Re: [PATCH v11 4/8] mm/demotion/dax/kmem: Set node's abstract distance to MEMTIER_ADISTANCE_PMEM

Aneesh Kumar K.V
2022-07-29T07:20:23Z

"Huang, Ying" <ying.huang@intel.com> writes:

> "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> writes:
>
>> By default, all nodes are assigned to the default memory tier which
>> is the memory tier designated for nodes with DRAM
>>
>> Set dax kmem device node's tier to slower memory tier by assigning
>> abstract distance to MEMTIER_ADISTANCE_PMEM. PMEM tier
>> appears below the default memory tier in demotion order.
>>
>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
>> ---
>> drivers/dax/kmem.c | 9 +++++++++
>> include/linux/memory-tiers.h | 19 ++++++++++++++++++-
>> mm/memory-tiers.c | 28 ++++++++++++++++------------
>> 3 files changed, 43 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
>> index a37622060fff..6b0d5de9a3e9 100644
>> --- a/drivers/dax/kmem.c
>> +++ b/drivers/dax/kmem.c
>> @@ -11,6 +11,7 @@
>> #include <linux/fs.h>
>> #include <linux/mm.h>
>> #include <linux/mman.h>
>> +#include <linux/memory-tiers.h>
>> #include "dax-private.h"
>> #include "bus.h"
>>
>> @@ -41,6 +42,12 @@ struct dax_kmem_data {
>> struct resource *res[];
>> };
>>
>> +static struct memory_dev_type default_pmem_type = {
>
> Why is this named as default_pmem_type? We will not change the memory
> type of a node usually.
>

Any other suggestion? pmem_dev_type?

>> + .adistance = MEMTIER_ADISTANCE_PMEM,
>> + .tier_sibiling = LIST_HEAD_INIT(default_pmem_type.tier_sibiling),
>> + .nodes = NODE_MASK_NONE,
>> +};
>> +
>> static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
>> {
>> struct device *dev = &dev_dax->dev;
>> @@ -62,6 +69,8 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
>> return -EINVAL;
>> }
>>
>> + init_node_memory_type(numa_node, &default_pmem_type);
>> +
>
> The memory hot-add below may fail. So the error handling needs to be
> added.
>
> And, it appears that the memory type and memory tier of a node may be
> fully initialized here before NUMA hot-adding started. So I suggest to
> set node_memory_types[] here only. And set memory_dev_type->nodes in
> node hot-add callback. I think there is the proper place to complete
> the initialization.
>
> And, in theory dax/kmem.c can be unloaded. So we need to clear
> node_memory_types[] for nodes somewhere.
>

I guess by module exit we can be sure that all the memory managed
by dax/kmem is hotplugged out. How about something like below?

diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
index 6b0d5de9a3e9..eb4e158012a9 100644
--- a/drivers/dax/kmem.c
+++ b/drivers/dax/kmem.c
@@ -248,6 +248,7 @@ static void __exit dax_kmem_exit(void)
dax_driver_unregister(&device_dax_kmem_driver);
if (!any_hotremove_failed)
kfree_const(kmem_name);
+ unregister_memory_type(&default_pmem_type);
}

MODULE_AUTHOR("Intel Corporation");
diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
index fc6b7a14da51..8355baf5b8b4 100644
--- a/include/linux/memory-tiers.h
+++ b/include/linux/memory-tiers.h
@@ -31,6 +31,7 @@ struct memory_dev_type {
#ifdef CONFIG_NUMA
extern bool numa_demotion_enabled;
void init_node_memory_type(int node, struct memory_dev_type *default_type);
+void unregister_memory_type(struct memory_dev_type *memtype);
#ifdef CONFIG_MIGRATION
int next_demotion_node(int node);
void node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *targets);
@@ -57,6 +58,10 @@ static inline bool node_is_toptier(int node)
#define numa_demotion_enabled false
static inline void init_node_memory_type(int node, struct memory_dev_type *default_type)
{
+}
+
+static inline void unregister_memory_type(struct memory_dev_type *memtype)
+{

}

diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
index 064e0f932795..4d29ebd4c4f3 100644
--- a/mm/memory-tiers.c
+++ b/mm/memory-tiers.c
@@ -500,6 +500,28 @@ void init_node_memory_type(int node, struct memory_dev_type *default_type)
mutex_unlock(&memory_tier_lock);
}

+void unregister_memory_type(struct memory_dev_type *memtype)
+{
+ int node;
+ struct memory_tier *memtier = memtype->memtier;
+
+ mutex_lock(&memory_tier_lock);
+ for(node = 0; node < MAX_NUMNODES; node++) {
+ if (node_memory_types[node] == memtype) {
+ if (!nodes_empty(memtype->nodes))
+ WARN_ON(1);
+ node_memory_types[node] = NULL;
+ }
+ }
+
+ list_del(&memtype->tier_sibiling);
+ memtype->memtier = NULL;
+ if (list_empty(&memtier->memory_types))
+ destroy_memory_tier(memtier);
+
+ mutex_unlock(&memory_tier_lock);
+}
+
void update_node_adistance(int node, struct memory_dev_type *memtype)
{
pg_data_t *pgdat;