memory tiering: add abstract distance calculation algorithms management

Patch series "memory tiering: calculate abstract distance based on ACPI
HMAT", v4.

We have the explicit memory tiers framework to manage systems with
multiple types of memory, e.g., DRAM in DIMM slots and CXL memory devices.
Where, same kind of memory devices will be grouped into memory types,
then put into memory tiers.  To describe the performance of a memory type,
abstract distance is defined.  Which is in direct proportion to the memory
latency and inversely proportional to the memory bandwidth.  To keep the
code as simple as possible, fixed abstract distance is used in dax/kmem to
describe slow memory such as Optane DCPMM.

To support more memory types, in this series, we added the abstract
distance calculation algorithm management mechanism, provided a algorithm
implementation based on ACPI HMAT, and used the general abstract distance
calculation interface in dax/kmem driver.  So, dax/kmem can support HBM
(high bandwidth memory) in addition to the original Optane DCPMM.


This patch (of 4):

The abstract distance may be calculated by various drivers, such as ACPI
HMAT, CXL CDAT, etc.  While it may be used by various code which hot-add
memory node, such as dax/kmem etc.  To decouple the algorithm users and
the providers, the abstract distance calculation algorithms management
mechanism is implemented in this patch.  It provides interface for the
providers to register the implementation, and interface for the users.

Multiple algorithm implementations can cooperate via calculating abstract
distance for different memory nodes.  The preference of algorithm
implementations can be specified via priority (notifier_block.priority).

Link: https://lkml.kernel.org/r/20230926060628.265989-1-ying.huang@intel.com
Link: https://lkml.kernel.org/r/20230926060628.265989-2-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Tested-by: Bharata B Rao <bharata@amd.com>
Reviewed-by: Alistair Popple <apopple@nvidia.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Wei Xu <weixugc@google.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Rafael J Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
index 4fa178b50784..fddc59990644 100644
--- a/include/linux/memory-tiers.h
+++ b/include/linux/memory-tiers.h
@@ -6,6 +6,7 @@
 #include <linux/nodemask.h>
 #include <linux/kref.h>
 #include <linux/mmzone.h>
+#include <linux/notifier.h>
 /*
  * Each tier cover a abstrace distance chunk size of 128
  */
@@ -36,6 +37,9 @@ struct memory_dev_type *alloc_memory_type(int adistance);
 void put_memory_type(struct memory_dev_type *memtype);
 void init_node_memory_type(int node, struct memory_dev_type *default_type);
 void clear_node_memory_type(int node, struct memory_dev_type *memtype);
+int register_mt_adistance_algorithm(struct notifier_block *nb);
+int unregister_mt_adistance_algorithm(struct notifier_block *nb);
+int mt_calc_adistance(int node, int *adist);
 #ifdef CONFIG_MIGRATION
 int next_demotion_node(int node);
 void node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *targets);
@@ -97,5 +101,20 @@ static inline bool node_is_toptier(int node)
 {
 	return true;
 }
+
+static inline int register_mt_adistance_algorithm(struct notifier_block *nb)
+{
+	return 0;
+}
+
+static inline int unregister_mt_adistance_algorithm(struct notifier_block *nb)
+{
+	return 0;
+}
+
+static inline int mt_calc_adistance(int node, int *adist)
+{
+	return NOTIFY_DONE;
+}
 #endif	/* CONFIG_NUMA */
 #endif  /* _LINUX_MEMORY_TIERS_H */