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

[Ying Huang <ying.huang@intel.com>]

On Wed, 2022-06-08 at 13:55 +0530, Aneesh Kumar K V wrote:
> 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()?

That sounds OK for me.

Best Regards,
Huang, Ying