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Message-ID: <20250321173729.3175898-5-souravpanda@google.com>
Date: Fri, 21 Mar 2025 17:37:27 +0000
From: Sourav Panda <souravpanda@...gle.com>
To: mathieu.desnoyers@...icios.com, willy@...radead.org, david@...hat.com,
pasha.tatashin@...een.com, rientjes@...gle.com, akpm@...ux-foundation.org,
linux-mm@...ck.org, linux-kernel@...r.kernel.org, weixugc@...gle.com,
gthelen@...gle.com, souravpanda@...gle.com, surenb@...gle.com
Subject: [RFC PATCH 4/6] mm: create dedicated trees for SELECTIVE KSM partitions
Extend ksm to create dedicated unstable and stable trees for
each partition.
Signed-off-by: Sourav Panda <souravpanda@...gle.com>
---
mm/ksm.c | 165 +++++++++++++++++++++++++++++++++++++------------------
1 file changed, 111 insertions(+), 54 deletions(-)
diff --git a/mm/ksm.c b/mm/ksm.c
index 927e257c48b5..b575250aaf45 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -144,6 +144,28 @@ struct ksm_scan {
unsigned long seqnr;
};
+static struct kobject *ksm_base_kobj;
+
+struct partition_kobj {
+ struct kobject *kobj;
+ struct list_head list;
+ struct rb_root *root_stable_tree;
+ struct rb_root *root_unstable_tree;
+};
+
+static LIST_HEAD(partition_list);
+
+static struct partition_kobj *find_partition_by_kobj(struct kobject *kobj)
+{
+ struct partition_kobj *partition;
+
+ list_for_each_entry(partition, &partition_list, list) {
+ if (partition->kobj == kobj)
+ return partition;
+ }
+ return NULL;
+}
+
/**
* struct ksm_stable_node - node of the stable rbtree
* @node: rb node of this ksm page in the stable tree
@@ -182,6 +204,7 @@ struct ksm_stable_node {
#ifdef CONFIG_NUMA
int nid;
#endif
+ struct partition_kobj *partition;
};
/**
@@ -218,6 +241,7 @@ struct ksm_rmap_item {
struct hlist_node hlist;
};
};
+ struct partition_kobj *partition;
};
#define SEQNR_MASK 0x0ff /* low bits of unstable tree seqnr */
@@ -227,8 +251,6 @@ struct ksm_rmap_item {
/* The stable and unstable tree heads */
static struct rb_root one_stable_tree[1] = { RB_ROOT };
static struct rb_root one_unstable_tree[1] = { RB_ROOT };
-static struct rb_root *root_stable_tree = one_stable_tree;
-static struct rb_root *root_unstable_tree = one_unstable_tree;
/* Recently migrated nodes of stable tree, pending proper placement */
static LIST_HEAD(migrate_nodes);
@@ -555,7 +577,7 @@ static inline void stable_node_dup_del(struct ksm_stable_node *dup)
if (is_stable_node_dup(dup))
__stable_node_dup_del(dup);
else
- rb_erase(&dup->node, root_stable_tree + NUMA(dup->nid));
+ rb_erase(&dup->node, dup->partition->root_stable_tree + NUMA(dup->nid));
#ifdef CONFIG_DEBUG_VM
dup->head = NULL;
#endif
@@ -580,14 +602,20 @@ static inline void free_rmap_item(struct ksm_rmap_item *rmap_item)
kmem_cache_free(rmap_item_cache, rmap_item);
}
-static inline struct ksm_stable_node *alloc_stable_node(void)
+static inline struct ksm_stable_node *alloc_stable_node(struct partition_kobj *partition)
{
/*
* The allocation can take too long with GFP_KERNEL when memory is under
* pressure, which may lead to hung task warnings. Adding __GFP_HIGH
* grants access to memory reserves, helping to avoid this problem.
