[PATCH v1 1/1] memory tier: acpi/hmat: create CPUless memory tiers after obtaining HMAT info

[Ho-Ren (Jack) Chuang]

* Introduce `mt_init_with_hmat()`
We defer memory tier initialization for those CPUless NUMA nodes
until acquiring HMAT info. `mt_init_with_hmat()` is introduced to
post-create CPUless memory tiers after obtaining HMAT info.
It iterates through each CPUless memory node, creating memory tiers if
necessary. Finally, it calculates demotion tables again at the end.

* Introduce `hmat_find_alloc_memory_type()`
Find or allocate a memory type in the `hmat_memory_types` list.

* Make `set_node_memory_tier()` more generic
This function can also be used for setting other memory types for a node.
To do so, a new argument is added to specify a memory type.

* Handle cases where there is no HMAT when creating memory tiers
If no HMAT is specified, it falls back to using `default_dram_type`.

* Change adist calculation code to use another new lock, mt_perf_lock.
Iterating through CPUlist nodes requires holding the `memory_tier_lock`.
However, `mt_calc_adistance()` will end up trying to acquire the same lock,
leading to a potential deadlock. Therefore, we propose introducing a
standalone `mt_perf_lock` to protect `default_dram_perf`. This approach not
only avoids deadlock but also prevents holding a large lock simultaneously.

Signed-off-by: Ho-Ren (Jack) Chuang <horenchuang@bytedance.com>
Signed-off-by: Hao Xiang <hao.xiang@bytedance.com>
---
 drivers/acpi/numa/hmat.c     |  3 ++
 include/linux/memory-tiers.h |  6 +++
 mm/memory-tiers.c            | 76 ++++++++++++++++++++++++++++++++----
 3 files changed, 77 insertions(+), 8 deletions(-)

diff --git a/drivers/acpi/numa/hmat.c b/drivers/acpi/numa/hmat.c
index d6b85f0f6082..9f57338b3cb5 100644
--- a/drivers/acpi/numa/hmat.c
+++ b/drivers/acpi/numa/hmat.c
@@ -1038,6 +1038,9 @@ static __init int hmat_init(void)
        if (!hmat_set_default_dram_perf())
                register_mt_adistance_algorithm(&hmat_adist_nb);
 
+       /* Post-create CPUless memory tiers after getting HMAT info */
+       mt_init_with_hmat();
+
        return 0;
 out_put:
        hmat_free_structures();
diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
index 69e781900082..2f845e90c033 100644
--- a/include/linux/memory-tiers.h
+++ b/include/linux/memory-tiers.h
@@ -48,6 +48,7 @@ int mt_calc_adistance(int node, int *adist);
 int mt_set_default_dram_perf(int nid, struct access_coordinate *perf,
                             const char *source);
 int mt_perf_to_adistance(struct access_coordinate *perf, int *adist);
+void mt_init_with_hmat(void);
 #ifdef CONFIG_MIGRATION
 int next_demotion_node(int node);
 void node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *targets);
@@ -136,5 +137,10 @@ static inline int mt_perf_to_adistance(struct 
access_coordinate *perf, int *adis
 {
        return -EIO;
 }
+
+static inline void mt_init_with_hmat(void)
+{
+
+}
 #endif /* CONFIG_NUMA */
 #endif  /* _LINUX_MEMORY_TIERS_H */
diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
index 0537664620e5..7a0a579b3deb 100644
--- a/mm/memory-tiers.c
+++ b/mm/memory-tiers.c
@@ -35,7 +35,9 @@ struct node_memory_type_map {
 };
 
 static DEFINE_MUTEX(memory_tier_lock);
+static DEFINE_MUTEX(mt_perf_lock);
 static LIST_HEAD(memory_tiers);
+static LIST_HEAD(hmat_memory_types);
 static struct node_memory_type_map node_memory_types[MAX_NUMNODES];
 struct memory_dev_type *default_dram_type;
 
@@ -502,7 +504,7 @@ static inline void __init_node_memory_type(int node, struct 
memory_dev_type *mem
        }
 }
 
-static struct memory_tier *set_node_memory_tier(int node)
+static struct memory_tier *set_node_memory_tier(int node, struct 
memory_dev_type *new_memtype)
 {
        struct memory_tier *memtier;
        struct memory_dev_type *memtype;
@@ -514,7 +516,7 @@ static struct memory_tier *set_node_memory_tier(int node)
        if (!node_state(node, N_MEMORY))
                return ERR_PTR(-EINVAL);
 
