mm/demotion: build demotion targets based on explicit memory tiers

void destroy_memory_type(struct memory_dev_type *memtype);

void init_node_memory_type(int node, struct memory_dev_type *default_type);

void clear_node_memory_type(int node, struct memory_dev_type *memtype);

#ifdef CONFIG_MIGRATION

int next_demotion_node(int node);

#else

static inline int next_demotion_node(int node)

{

	return NUMA_NO_NODE;

}

#endif

#else

{

}

static inline int next_demotion_node(int node)

{

	return NUMA_NO_NODE;

}

#endif	/* CONFIG_NUMA */

#endif  /* _LINUX_MEMORY_TIERS_H */

#endif /* CONFIG_MIGRATION */

#if defined(CONFIG_MIGRATION) && defined(CONFIG_NUMA)

extern void set_migration_target_nodes(void);

extern void migrate_on_reclaim_init(void);

extern int next_demotion_node(int node);

#else

static inline void set_migration_target_nodes(void) {}

static inline void migrate_on_reclaim_init(void) {}

static inline int next_demotion_node(int node)

{

        return NUMA_NO_NODE;

}

#endif

#ifdef CONFIG_COMPACTION

bool PageMovable(struct page *page);

void __SetPageMovable(struct page *page, const struct movable_operations *ops);

#include <linux/memory.h>

#include <linux/memory-tiers.h>

#include "internal.h"

struct memory_tier {

	/* hierarchy of memory tiers */

	struct list_head list;

	int adistance_start;

};

struct demotion_nodes {

	nodemask_t preferred;

};

struct node_memory_type_map {

	struct memory_dev_type *memtype;

	int map_count;

static LIST_HEAD(memory_tiers);

static struct node_memory_type_map node_memory_types[MAX_NUMNODES];

static struct memory_dev_type *default_dram_type;

#ifdef CONFIG_MIGRATION

/*

 * node_demotion[] examples:

 *

 * Example 1:

 *

 * Node 0 & 1 are CPU + DRAM nodes, node 2 & 3 are PMEM nodes.

 *

 * node distances:

 * node   0    1    2    3

 *    0  10   20   30   40

 *    1  20   10   40   30

 *    2  30   40   10   40

 *    3  40   30   40   10

 *

 * memory_tiers0 = 0-1

 * memory_tiers1 = 2-3

 *

 * node_demotion[0].preferred = 2

 * node_demotion[1].preferred = 3

 * node_demotion[2].preferred = <empty>

 * node_demotion[3].preferred = <empty>

 *

 * Example 2:

 *

 * Node 0 & 1 are CPU + DRAM nodes, node 2 is memory-only DRAM node.

 *

 * node distances:

 * node   0    1    2

 *    0  10   20   30

 *    1  20   10   30

 *    2  30   30   10

 *

 * memory_tiers0 = 0-2

 *

 * node_demotion[0].preferred = <empty>

 * node_demotion[1].preferred = <empty>

 * node_demotion[2].preferred = <empty>

 *

 * Example 3:

 *

 * Node 0 is CPU + DRAM nodes, Node 1 is HBM node, node 2 is PMEM node.

 *

 * node distances:

 * node   0    1    2

 *    0  10   20   30

 *    1  20   10   40

 *    2  30   40   10

 *

 * memory_tiers0 = 1

 * memory_tiers1 = 0

 * memory_tiers2 = 2

 *

 * node_demotion[0].preferred = 2

 * node_demotion[1].preferred = 0

 * node_demotion[2].preferred = <empty>

 *

 */

static struct demotion_nodes *node_demotion __read_mostly;

#endif /* CONFIG_MIGRATION */

static struct memory_tier *find_create_memory_tier(struct memory_dev_type *memtype)

{

	return new_memtier;

}

static struct memory_tier *__node_get_memory_tier(int node)

{

	struct memory_dev_type *memtype;

	memtype = node_memory_types[node];

	if (memtype && node_isset(node, memtype->nodes))

		return memtype->memtier;

	return NULL;

}

#ifdef CONFIG_MIGRATION

/**

 * next_demotion_node() - Get the next node in the demotion path

 * @node: The starting node to lookup the next node

 *

 * Return: node id for next memory node in the demotion path hierarchy

 * from @node; NUMA_NO_NODE if @node is terminal.  This does not keep

 * @node online or guarantee that it *continues* to be the next demotion

 * target.

 */

int next_demotion_node(int node)

{

	struct demotion_nodes *nd;

	int target;

	if (!node_demotion)

		return NUMA_NO_NODE;

	nd = &node_demotion[node];

	/*

	 * node_demotion[] is updated without excluding this

	 * function from running.