*/
- return kmem_cache_alloc(stable_node_cache, GFP_KERNEL | __GFP_HIGH);
+ struct ksm_stable_node *node = kmem_cache_alloc(stable_node_cache,
+ GFP_KERNEL | __GFP_HIGH);
+
+ if (node)
+ node->partition = partition;
+
+ return node;
}
static inline void free_stable_node(struct ksm_stable_node *stable_node)
@@ -777,9 +805,10 @@ static inline int get_kpfn_nid(unsigned long kpfn)
}
static struct ksm_stable_node *alloc_stable_node_chain(struct ksm_stable_node *dup,
- struct rb_root *root)
+ struct rb_root *root,
+ struct partition_kobj *partition)
{
- struct ksm_stable_node *chain = alloc_stable_node();
+ struct ksm_stable_node *chain = alloc_stable_node(partition);
VM_BUG_ON(is_stable_node_chain(dup));
if (likely(chain)) {
INIT_HLIST_HEAD(&chain->hlist);
@@ -1016,7 +1045,8 @@ static void remove_rmap_item_from_tree(struct ksm_rmap_item *rmap_item)
unsigned char age = get_rmap_item_age(rmap_item);
if (!age)
rb_erase(&rmap_item->node,
- root_unstable_tree + NUMA(rmap_item->nid));
+ rmap_item->partition->root_unstable_tree +
+ NUMA(rmap_item->nid));
ksm_pages_unshared--;
rmap_item->address &= PAGE_MASK;
}
@@ -1154,17 +1184,23 @@ static int remove_all_stable_nodes(void)
struct ksm_stable_node *stable_node, *next;
int nid;
int err = 0;
-
- for (nid = 0; nid < ksm_nr_node_ids; nid++) {
- while (root_stable_tree[nid].rb_node) {
- stable_node = rb_entry(root_stable_tree[nid].rb_node,
- struct ksm_stable_node, node);
- if (remove_stable_node_chain(stable_node,
- root_stable_tree + nid)) {
- err = -EBUSY;
- break; /* proceed to next nid */
+ struct partition_kobj *partition;
+ struct rb_root *root_stable_tree;
+
+ list_for_each_entry(partition, &partition_list, list) {
+ root_stable_tree = partition->root_stable_tree;
+
+ for (nid = 0; nid < ksm_nr_node_ids; nid++) {
+ while (root_stable_tree[nid].rb_node) {
+ stable_node = rb_entry(root_stable_tree[nid].rb_node,
+ struct ksm_stable_node, node);
+ if (remove_stable_node_chain(stable_node,
+ root_stable_tree + nid)) {
+ err = -EBUSY;
+ break; /* proceed to next nid */
+ }
+ cond_resched();
}
- cond_resched();
}
}
list_for_each_entry_safe(stable_node, next, &migrate_nodes, list) {
@@ -1802,7 +1838,8 @@ static __always_inline struct folio *chain(struct ksm_stable_node **s_n_d,
* This function returns the stable tree node of identical content if found,
* -EBUSY if the stable node's page is being migrated, NULL otherwise.
*/
-static struct folio *stable_tree_search(struct page *page)
+static struct folio *stable_tree_search(struct page *page,
+ struct partition_kobj *partition)
{
int nid;
struct rb_root *root;
@@ -1821,7 +1858,7 @@ static struct folio *stable_tree_search(struct page *page)
}
nid = get_kpfn_nid(folio_pfn(folio));
- root = root_stable_tree + nid;
+ root = partition->root_stable_tree + nid;
again:
new = &root->rb_node;
parent = NULL;
@@ -1991,7 +2028,7 @@ static struct folio *stable_tree_search(struct page *page)
VM_BUG_ON(is_stable_node_dup(stable_node_dup));
/* chain is missing so create it */
stable_node = alloc_stable_node_chain(stable_node_dup,
- root);
+ root, partition);
if (!stable_node)
return NULL;
}
@@ -2016,7 +2053,8 @@ static struct folio *stable_tree_search(struct page *page)
* This function returns the stable tree node just allocated on success,
* NULL otherwise.
