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

Huang, Ying
2022-07-29T06:20:58Z

"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.

> + .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.

Best Regards,
Huang, Ying

> for (i = 0; i < dev_dax->nr_range; i++) {
> struct range range;
>
> diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
> index 976f43a5e3be..4f4baf0bf430 100644
> --- a/include/linux/memory-tiers.h
> +++ b/include/linux/memory-tiers.h
> @@ -2,6 +2,8 @@
> #ifndef _LINUX_MEMORY_TIERS_H
> #define _LINUX_MEMORY_TIERS_H
>
> +#include <linux/types.h>
> +#include <linux/nodemask.h>
> /*
> * Each tier cover a abstrace distance chunk size of 128
> */
> @@ -15,12 +17,27 @@
> #define MEMTIER_ADISTANCE_PMEM (1 << MEMTIER_CHUNK_BITS)
> #define MEMTIER_HOTPLUG_PRIO 100
>
> +struct memory_tier;
> +struct memory_dev_type {
> + /* list of memory types that are are part of same tier as this type */
> + struct list_head tier_sibiling;
> + /* abstract distance for this specific memory type */
> + int adistance;
> + /* Nodes of same abstract distance */
> + nodemask_t nodes;
> + struct memory_tier *memtier;
> +};
> +
> #ifdef CONFIG_NUMA
> -#include <linux/types.h>
> extern bool numa_demotion_enabled;
> +struct memory_dev_type *init_node_memory_type(int node, struct memory_dev_type *default_type);
>
> #else
>
> #define numa_demotion_enabled false
> +static inline struct memory_dev_type *init_node_memory_type(int node, struct memory_dev_type *default_type)
> +{
> + return ERR_PTR(-EINVAL);
> +}
> #endif /* CONFIG_NUMA */
> #endif /* _LINUX_MEMORY_TIERS_H */
> diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
> index c9854a394d9b..109be75fa554 100644
> --- a/mm/memory-tiers.c
> +++ b/mm/memory-tiers.c
> @@ -1,6 +1,4 @@
> // SPDX-License-Identifier: GPL-2.0
> -#include <linux/types.h>
> -#include <linux/nodemask.h>
> #include <linux/slab.h>
> #include <linux/lockdep.h>
> #include <linux/memory.h>
> @@ -19,16 +17,6 @@ struct memory_tier {
> int adistance_start;
> };
>
> -struct memory_dev_type {
> - /* list of memory types that are are part of same tier as this type */
> - struct list_head tier_sibiling;
> - /* abstract distance for this specific memory type */
> - int adistance;
> - /* Nodes of same abstract distance */
> - nodemask_t nodes;
> - struct memory_tier *memtier;
> -};
> -
> static DEFINE_MUTEX(memory_tier_lock);
> static LIST_HEAD(memory_tiers);
> struct memory_dev_type *node_memory_types[MAX_NUMNODES];
> @@ -141,6 +129,22 @@ static void clear_node_memory_tier(int node)
> mutex_unlock(&memory_tier_lock);
> }
>
> +struct memory_dev_type *init_node_memory_type(int node, struct memory_dev_type *default_type)
> +{
> + struct memory_dev_type *mem_type;
> +
> + mutex_lock(&memory_tier_lock);
> + if (node_memory_types[node]) {
> + mem_type = node_memory_types[node];
> + } else {
> + node_memory_types[node] = default_type;
> + node_set(node, default_type->nodes);
> + mem_type = default_type;
> + }
> + mutex_unlock(&memory_tier_lock);
> + return mem_type;
> +}
> +
> static int __meminit memtier_hotplug_callback(struct notifier_block *self,
> unsigned long action, void *_arg)
> {