[PATCH v9 8/8] mm/demotion: Update node_is_toptier to work with memory tiers

[Aneesh Kumar K.V]

With memory tiers support we can have memory only NUMA nodes
in the top tier from which we want to avoid promotion tracking NUMA
faults. Update node_is_toptier to work with memory tiers.
All NUMA nodes are by default top tier nodes. With lower memory
tiers added we consider all memory tiers above a memory tier having
CPU NUMA nodes as a top memory tier

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
---
 include/linux/memory-tiers.h |  6 ++++++
 include/linux/node.h         |  5 -----
 mm/huge_memory.c             |  1 +
 mm/memory-tiers.c            | 41 ++++++++++++++++++++++++++++++++++++
 mm/migrate.c                 |  1 +
 mm/mprotect.c                |  1 +
 6 files changed, 50 insertions(+), 5 deletions(-)

diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
index 8137e9322603..0e5591ddc74b 100644
--- a/include/linux/memory-tiers.h
+++ b/include/linux/memory-tiers.h
@@ -31,6 +31,7 @@ static inline void node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *target
 	*targets = NODE_MASK_NONE;
 }
 #endif /* CONFIG_MIGRATION */
+bool node_is_toptier(int node);
 
 #else
 
@@ -49,5 +50,10 @@ static inline void node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *target
 {
 	*targets = NODE_MASK_NONE;
 }
+
+static inline bool node_is_toptier(int node)
+{
+	return true;
+}
 #endif	/* CONFIG_NUMA */
 #endif  /* _LINUX_MEMORY_TIERS_H */
diff --git a/include/linux/node.h b/include/linux/node.h
index 40d641a8bfb0..9ec680dd607f 100644
--- a/include/linux/node.h
+++ b/include/linux/node.h
@@ -185,9 +185,4 @@ static inline void register_hugetlbfs_with_node(node_registration_func_t reg,
 
 #define to_node(device) container_of(device, struct node, dev)
 
-static inline bool node_is_toptier(int node)
-{
-	return node_state(node, N_CPU);
-}
-
 #endif /* _LINUX_NODE_H_ */
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 834f288b3769..8405662646e9 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -35,6 +35,7 @@
 #include <linux/numa.h>
 #include <linux/page_owner.h>
 #include <linux/sched/sysctl.h>
+#include <linux/memory-tiers.h>
 
 #include <asm/tlb.h>
 #include <asm/pgalloc.h>
diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
index 98e55600f250..923b056e222c 100644
--- a/mm/memory-tiers.c
+++ b/mm/memory-tiers.c
@@ -26,6 +26,7 @@ struct demotion_nodes {
 static void establish_migration_targets(void);
 static DEFINE_MUTEX(memory_tier_lock);
 static LIST_HEAD(memory_tiers);
+static int top_tier_id;
 /*
  * node_demotion[] examples:
  *
@@ -268,6 +269,31 @@ static int node_set_memory_tier(int node, int tier)
 	return ret;
 }
 
+bool node_is_toptier(int node)
+{
+	bool toptier;
+	pg_data_t *pgdat;
+	struct memory_tier *memtier;
+
+	pgdat = NODE_DATA(node);
+	if (!pgdat)
+		return false;
+
+	rcu_read_lock();
+	memtier = rcu_dereference(pgdat->memtier);
+	if (!memtier) {
+		toptier = true;
+		goto out;
+	}
+	if (memtier->id >= top_tier_id)
+		toptier = true;
+	else
+		toptier = false;
+out:
+	rcu_read_unlock();
+	return toptier;
+}
+
 #ifdef CONFIG_MIGRATION
 void node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *targets)
 {
@@ -440,6 +466,21 @@ static void establish_migration_targets(void)
 		} while (1);
 	}
 build_lower_tier_mask:
+	/*
+	 * Promotion is allowed from a memory tier to higher
+	 * memory tier only if the memory tier doesn't include
+	 * compute. We want to  skip promotion from a memory tier,
+	 * if any node that is  part of the memory tier have CPUs.
+	 * Once we detect such a memory tier, we consider that tier
+	 * as top tiper from which promotion is not allowed.
+	 */
+	list_for_each_entry_reverse(memtier, &memory_tiers, list) {
+		nodes_and(used, node_states[N_CPU], memtier->nodelist);
+		if (!nodes_empty(used)) {
+			top_tier_id = memtier->id;
+			break;
+		}
+	}
 	/*
 	 * Now build the lower_tier mask for each node collecting node mask from
 	 * all memory tier below it. This allows us to fallback demotion page
diff --git a/mm/migrate.c b/mm/migrate.c
index c758c9c21d7d..1da81136eaaa 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -50,6 +50,7 @@
 #include <linux/memory.h>
 #include <linux/random.h>
 #include <linux/sched/sysctl.h>
+#include <linux/memory-tiers.h>
 
 #include <asm/tlbflush.h>
 
diff --git a/mm/mprotect.c b/mm/mprotect.c
index ba5592655ee3..92a2fc0fa88b 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -31,6 +31,7 @@
 #include <linux/pgtable.h>
 #include <linux/sched/sysctl.h>
 #include <linux/userfaultfd_k.h>
+#include <linux/memory-tiers.h>
 #include <asm/cacheflush.h>
 #include <asm/mmu_context.h>
 #include <asm/tlbflush.h>
-- 
2.36.1