*/
-static struct ksm_stable_node *stable_tree_insert(struct folio *kfolio)
+static struct ksm_stable_node *stable_tree_insert(struct folio *kfolio,
+ struct partition_kobj *partition)
{
int nid;
unsigned long kpfn;
@@ -2028,7 +2066,7 @@ static struct ksm_stable_node *stable_tree_insert(struct folio *kfolio)
kpfn = folio_pfn(kfolio);
nid = get_kpfn_nid(kpfn);
- root = root_stable_tree + nid;
+ root = partition->root_stable_tree + nid;
again:
parent = NULL;
new = &root->rb_node;
@@ -2067,7 +2105,7 @@ static struct ksm_stable_node *stable_tree_insert(struct folio *kfolio)
}
}
- stable_node_dup = alloc_stable_node();
+ stable_node_dup = alloc_stable_node(partition);
if (!stable_node_dup)
return NULL;
@@ -2082,7 +2120,8 @@ static struct ksm_stable_node *stable_tree_insert(struct folio *kfolio)
if (!is_stable_node_chain(stable_node)) {
struct ksm_stable_node *orig = stable_node;
/* chain is missing so create it */
- stable_node = alloc_stable_node_chain(orig, root);
+ stable_node = alloc_stable_node_chain(orig, root,
+ partition);
if (!stable_node) {
free_stable_node(stable_node_dup);
return NULL;
@@ -2121,7 +2160,7 @@ struct ksm_rmap_item *unstable_tree_search_insert(struct ksm_rmap_item *rmap_ite
int nid;
nid = get_kpfn_nid(page_to_pfn(page));
- root = root_unstable_tree + nid;
+ root = rmap_item->partition->root_unstable_tree + nid;
new = &root->rb_node;
while (*new) {
@@ -2291,7 +2330,7 @@ static void cmp_and_merge_page(struct page *page, struct ksm_rmap_item *rmap_ite
}
/* Start by searching for the folio in the stable tree */
- kfolio = stable_tree_search(page);
+ kfolio = stable_tree_search(page, rmap_item->partition);
if (&kfolio->page == page && rmap_item->head == stable_node) {
folio_put(kfolio);
return;
@@ -2344,7 +2383,8 @@ static void cmp_and_merge_page(struct page *page, struct ksm_rmap_item *rmap_ite
* node in the stable tree and add both rmap_items.
*/
folio_lock(kfolio);
- stable_node = stable_tree_insert(kfolio);
+ stable_node = stable_tree_insert(kfolio,
+ rmap_item->partition);
if (stable_node) {
stable_tree_append(tree_rmap_item, stable_node,
false);
@@ -2502,7 +2542,8 @@ static struct ksm_rmap_item *retrieve_rmap_item(struct page **page,
}
static void ksm_sync_merge(struct mm_struct *mm,
- unsigned long start, unsigned long end)
+ unsigned long start, unsigned long end,
+ struct partition_kobj *partition)
{
struct ksm_rmap_item *rmap_item;
struct page *page;
@@ -2510,6 +2551,7 @@ static void ksm_sync_merge(struct mm_struct *mm,
rmap_item = retrieve_rmap_item(&page, mm, start, end);
if (!rmap_item)
return;
+ rmap_item->partition = partition;
cmp_and_merge_page(page, rmap_item);
put_page(page);
}
@@ -3328,19 +3370,23 @@ static void ksm_check_stable_tree(unsigned long start_pfn,
struct ksm_stable_node *stable_node, *next;
struct rb_node *node;
int nid;
-
- for (nid = 0; nid < ksm_nr_node_ids; nid++) {
- node = rb_first(root_stable_tree + nid);
- while (node) {
- stable_node = rb_entry(node, struct ksm_stable_node, node);
- if (stable_node_chain_remove_range(stable_node,
- start_pfn, end_pfn,
- root_stable_tree +
- nid))
- node = rb_first(root_stable_tree + nid);
- else
- node = rb_next(node);
- cond_resched();
+ struct rb_root *root_stable_tree
+
