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    SubjectRe: [PATCH v11 4/8] mm/demotion/dax/kmem: Set node's abstract distance to MEMTIER_ADISTANCE_PMEM
    Date
    "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)
    > {

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