Message-Id: <20240621044833.3953055-1-horen.chuang@linux.dev>
Date: Fri, 21 Jun 2024 04:48:30 +0000
From: "Ho-Ren (Jack) Chuang" <horen.chuang@...ux.dev>
To: "Jonathan Cameron" <Jonathan.Cameron@...wei.com>,
	"Huang, Ying" <ying.huang@...el.com>,
	"Gregory Price" <gourry.memverge@...il.com>,
	aneesh.kumar@...ux.ibm.com,
	mhocko@...e.com,
	tj@...nel.org,
	john@...alactic.com,
	"Eishan Mirakhur" <emirakhur@...ron.com>,
	"Vinicius Tavares Petrucci" <vtavarespetr@...ron.com>,
	"Ravis OpenSrc" <Ravis.OpenSrc@...ron.com>,
	"Alistair Popple" <apopple@...dia.com>,
	"Srinivasulu Thanneeru" <sthanneeru@...ron.com>,
	"SeongJae Park" <sj@...nel.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Len Brown <lenb@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Jiang <dave.jiang@...el.com>,
	Dan Williams <dan.j.williams@...el.com>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	"Ho-Ren (Jack) Chuang" <horen.chuang@...ux.dev>,
	linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Cc: "Ho-Ren (Jack) Chuang" <horenc@...edu>,
	"Ho-Ren (Jack) Chuang" <horenchuang@...edance.com>,
	"Ho-Ren (Jack) Chuang" <horenchuang@...il.com>,
	linux-cxl@...r.kernel.org,
	qemu-devel@...gnu.org
Subject: [PATCH v1] memory tier: consolidate the initialization of memory tiers

If we simply move the set_node_memory_tier() from memory_tier_init() to
late_initcall(), it will result in HMAT not registering the
mt_adistance_algorithm callback function, because set_node_memory_tier()
is not performed during the memory tiering initialization phase,
leading to a lack of correct default_dram information.

Therefore, we introduced a nodemask to pass the information of the
default DRAM nodes. The reason for not choosing to reuse
default_dram_type->nodes is that it is not clean enough. So in the end,
we use a __initdata variable, which is a variable that is released once
initialization is complete, including both CPU and memory nodes for HMAT
to iterate through.

Besides, since default_dram_type may be checked/used during the
initialization process of HMAT and drivers, it is better to keep the
allocation of default_dram_type in memory_tier_init().

Signed-off-by: Ho-Ren (Jack) Chuang <horenchuang@...edance.com>
---
Hi all,

The current memory tier initialization process is distributed across two
different functions, memory_tier_init() and memory_tier_late_init(). This
design is hard to maintain. Thus, this patch is proposed to reduce the
possible code paths by consolidating different initialization patches into one.

The earlier discussion with Jonathan and Ying is listed here:
https://lore.kernel.org/lkml/20240405150244.00004b49@Huawei.com/

If we want to put these two initializations together, they must be placed
together in the later function. Because only at that time, the HMAT information
will be ready, adist between nodes can be calculated, and memory tiering can be
established based on the adist. So we position the initialization at
memory_tier_init() to the memory_tier_late_init() call.

Moreover, it's natural to keep memory_tier initialization in drivers at
device_initcall() level.

This patchset is based on commits cf93be18fa1b and a72a30af550c:
[0/2] https://lkml.kernel.org/r/20240405000707.2670063-1-horenchuang@bytedance.com
[1/2] https://lkml.kernel.org/r/20240405000707.2670063-2-horenchuang@bytedance.com
[1/2] https://lkml.kernel.org/r/20240405000707.2670063-3-horenchuang@bytedance.com

Thanks,
Ho-Ren (Jack) Chuang

 drivers/acpi/numa/hmat.c     |  4 ++-
 include/linux/memory-tiers.h |  6 ++++
 mm/memory-tiers.c            | 70 ++++++++++++++++++------------------
 3 files changed, 44 insertions(+), 36 deletions(-)

diff --git a/drivers/acpi/numa/hmat.c b/drivers/acpi/numa/hmat.c
index 2c8ccc91ebe6..31a77a3324a8 100644
--- a/drivers/acpi/numa/hmat.c
+++ b/drivers/acpi/numa/hmat.c
@@ -939,11 +939,13 @@ static int hmat_set_default_dram_perf(void)
 	int nid, pxm;
 	struct memory_target *target;
 	struct access_coordinate *attrs;
+	nodemask_t default_dram_nodes;
 
 	if (!default_dram_type)
 		return -EIO;
 