+ list_for_each_entry(partition, &partition_list, list) {
+ root_stable_tree = partition->root_stable_tree;
+
+ for (nid = 0; nid < ksm_nr_node_ids; nid++) {
+ node = rb_first(root_stable_tree + nid);
+ while (node) {
+ stable_node = rb_entry(node, struct ksm_stable_node, node);
+ if (stable_node_chain_remove_range(stable_node,
+ start_pfn, end_pfn,
+ root_stable_tree + nid))
+ node = rb_first(root_stable_tree + nid);
+ else
+ node = rb_next(node);
+ cond_resched();
+ }
}
}
list_for_each_entry_safe(stable_node, next, &migrate_nodes, list) {
@@ -3551,6 +3597,7 @@ static ssize_t trigger_merge_store(struct kobject *kobj,
int ret;
struct task_struct *task;
struct mm_struct *mm;
+ struct partition_kobj *partition;
input = kstrdup(buf, GFP_KERNEL);
if (!input)
@@ -3583,9 +3630,13 @@ static ssize_t trigger_merge_store(struct kobject *kobj,
if (!mm)
return -EINVAL;
+ partition = find_partition_by_kobj(kobj);
+ if (!partition)
+ return -EINVAL;
+
mutex_lock(&ksm_thread_mutex);
wait_while_offlining();
- ksm_sync_merge(mm, start, end);
+ ksm_sync_merge(mm, start, end, partition);
mutex_unlock(&ksm_thread_mutex);
mmput(mm);
@@ -3606,6 +3657,8 @@ static ssize_t merge_across_nodes_store(struct kobject *kobj,
{
int err;
unsigned long knob;
+ struct rb_root *root_stable_tree;
+ struct partition_kobj *partition;
err = kstrtoul(buf, 10, &knob);
if (err)
@@ -3615,6 +3668,10 @@ static ssize_t merge_across_nodes_store(struct kobject *kobj,
mutex_lock(&ksm_thread_mutex);
wait_while_offlining();
+
+ partition = find_partition_by_kobj(kobj);
+ root_stable_tree = partition->root_stable_tree;
+
if (ksm_merge_across_nodes != knob) {
if (ksm_pages_shared || remove_all_stable_nodes())
err = -EBUSY;
@@ -3633,10 +3690,10 @@ static ssize_t merge_across_nodes_store(struct kobject *kobj,
if (!buf)
err = -ENOMEM;
else {
- root_stable_tree = buf;
- root_unstable_tree = buf + nr_node_ids;
+ partition->root_stable_tree = buf;
+ partition->root_unstable_tree = buf + nr_node_ids;
/* Stable tree is empty but not the unstable */
- root_unstable_tree[0] = one_unstable_tree[0];
+ partition->root_unstable_tree[0] = one_unstable_tree[0];
}
}
if (!err) {
@@ -3834,14 +3891,6 @@ KSM_ATTR_RO(full_scans);
#ifdef CONFIG_SELECTIVE_KSM
static struct kobject *ksm_base_kobj;
-
-struct partition_kobj {
- struct kobject *kobj;
- struct list_head list;
-};
-
-static LIST_HEAD(partition_list);
-
#else /* CONFIG_SELECTIVE_KSM */
static ssize_t smart_scan_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
@@ -4055,6 +4104,7 @@ static ssize_t add_partition_store(struct kobject *kobj,
struct partition_kobj *new_partition_kobj;
char partition_name[50];
int err;
+ struct rb_root *tree_root;
mutex_lock(&ksm_thread_mutex);
@@ -4081,6 +4131,13 @@ static ssize_t add_partition_store(struct kobject *kobj,
goto unlock;
}
+ tree_root = kcalloc(nr_node_ids + nr_node_ids, sizeof(*tree_root), GFP_KERNEL);
+ if (!tree_root) {
+ err = -ENOMEM;
+ goto unlock;
+ }
+ new_partition_kobj->root_stable_tree = tree_root;
+ new_partition_kobj->root_unstable_tree = tree_root + nr_node_ids;
err = sysfs_create_group(new_partition_kobj->kobj, &ksm_attr_group);
if (err) {
pr_err("ksm: register sysfs failed\n");
--
2.49.0.395.g12beb8f557-goog
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