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-rw-r--r--mm/page_owner.c377
1 files changed, 311 insertions, 66 deletions
diff --git a/mm/page_owner.c b/mm/page_owner.c
index 5634e5d890..8eed0f3dc0 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -36,6 +36,15 @@ struct page_owner {
pid_t free_tgid;
};
+struct stack {
+ struct stack_record *stack_record;
+ struct stack *next;
+};
+static struct stack dummy_stack;
+static struct stack failure_stack;
+static struct stack *stack_list;
+static DEFINE_SPINLOCK(stack_list_lock);
+
static bool page_owner_enabled __initdata;
DEFINE_STATIC_KEY_FALSE(page_owner_inited);
@@ -45,6 +54,22 @@ static depot_stack_handle_t early_handle;
static void init_early_allocated_pages(void);
+static inline void set_current_in_page_owner(void)
+{
+ /*
+ * Avoid recursion.
+ *
+ * We might need to allocate more memory from page_owner code, so make
+ * sure to signal it in order to avoid recursion.
+ */
+ current->in_page_owner = 1;
+}
+
+static inline void unset_current_in_page_owner(void)
+{
+ current->in_page_owner = 0;
+}
+
static int __init early_page_owner_param(char *buf)
{
int ret = kstrtobool(buf, &page_owner_enabled);
@@ -93,8 +118,17 @@ static __init void init_page_owner(void)
register_dummy_stack();
register_failure_stack();
register_early_stack();
- static_branch_enable(&page_owner_inited);
init_early_allocated_pages();
+ /* Initialize dummy and failure stacks and link them to stack_list */
+ dummy_stack.stack_record = __stack_depot_get_stack_record(dummy_handle);
+ failure_stack.stack_record = __stack_depot_get_stack_record(failure_handle);
+ if (dummy_stack.stack_record)
+ refcount_set(&dummy_stack.stack_record->count, 1);
+ if (failure_stack.stack_record)
+ refcount_set(&failure_stack.stack_record->count, 1);
+ dummy_stack.next = &failure_stack;
+ stack_list = &dummy_stack;
+ static_branch_enable(&page_owner_inited);
}
struct page_ext_operations page_owner_ops = {
@@ -115,81 +149,177 @@ static noinline depot_stack_handle_t save_stack(gfp_t flags)
depot_stack_handle_t handle;
unsigned int nr_entries;
- /*
- * Avoid recursion.
- *
- * Sometimes page metadata allocation tracking requires more
- * memory to be allocated:
- * - when new stack trace is saved to stack depot
- */
if (current->in_page_owner)
return dummy_handle;
- current->in_page_owner = 1;
+ set_current_in_page_owner();
nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 2);
handle = stack_depot_save(entries, nr_entries, flags);
if (!handle)
handle = failure_handle;
+ unset_current_in_page_owner();
- current->in_page_owner = 0;
return handle;
}
-void __reset_page_owner(struct page *page, unsigned short order)
+static void add_stack_record_to_list(struct stack_record *stack_record,
+ gfp_t gfp_mask)
{
- int i;
- struct page_ext *page_ext;
- depot_stack_handle_t handle;
- struct page_owner *page_owner;
- u64 free_ts_nsec = local_clock();
+ unsigned long flags;
+ struct stack *stack;
+
+ /* Filter gfp_mask the same way stackdepot does, for consistency */
+ gfp_mask &= ~GFP_ZONEMASK;
+ gfp_mask &= (GFP_ATOMIC | GFP_KERNEL | __GFP_NOLOCKDEP);
+ gfp_mask |= __GFP_NOWARN;
+
+ set_current_in_page_owner();
+ stack = kmalloc(sizeof(*stack), gfp_mask);
+ if (!stack) {
+ unset_current_in_page_owner();
+ return;
+ }
+ unset_current_in_page_owner();
- page_ext = page_ext_get(page);
- if (unlikely(!page_ext))
+ stack->stack_record = stack_record;
+ stack->next = NULL;
+
+ spin_lock_irqsave(&stack_list_lock, flags);
+ stack->next = stack_list;
+ /*
+ * This pairs with smp_load_acquire() from function
+ * stack_start(). This guarantees that stack_start()
+ * will see an updated stack_list before starting to
+ * traverse the list.
