node_create_and_set_memory_tier(int node, int tier)
{
int ret = 0;
@@ -252,7 +274,7 @@ static int __node_create_and_set_memory_tier(int node, int tier)
goto out;
}
}
- node_set(node, memtier->nodelist);
+ memtier_node_set(node, memtier);
out:
return ret;
}
@@ -274,12 +296,10 @@ int node_create_and_set_memory_tier(int node, int tier)
if (current_tier->dev.id == tier)
goto out;

- node_clear(node, current_tier->nodelist);
-
ret = __node_create_and_set_memory_tier(node, tier);
if (ret) {
/* reset it back to older tier */
- node_set(node, current_tier->nodelist);
+ memtier_node_set(node, current_tier);
goto out;
}

@@ -304,7 +324,7 @@ static int __node_set_memory_tier(int node, int tier)
ret = -EINVAL;
goto out;
}
- node_set(node, memtier->nodelist);
+ memtier_node_set(node, memtier);
out:
return ret;
}
@@ -360,12 +380,10 @@ int node_reset_memory_tier(int node, int tier)
if (!current_tier || current_tier->dev.id == tier)
goto out;

- node_clear(node, current_tier->nodelist);
-
ret = __node_set_memory_tier(node, tier);
if (ret) {
/* reset it back to older tier */
- node_set(node, current_tier->nodelist);
+ memtier_node_set(node, current_tier);
goto out;
}

@@ -379,6 +397,34 @@ int node_reset_memory_tier(int node, int tier)
return ret;
}

+/*
+ * lockless access to memory tier of a NUMA node.
+ */
+struct memory_tier *node_get_memory_tier(int node)
+{
+ pg_data_t *pgdat;
+ struct memory_tier *memtier;
+
+ pgdat = NODE_DATA(node);
+ if (!pgdat)
+ return NULL;
+
+ rcu_read_lock();
+ memtier = rcu_dereference(pgdat->memtier);
+ if (!memtier)
+ goto out;
+
+ get_device(&memtier->dev);
+out:
+ rcu_read_unlock();
+ return memtier;
+}
+
+void node_put_memory_tier(struct memory_tier *memtier)
+{
+ put_device(&memtier->dev);
+}
+
/**
* next_demotion_node() - Get the next node in the demotion path
* @node: The starting node to lookup the next node
@@ -641,7 +687,7 @@ static const struct attribute_group *memory_tier_attr_groups[] = {

static int __init memory_tier_init(void)
{
- int ret;
+ int ret, node;
struct memory_tier *memtier;

ret = subsys_system_register(&memory_tier_subsys, memory_tier_attr_groups);
@@ -660,7 +706,13 @@ static int __init memory_tier_init(void)
__func__, PTR_ERR(memtier));

/* CPU only nodes are not part of memory tiers. */
- memtier->nodelist = node_states[N_MEMORY];
+ for_each_node_state(node, N_MEMORY) {
+ /*
+ * Should be safe to do this early in the boot.
+ */
+ NODE_DATA(node)->memtier = memtier;
+ node_set(node, memtier->nodelist);
+ }
migrate_on_reclaim_init();

return 0;
--
2.36.1