	 *

	 * Make sure to use RCU over entire code blocks if

	 * node_demotion[] reads need to be consistent.

	 */

	rcu_read_lock();

	/*

	 * If there are multiple target nodes, just select one

	 * target node randomly.

	 *

	 * In addition, we can also use round-robin to select

	 * target node, but we should introduce another variable

	 * for node_demotion[] to record last selected target node,

	 * that may cause cache ping-pong due to the changing of

	 * last target node. Or introducing per-cpu data to avoid

	 * caching issue, which seems more complicated. So selecting

	 * target node randomly seems better until now.

	 */

	target = node_random(&nd->preferred);

	rcu_read_unlock();

	return target;

}

static void disable_all_demotion_targets(void)

{

	int node;

	for_each_node_state(node, N_MEMORY)

		node_demotion[node].preferred = NODE_MASK_NONE;

	/*

	 * Ensure that the "disable" is visible across the system.

	 * Readers will see either a combination of before+disable

	 * state or disable+after.  They will never see before and

	 * after state together.

	 */

	synchronize_rcu();

}

static __always_inline nodemask_t get_memtier_nodemask(struct memory_tier *memtier)

{

	nodemask_t nodes = NODE_MASK_NONE;

	struct memory_dev_type *memtype;

	list_for_each_entry(memtype, &memtier->memory_types, tier_sibiling)

		nodes_or(nodes, nodes, memtype->nodes);

	return nodes;

}

/*

 * Find an automatic demotion target for all memory

 * nodes. Failing here is OK.  It might just indicate

 * being at the end of a chain.

 */

static void establish_demotion_targets(void)

{

	struct memory_tier *memtier;

	struct demotion_nodes *nd;

	int target = NUMA_NO_NODE, node;

	int distance, best_distance;

	nodemask_t tier_nodes;

	lockdep_assert_held_once(&memory_tier_lock);

	if (!node_demotion || !IS_ENABLED(CONFIG_MIGRATION))

		return;

	disable_all_demotion_targets();

	for_each_node_state(node, N_MEMORY) {

		best_distance = -1;

		nd = &node_demotion[node];

		memtier = __node_get_memory_tier(node);

		if (!memtier || list_is_last(&memtier->list, &memory_tiers))

			continue;

		/*

		 * Get the lower memtier to find the  demotion node list.

		 */

		memtier = list_next_entry(memtier, list);

		tier_nodes = get_memtier_nodemask(memtier);

		/*

		 * find_next_best_node, use 'used' nodemask as a skip list.

		 * Add all memory nodes except the selected memory tier

		 * nodelist to skip list so that we find the best node from the

		 * memtier nodelist.

		 */

		nodes_andnot(tier_nodes, node_states[N_MEMORY], tier_nodes);

		/*

		 * Find all the nodes in the memory tier node list of same best distance.

		 * add them to the preferred mask. We randomly select between nodes

		 * in the preferred mask when allocating pages during demotion.

		 */

		do {

			target = find_next_best_node(node, &tier_nodes);

			if (target == NUMA_NO_NODE)

				break;

			distance = node_distance(node, target);

			if (distance == best_distance || best_distance == -1) {

				best_distance = distance;

				node_set(target, nd->preferred);

			} else {

				break;

			}

		} while (1);

	}

}

#else

static inline void disable_all_demotion_targets(void) {}

static inline void establish_demotion_targets(void) {}

#endif /* CONFIG_MIGRATION */

static inline void __init_node_memory_type(int node, struct memory_dev_type *memtype)

{

	if (!node_memory_types[node].memtype)

	return memtier;

}

static struct memory_tier *__node_get_memory_tier(int node)

{

	struct memory_dev_type *memtype;

	memtype = node_memory_types[node];

	if (memtype && node_isset(node, memtype->nodes))

		return memtype->memtier;

	return NULL;

}

static void destroy_memory_tier(struct memory_tier *memtier)

{

	list_del(&memtier->list);

static int __meminit memtier_hotplug_callback(struct notifier_block *self,

					      unsigned long action, void *_arg)

{

	struct memory_tier *memtier;

	struct memory_notify *arg = _arg;

	/*

	switch (action) {

	case MEM_OFFLINE:

		mutex_lock(&memory_tier_lock);

		clear_node_memory_tier(arg->status_change_nid);

		if (clear_node_memory_tier(arg->status_change_nid))

			establish_demotion_targets();

		mutex_unlock(&memory_tier_lock);

		break;

	case MEM_ONLINE:

		mutex_lock(&memory_tier_lock);

		set_node_memory_tier(arg->status_change_nid);

		memtier = set_node_memory_tier(arg->status_change_nid);

		if (!IS_ERR(memtier))

			establish_demotion_targets();

		mutex_unlock(&memory_tier_lock);

		break;

