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

Huang, Ying
2022-08-01T02:06:58Z

"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> writes:

> "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?

Or dax_pmem_type?

DAX is used to enumerate the memory device.

>
>>> + .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?

Because we set node_memorty_types[] in dev_dax_kmem_probe(), it's
natural to clear it in dev_dax_kmem_remove().

Best Regards,
Huang, Ying

> 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;