-       __init_node_memory_type(node, default_dram_type);
+       __init_node_memory_type(node, new_memtype);
 
        memtype = node_memory_types[node].memtype;
        node_set(node, memtype->nodes);
@@ -623,6 +625,56 @@ void clear_node_memory_type(int node, struct 
memory_dev_type *memtype)
 }
 EXPORT_SYMBOL_GPL(clear_node_memory_type);
 
+static struct memory_dev_type *hmat_find_alloc_memory_type(int adist)
+{
+       bool found = false;
+       struct memory_dev_type *mtype;
+
+       list_for_each_entry(mtype, &hmat_memory_types, list) {
+               if (mtype->adistance == adist) {
+                       found = true;
+                       break;
+               }
+       }
+       if (!found) {
+               mtype = alloc_memory_type(adist);
+               if (!IS_ERR(mtype))
+                       list_add(&mtype->list, &hmat_memory_types);
+       }
+       return mtype;
+}
+
+static void mt_create_with_hmat(int node)
+{
+       struct memory_dev_type *mtype = NULL;
+       int adist = MEMTIER_ADISTANCE_DRAM;
+
+       mt_calc_adistance(node, &adist);
+       if (adist != MEMTIER_ADISTANCE_DRAM) {
+               mtype = hmat_find_alloc_memory_type(adist);
+               if (IS_ERR(mtype))
+                       pr_err("%s() failed to allocate a tier\n", __func__);
+       } else {
+               mtype = default_dram_type;
+       }
+
+       set_node_memory_tier(node, mtype);
+}
+
+void mt_init_with_hmat(void)
+{
+       int nid;
+
+       mutex_lock(&memory_tier_lock);
+       for_each_node_state(nid, N_MEMORY)
+               if (!node_state(nid, N_CPU))
+                       mt_create_with_hmat(nid);
+
+       establish_demotion_targets();
+       mutex_unlock(&memory_tier_lock);
+}
+EXPORT_SYMBOL_GPL(mt_init_with_hmat);
+
 static void dump_hmem_attrs(struct access_coordinate *coord, const char 
*prefix)
 {
        pr_info(
@@ -636,7 +688,7 @@ int mt_set_default_dram_perf(int nid, struct 
access_coordinate *perf,
 {
        int rc = 0;
 
-       mutex_lock(&memory_tier_lock);
+       mutex_lock(&mt_perf_lock);
        if (default_dram_perf_error) {
                rc = -EIO;
                goto out;
@@ -684,7 +736,7 @@ int mt_set_default_dram_perf(int nid, struct 
access_coordinate *perf,
        }
 
 out:
-       mutex_unlock(&memory_tier_lock);
+       mutex_unlock(&mt_perf_lock);
        return rc;
 }
 
@@ -700,7 +752,7 @@ int mt_perf_to_adistance(struct access_coordinate *perf, 
int *adist)
            perf->read_bandwidth + perf->write_bandwidth == 0)
                return -EINVAL;
 
-       mutex_lock(&memory_tier_lock);
+       mutex_lock(&mt_perf_lock);
        /*
         * The abstract distance of a memory node is in direct proportion to
         * its memory latency (read + write) and inversely proportional to its
@@ -713,7 +765,7 @@ int mt_perf_to_adistance(struct access_coordinate *perf, 
int *adist)
                (default_dram_perf.read_latency + 
default_dram_perf.write_latency) *
                (default_dram_perf.read_bandwidth + 
default_dram_perf.write_bandwidth) /
                (perf->read_bandwidth + perf->write_bandwidth);
-       mutex_unlock(&memory_tier_lock);
+       mutex_unlock(&mt_perf_lock);
 
        return 0;
 }
@@ -797,7 +849,7 @@ static int __meminit memtier_hotplug_callback(struct 
notifier_block *self,
                break;
        case MEM_ONLINE:
                mutex_lock(&memory_tier_lock);
-               memtier = set_node_memory_tier(arg->status_change_nid);
+               memtier = set_node_memory_tier(arg->status_change_nid, 
default_dram_type);
                if (!IS_ERR(memtier))
                        establish_demotion_targets();
                mutex_unlock(&memory_tier_lock);
@@ -836,7 +888,15 @@ static int __init memory_tier_init(void)
         * types assigned.
         */
        for_each_node_state(node, N_MEMORY) {
-               memtier = set_node_memory_tier(node);
+               if (!node_state(node, N_CPU))
+                       /*
+                        * Defer memory tier initialization on CPUless numa 
nodes.
+                        * These will be initialized when HMAT information is
+                        * available.
+                        */
+                       continue;
+
+               memtier = set_node_memory_tier(node, default_dram_type);
                if (IS_ERR(memtier))
                        /*
                         * Continue with memtiers we are able to setup
-- 
Hao Xiang and Ho-Ren (Jack) Chuang