	}

	int node;

	struct memory_tier *memtier;

#ifdef CONFIG_MIGRATION

	node_demotion = kcalloc(nr_node_ids, sizeof(struct demotion_nodes),

				GFP_KERNEL);

	WARN_ON(!node_demotion);

#endif

	mutex_lock(&memory_tier_lock);

	/*

	 * For now we can have 4 faster memory tiers with smaller adistance

			 */

			break;

	}

	establish_demotion_targets();

	mutex_unlock(&memory_tier_lock);

	hotplug_memory_notifier(memtier_hotplug_callback, MEMTIER_HOTPLUG_PRIO);

	return 0;

}

#endif /* CONFIG_NUMA_BALANCING */

/*

 * node_demotion[] example:

 *

 * Consider a system with two sockets.  Each socket has

 * three classes of memory attached: fast, medium and slow.

 * Each memory class is placed in its own NUMA node.  The

 * CPUs are placed in the node with the "fast" memory.  The

 * 6 NUMA nodes (0-5) might be split among the sockets like

 * this:

 *

 *	Socket A: 0, 1, 2

 *	Socket B: 3, 4, 5

 *

 * When Node 0 fills up, its memory should be migrated to

 * Node 1.  When Node 1 fills up, it should be migrated to

 * Node 2.  The migration path start on the nodes with the

 * processors (since allocations default to this node) and

 * fast memory, progress through medium and end with the

 * slow memory:

 *

 *	0 -> 1 -> 2 -> stop

 *	3 -> 4 -> 5 -> stop

 *

 * This is represented in the node_demotion[] like this:

 *

 *	{  nr=1, nodes[0]=1 }, // Node 0 migrates to 1

 *	{  nr=1, nodes[0]=2 }, // Node 1 migrates to 2

 *	{  nr=0, nodes[0]=-1 }, // Node 2 does not migrate

 *	{  nr=1, nodes[0]=4 }, // Node 3 migrates to 4

 *	{  nr=1, nodes[0]=5 }, // Node 4 migrates to 5

 *	{  nr=0, nodes[0]=-1 }, // Node 5 does not migrate

 *

 * Moreover some systems may have multiple slow memory nodes.

 * Suppose a system has one socket with 3 memory nodes, node 0

 * is fast memory type, and node 1/2 both are slow memory

 * type, and the distance between fast memory node and slow

 * memory node is same. So the migration path should be:

 *

 *	0 -> 1/2 -> stop

 *

 * This is represented in the node_demotion[] like this:

 *	{ nr=2, {nodes[0]=1, nodes[1]=2} }, // Node 0 migrates to node 1 and node 2

 *	{ nr=0, nodes[0]=-1, }, // Node 1 dose not migrate

 *	{ nr=0, nodes[0]=-1, }, // Node 2 does not migrate

 */

/*

 * Writes to this array occur without locking.  Cycles are

 * not allowed: Node X demotes to Y which demotes to X...

 *

 * If multiple reads are performed, a single rcu_read_lock()

 * must be held over all reads to ensure that no cycles are

 * observed.

 */

#define DEFAULT_DEMOTION_TARGET_NODES 15

#if MAX_NUMNODES < DEFAULT_DEMOTION_TARGET_NODES

#define DEMOTION_TARGET_NODES	(MAX_NUMNODES - 1)

#else

#define DEMOTION_TARGET_NODES	DEFAULT_DEMOTION_TARGET_NODES

#endif

struct demotion_nodes {

	unsigned short nr;

	short nodes[DEMOTION_TARGET_NODES];

};

static struct demotion_nodes *node_demotion __read_mostly;

/**

 * next_demotion_node() - Get the next node in the demotion path

 * @node: The starting node to lookup the next node

 *

 * Return: node id for next memory node in the demotion path hierarchy

 * from @node; NUMA_NO_NODE if @node is terminal.  This does not keep

 * @node online or guarantee that it *continues* to be the next demotion

 * target.

 */

int next_demotion_node(int node)

{

	struct demotion_nodes *nd;

	unsigned short target_nr, index;

	int target;

	if (!node_demotion)

		return NUMA_NO_NODE;

	nd = &node_demotion[node];

	/*

	 * node_demotion[] is updated without excluding this

	 * function from running.  RCU doesn't provide any

	 * compiler barriers, so the READ_ONCE() is required

	 * to avoid compiler reordering or read merging.

	 *

	 * Make sure to use RCU over entire code blocks if

	 * node_demotion[] reads need to be consistent.

