Re: [RFC PATCH v4 2/7] mm/demotion: Expose per node memory tier to sysfs

[Aneesh Kumar K V <aneesh.kumar@linux.ibm.com>]

On 6/8/22 12:48 PM, Ying Huang wrote:
> On Fri, 2022-05-27 at 17:55 +0530, Aneesh Kumar K.V wrote:
>> From: Jagdish Gediya <jvgediya@linux.ibm.com>
>>
>> Add support to read/write the memory tierindex for a NUMA node.
>>
>> /sys/devices/system/node/nodeN/memtier
>>
>> where N = node id
>>
>> When read, It list the memory tier that the node belongs to.
>>
>> When written, the kernel moves the node into the specified
>> memory tier, the tier assignment of all other nodes are not
>> affected.
>>
>> If the memory tier does not exist, writing to the above file
>> create the tier and assign the NUMA node to that tier.
>>
>> mutex memory_tier_lock is introduced to protect memory tier
>> related chanegs as it can happen from sysfs as well on hot
>> plug events.
>>
>> Signed-off-by: Jagdish Gediya <jvgediya@linux.ibm.com>
>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
>> ---
>>   drivers/base/node.c     |  35 ++++++++++++++
>>   include/linux/migrate.h |   4 +-
>>   mm/migrate.c            | 103 ++++++++++++++++++++++++++++++++++++++++
>>   3 files changed, 141 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/base/node.c b/drivers/base/node.c
>> index ec8bb24a5a22..cf4a58446d8c 100644
>> --- a/drivers/base/node.c
>> +++ b/drivers/base/node.c
>> @@ -20,6 +20,7 @@
>>   #include <linux/pm_runtime.h>
>>   #include <linux/swap.h>
>>   #include <linux/slab.h>
>> +#include <linux/migrate.h>
>>   
>>
>>
>>
>>   static struct bus_type node_subsys = {
>>   	.name = "node",
>> @@ -560,11 +561,45 @@ static ssize_t node_read_distance(struct device *dev,
>>   }
>>   static DEVICE_ATTR(distance, 0444, node_read_distance, NULL);
>>   
>>
>>
>>
>> +#ifdef CONFIG_TIERED_MEMORY
>> +static ssize_t memtier_show(struct device *dev,
>> +			    struct device_attribute *attr,
>> +			    char *buf)
>> +{
>> +	int node = dev->id;
>> +
>> +	return sysfs_emit(buf, "%d\n", node_get_memory_tier(node));
>> +}
>> +
>> +static ssize_t memtier_store(struct device *dev,
>> +			     struct device_attribute *attr,
>> +			     const char *buf, size_t count)
>> +{
>> +	unsigned long tier;
>> +	int node = dev->id;
>> +
>> +	int ret = kstrtoul(buf, 10, &tier);
>> +	if (ret)
>> +		return ret;
>> +
>> +	ret = node_reset_memory_tier(node, tier);
>> +	if (ret)
>> +		return ret;
>> +
>> +	return count;
>> +}
>> +
>> +static DEVICE_ATTR_RW(memtier);
>> +#endif
>> +
>>   static struct attribute *node_dev_attrs[] = {
>>   	&dev_attr_meminfo.attr,
>>   	&dev_attr_numastat.attr,
>>   	&dev_attr_distance.attr,
>>   	&dev_attr_vmstat.attr,
>> +#ifdef CONFIG_TIERED_MEMORY
>> +	&dev_attr_memtier.attr,
>> +#endif
>>   	NULL
>>   };
>>   
>>
>>
>>
>> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
>> index 0ec653623565..d37d1d5dee82 100644
>> --- a/include/linux/migrate.h
>> +++ b/include/linux/migrate.h
>> @@ -177,13 +177,15 @@ enum memory_tier_type {
>>   };
>>   
>>
>>
>>
>>   int next_demotion_node(int node);
>> -
>>   extern void migrate_on_reclaim_init(void);
>>   #ifdef CONFIG_HOTPLUG_CPU
>>   extern void set_migration_target_nodes(void);
>>   #else
>>   static inline void set_migration_target_nodes(void) {}
>>   #endif
>> +int node_get_memory_tier(int node);
>> +int node_set_memory_tier(int node, int tier);
>> +int node_reset_memory_tier(int node, int tier);
>>   #else
>>   #define numa_demotion_enabled	false
>>   static inline int next_demotion_node(int node)
>> diff --git a/mm/migrate.c b/mm/migrate.c
>> index f28ee93fb017..304559ba3372 100644
>> --- a/mm/migrate.c
>> +++ b/mm/migrate.c
>> @@ -2132,6 +2132,7 @@ static struct bus_type memory_tier_subsys = {
>>   	.dev_name = "memtier",
>>   };
>>   
>>
>>
>>
>> +DEFINE_MUTEX(memory_tier_lock);
>>   static struct memory_tier *memory_tiers[MAX_MEMORY_TIERS];
>>   
>>
>>
>>
>>   static ssize_t nodelist_show(struct device *dev,
>> @@ -2225,6 +2226,108 @@ static const struct attribute_group *memory_tier_attr_groups[] = {
>>   	NULL,
>>   };
>>   
>>
>>
>>
>> +static int __node_get_memory_tier(int node)
>> +{
>> +	int tier;
>> +
>> +	for (tier = 0; tier < MAX_MEMORY_TIERS; tier++) {
>> +		if (memory_tiers[tier] && node_isset(node, memory_tiers[tier]->nodelist))
>> +			return tier;
>> +	}
>> +
>> +	return -1;
>> +}
>> +
>> +int node_get_memory_tier(int node)
>> +{
>> +	int tier;
>> +
>> +	/*
>> +	 * Make sure memory tier is not unregistered
>> +	 * while it is being read.
>> +	 */
>> +	mutex_lock(&memory_tier_lock);
>> +
>> +	tier = __node_get_memory_tier(node);
>> +
>> +	mutex_unlock(&memory_tier_lock);
>> +
>> +	return tier;
>> +}
>> +
>> +int __node_set_memory_tier(int node, int tier)
>> +{
>> +	int ret = 0;
>> +	/*
>> +	 * As register_memory_tier() for new tier can fail,
>> +	 * try it before modifying existing tier. register
>> +	 * tier makes tier visible in sysfs.
>> +	 */
>> +	if (!memory_tiers[tier]) {
>> +		ret = register_memory_tier(tier);
>> +		if (ret) {
>> +			goto out;
>> +		}
>> +	}
>> +
>> +	node_set(node, memory_tiers[tier]->nodelist);
>> +
>> +out:
>> +	return ret;
>> +}
>> +
>> +int node_reset_memory_tier(int node, int tier)
> 
> I think "reset" isn't a good name here.  Maybe something like "change"
> or "move"?
> 

how about node_update_memory_tier()?

-aneesh