-	for_each_node_mask(nid, default_dram_type->nodes) {
+	default_dram_nodes = mt_get_default_dram_nodemask();
+	for_each_node_mask(nid, default_dram_nodes) {
 		pxm = node_to_pxm(nid);
 		target = find_mem_target(pxm);
 		if (!target)
diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
index 0d70788558f4..1567db7bd40e 100644
--- a/include/linux/memory-tiers.h
+++ b/include/linux/memory-tiers.h
@@ -51,6 +51,7 @@ int mt_perf_to_adistance(struct access_coordinate *perf, int *adist);
 struct memory_dev_type *mt_find_alloc_memory_type(int adist,
 						  struct list_head *memory_types);
 void mt_put_memory_types(struct list_head *memory_types);
+nodemask_t mt_get_default_dram_nodemask(void);
 #ifdef CONFIG_MIGRATION
 int next_demotion_node(int node);
 void node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *targets);
@@ -149,5 +150,10 @@ static inline struct memory_dev_type *mt_find_alloc_memory_type(int adist,
 static inline void mt_put_memory_types(struct list_head *memory_types)
 {
 }
+
+static inline nodemask_t mt_get_default_dram_nodemask(void)
+{
+	return NODE_MASK_NONE;
+}
 #endif	/* CONFIG_NUMA */
 #endif  /* _LINUX_MEMORY_TIERS_H */
diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
index 6632102bd5c9..7d4b7f53dd8f 100644
--- a/mm/memory-tiers.c
+++ b/mm/memory-tiers.c
@@ -43,6 +43,7 @@ static LIST_HEAD(memory_tiers);
 static LIST_HEAD(default_memory_types);
 static struct node_memory_type_map node_memory_types[MAX_NUMNODES];
 struct memory_dev_type *default_dram_type;
+static nodemask_t default_dram_nodes __initdata = NODE_MASK_NONE;
 
 static const struct bus_type memory_tier_subsys = {
 	.name = "memory_tiering",
@@ -125,6 +126,11 @@ static inline struct memory_tier *to_memory_tier(struct device *device)
 	return container_of(device, struct memory_tier, dev);
 }
 
+nodemask_t __init mt_get_default_dram_nodemask(void)
+{
+	return default_dram_nodes;
+}
+
 static __always_inline nodemask_t get_memtier_nodemask(struct memory_tier *memtier)
 {
 	nodemask_t nodes = NODE_MASK_NONE;
@@ -671,27 +677,38 @@ EXPORT_SYMBOL_GPL(mt_put_memory_types);
 
 /*
  * This is invoked via `late_initcall()` to initialize memory tiers for
- * CPU-less memory nodes after driver initialization, which is
- * expected to provide `adistance` algorithms.
+ * memory nodes, both with and without CPUs. After the initialization of
+ * firmware and devices, adistance algorithms are expected to be provided.
  */
 static int __init memory_tier_late_init(void)
 {
 	int nid;
+	struct memory_tier *memtier;
 
 	guard(mutex)(&memory_tier_lock);
+	/*
+	 * Look at all the existing and uninitialized N_MEMORY nodes and
+	 * add them to default memory tier or to a tier if we already have
+	 * memory types assigned.
+	 */
 	for_each_node_state(nid, N_MEMORY) {
-		/*
-		 * Some device drivers may have initialized memory tiers
-		 * between `memory_tier_init()` and `memory_tier_late_init()`,
-		 * potentially bringing online memory nodes and
-		 * configuring memory tiers. Exclude them here.
-		 */
-		if (node_memory_types[nid].memtype)
-			continue;
+		if (!node_state(nid, N_CPU))
+			/*
+			 * Some device drivers may have initialized
+			 * memory tiers, potentially bringing memory nodes
+			 * online and configuring memory tiers.
+			 * Exclude them here.
+			 */
+			if (node_memory_types[nid].memtype)
+				continue;
 
-		set_node_memory_tier(nid);
+		memtier = set_node_memory_tier(nid);
+		if (IS_ERR(memtier))
+			/*
+			 * Continue with memtiers we are able to setup.
+			 */
+			break;
 	}
-
 	establish_demotion_targets();
 
 	return 0;
@@ -876,7 +893,6 @@ static int __meminit memtier_hotplug_callback(struct notifier_block *self,
 static int __init memory_tier_init(void)
 {
 	int ret, node;
-	struct memory_tier *memtier;
 
 	ret = subsys_virtual_register(&memory_tier_subsys, NULL);
 	if (ret)
@@ -887,7 +903,8 @@ static int __init memory_tier_init(void)
 				GFP_KERNEL);
 	WARN_ON(!node_demotion);
 #endif
-	mutex_lock(&memory_tier_lock);
+
+	guard(mutex)(&memory_tier_lock);
 	/*
 	 * For now we can have 4 faster memory tiers with smaller adistance
 	 * than default DRAM tier.
@@ -898,28 +915,11 @@ static int __init memory_tier_init(void)
 		panic("%s() failed to allocate default DRAM tier\n", __func__);
 
 	/*
-	 * Look at all the existing N_MEMORY nodes and add them to
-	 * default memory tier or to a tier if we already have memory
-	 * types assigned.
+	 * Record nodes with memory and CPU to set default DRAM performance.
 	 */
-	for_each_node_state(node, N_MEMORY) {
-		if (!node_state(node, N_CPU))
-			/*
-			 * Defer memory tier initialization on
-			 * CPUless numa nodes. These will be initialized
-			 * after firmware and devices are initialized.
-			 */
-			continue;
-
-		memtier = set_node_memory_tier(node);
-		if (IS_ERR(memtier))
-			/*
-			 * Continue with memtiers we are able to setup
-			 */
-			break;
-	}
-	establish_demotion_targets();
-	mutex_unlock(&memory_tier_lock);
+	for_each_node_state(node, N_MEMORY)
+		if (node_state(node, N_CPU))
+			node_set(node, default_dram_nodes);
 
 	hotplug_memory_notifier(memtier_hotplug_callback, MEMTIER_HOTPLUG_PRI);
 	return 0;
-- 
Ho-Ren (Jack) Chuang

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