	 */

	rcu_read_lock();

	target_nr = READ_ONCE(nd->nr);

	switch (target_nr) {

	case 0:

		target = NUMA_NO_NODE;

		goto out;

	case 1:

		index = 0;

		break;

	default:

		/*

		 * If there are multiple target nodes, just select one

		 * target node randomly.

		 *

		 * In addition, we can also use round-robin to select

		 * target node, but we should introduce another variable

		 * for node_demotion[] to record last selected target node,

		 * that may cause cache ping-pong due to the changing of

		 * last target node. Or introducing per-cpu data to avoid

		 * caching issue, which seems more complicated. So selecting

		 * target node randomly seems better until now.

		 */

		index = get_random_int() % target_nr;

		break;

	}

	target = READ_ONCE(nd->nodes[index]);

out:

	rcu_read_unlock();

	return target;

}

/* Disable reclaim-based migration. */

static void __disable_all_migrate_targets(void)

{

	int node, i;

	if (!node_demotion)

		return;

	for_each_online_node(node) {

		node_demotion[node].nr = 0;

		for (i = 0; i < DEMOTION_TARGET_NODES; i++)

			node_demotion[node].nodes[i] = NUMA_NO_NODE;

	}

}

static void disable_all_migrate_targets(void)

{

	__disable_all_migrate_targets();

	/*

	 * Ensure that the "disable" is visible across the system.

	 * Readers will see either a combination of before+disable

	 * state or disable+after.  They will never see before and

	 * after state together.

	 *

	 * The before+after state together might have cycles and

	 * could cause readers to do things like loop until this

	 * function finishes.  This ensures they can only see a

	 * single "bad" read and would, for instance, only loop

	 * once.

	 */

	synchronize_rcu();

}

/*

 * Find an automatic demotion target for 'node'.

 * Failing here is OK.  It might just indicate

 * being at the end of a chain.

 */

static int establish_migrate_target(int node, nodemask_t *used,

				    int best_distance)

{

	int migration_target, index, val;

	struct demotion_nodes *nd;

	if (!node_demotion)

		return NUMA_NO_NODE;

	nd = &node_demotion[node];

	migration_target = find_next_best_node(node, used);

	if (migration_target == NUMA_NO_NODE)

		return NUMA_NO_NODE;

	/*

	 * If the node has been set a migration target node before,

	 * which means it's the best distance between them. Still

	 * check if this node can be demoted to other target nodes

	 * if they have a same best distance.

	 */

	if (best_distance != -1) {

		val = node_distance(node, migration_target);

		if (val > best_distance)

			goto out_clear;

	}

	index = nd->nr;

	if (WARN_ONCE(index >= DEMOTION_TARGET_NODES,

		      "Exceeds maximum demotion target nodes\n"))

		goto out_clear;

	nd->nodes[index] = migration_target;

	nd->nr++;

	return migration_target;

out_clear:

	node_clear(migration_target, *used);

	return NUMA_NO_NODE;

}

/*

 * When memory fills up on a node, memory contents can be

 * automatically migrated to another node instead of

 * discarded at reclaim.

 *

 * Establish a "migration path" which will start at nodes

 * with CPUs and will follow the priorities used to build the

 * page allocator zonelists.

 *

 * The difference here is that cycles must be avoided.  If

 * node0 migrates to node1, then neither node1, nor anything

 * node1 migrates to can migrate to node0. Also one node can

 * be migrated to multiple nodes if the target nodes all have

 * a same best-distance against the source node.

 *

 * This function can run simultaneously with readers of

 * node_demotion[].  However, it can not run simultaneously

 * with itself.  Exclusion is provided by memory hotplug events

 * being single-threaded.

 */

static void __set_migration_target_nodes(void)

{

	nodemask_t next_pass;

	nodemask_t this_pass;

	nodemask_t used_targets = NODE_MASK_NONE;

	int node, best_distance;

	/*

	 * Avoid any oddities like cycles that could occur

	 * from changes in the topology.  This will leave

	 * a momentary gap when migration is disabled.

	 */

	disable_all_migrate_targets();

	/*

	 * Allocations go close to CPUs, first.  Assume that

	 * the migration path starts at the nodes with CPUs.

	 */

	next_pass = node_states[N_CPU];

again:

	this_pass = next_pass;

	next_pass = NODE_MASK_NONE;

	/*

	 * To avoid cycles in the migration "graph", ensure

	 * that migration sources are not future targets by

	 * setting them in 'used_targets'.  Do this only

	 * once per pass so that multiple source nodes can

	 * share a target node.

	 *

	 * 'used_targets' will become unavailable in future

	 * passes.  This limits some opportunities for

	 * multiple source nodes to share a destination.

	 */

	nodes_or(used_targets, used_targets, this_pass);

	for_each_node_mask(node, this_pass) {

		best_distance = -1;

		/*

		 * Try to set up the migration path for the node, and the target

		 * migration nodes can be multiple, so doing a loop to find all

		 * the target nodes if they all have a best node distance.

		 */

		do {

			int target_node =

				establish_migrate_target(node, &used_targets,

							 best_distance);

			if (target_node == NUMA_NO_NODE)

				break;

			if (best_distance == -1)

				best_distance = node_distance(node, target_node);

			/*

			 * Visit targets from this pass in the next pass.

			 * Eventually, every node will have been part of

			 * a pass, and will become set in 'used_targets'.

			 */

			node_set(target_node, next_pass);

		} while (1);

	}

	/*

	 * 'next_pass' contains nodes which became migration

	 * targets in this pass.  Make additional passes until

	 * no more migrations targets are available.

	 */

	if (!nodes_empty(next_pass))

		goto again;

}

/*

 * For callers that do not hold get_online_mems() already.

 */

void set_migration_target_nodes(void)

{

	get_online_mems();

	__set_migration_target_nodes();

	put_online_mems();

}

/*

 * This leaves migrate-on-reclaim transiently disabled between

 * the MEM_GOING_OFFLINE and MEM_OFFLINE events.  This runs

 * whether reclaim-based migration is enabled or not, which

 * ensures that the user can turn reclaim-based migration at

 * any time without needing to recalculate migration targets.

 *

 * These callbacks already hold get_online_mems().  That is why

 * __set_migration_target_nodes() can be used as opposed to

 * set_migration_target_nodes().

 */

#ifdef CONFIG_MEMORY_HOTPLUG

static int __meminit migrate_on_reclaim_callback(struct notifier_block *self,

						 unsigned long action, void *_arg)

{

	struct memory_notify *arg = _arg;

	/*

	 * Only update the node migration order when a node is

	 * changing status, like online->offline.  This avoids

	 * the overhead of synchronize_rcu() in most cases.

	 */

	if (arg->status_change_nid < 0)

		return notifier_from_errno(0);

	switch (action) {

	case MEM_GOING_OFFLINE:

		/*

		 * Make sure there are not transient states where

		 * an offline node is a migration target.  This

		 * will leave migration disabled until the offline

		 * completes and the MEM_OFFLINE case below runs.

		 */

		disable_all_migrate_targets();

		break;

	case MEM_OFFLINE:

	case MEM_ONLINE:

		/*

		 * Recalculate the target nodes once the node

		 * reaches its final state (online or offline).

		 */

		__set_migration_target_nodes();

		break;

	case MEM_CANCEL_OFFLINE:

		/*

		 * MEM_GOING_OFFLINE disabled all the migration

		 * targets.  Reenable them.

		 */

		__set_migration_target_nodes();

		break;

	case MEM_GOING_ONLINE:

	case MEM_CANCEL_ONLINE:

		break;

	}

	return notifier_from_errno(0);

}

#endif

void __init migrate_on_reclaim_init(void)

{

	node_demotion = kcalloc(nr_node_ids,

				sizeof(struct demotion_nodes),

				GFP_KERNEL);

	WARN_ON(!node_demotion);

#ifdef CONFIG_MEMORY_HOTPLUG

	hotplug_memory_notifier(migrate_on_reclaim_callback, 100);

#endif

	/*

	 * At this point, all numa nodes with memory/CPus have their state

	 * properly set, so we can build the demotion order now.

	 * Let us hold the cpu_hotplug lock just, as we could possibily have

	 * CPU hotplug events during boot.

	 */

	cpus_read_lock();

	set_migration_target_nodes();

	cpus_read_unlock();

}

#endif /* CONFIG_NUMA */

#include <linux/mm_inline.h>

#include <linux/page_ext.h>

#include <linux/page_owner.h>

#include <linux/migrate.h>

#include "internal.h"

	if (!node_state(cpu_to_node(cpu), N_CPU)) {

		node_set_state(cpu_to_node(cpu), N_CPU);

		set_migration_target_nodes();

	}

	return 0;

		return 0;

	node_clear_state(node, N_CPU);

	set_migration_target_nodes();

	return 0;

}

	start_shepherd_timer();

#endif

	migrate_on_reclaim_init();

#ifdef CONFIG_PROC_FS

	proc_create_seq("buddyinfo", 0444, NULL, &fragmentation_op);

	proc_create_seq("pagetypeinfo", 0400, NULL, &pagetypeinfo_op);