+ */
+ smp_store_release(&stack_list, stack);
+ spin_unlock_irqrestore(&stack_list_lock, flags);
+}
+
+static void inc_stack_record_count(depot_stack_handle_t handle, gfp_t gfp_mask,
+ int nr_base_pages)
+{
+ struct stack_record *stack_record = __stack_depot_get_stack_record(handle);
+
+ if (!stack_record)
return;
- handle = save_stack(GFP_NOWAIT | __GFP_NOWARN);
- for (i = 0; i < (1 << order); i++) {
- __clear_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags);
- page_owner = get_page_owner(page_ext);
- page_owner->free_handle = handle;
- page_owner->free_ts_nsec = free_ts_nsec;
- page_owner->free_pid = current->pid;
- page_owner->free_tgid = current->tgid;
- page_ext = page_ext_next(page_ext);
+ /*
+ * New stack_record's that do not use STACK_DEPOT_FLAG_GET start
+ * with REFCOUNT_SATURATED to catch spurious increments of their
+ * refcount.
+ * Since we do not use STACK_DEPOT_FLAG_GET API, let us
+ * set a refcount of 1 ourselves.
+ */
+ if (refcount_read(&stack_record->count) == REFCOUNT_SATURATED) {
+ int old = REFCOUNT_SATURATED;
+
+ if (atomic_try_cmpxchg_relaxed(&stack_record->count.refs, &old, 1))
+ /* Add the new stack_record to our list */
+ add_stack_record_to_list(stack_record, gfp_mask);
}
- page_ext_put(page_ext);
+ refcount_add(nr_base_pages, &stack_record->count);
}
-static inline void __set_page_owner_handle(struct page_ext *page_ext,
- depot_stack_handle_t handle,
- unsigned short order, gfp_t gfp_mask)
+static void dec_stack_record_count(depot_stack_handle_t handle,
+ int nr_base_pages)
+{
+ struct stack_record *stack_record = __stack_depot_get_stack_record(handle);
+
+ if (!stack_record)
+ return;
+
+ if (refcount_sub_and_test(nr_base_pages, &stack_record->count))
+ pr_warn("%s: refcount went to 0 for %u handle\n", __func__,
+ handle);
+}
+
+static inline void __update_page_owner_handle(struct page_ext *page_ext,
+ depot_stack_handle_t handle,
+ unsigned short order,
+ gfp_t gfp_mask,
+ short last_migrate_reason, u64 ts_nsec,
+ pid_t pid, pid_t tgid, char *comm)
{
- struct page_owner *page_owner;
int i;
- u64 ts_nsec = local_clock();
+ struct page_owner *page_owner;
for (i = 0; i < (1 << order); i++) {
page_owner = get_page_owner(page_ext);
page_owner->handle = handle;
page_owner->order = order;
page_owner->gfp_mask = gfp_mask;
- page_owner->last_migrate_reason = -1;
- page_owner->pid = current->pid;
- page_owner->tgid = current->tgid;
+ page_owner->last_migrate_reason = last_migrate_reason;
+ page_owner->pid = pid;
+ page_owner->tgid = tgid;
page_owner->ts_nsec = ts_nsec;
- strscpy(page_owner->comm, current->comm,
+ strscpy(page_owner->comm, comm,
sizeof(page_owner->comm));
__set_bit(PAGE_EXT_OWNER, &page_ext->flags);
__set_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags);
+ page_ext = page_ext_next(page_ext);
+ }
+}
+
+static inline void __update_page_owner_free_handle(struct page_ext *page_ext,
+ depot_stack_handle_t handle,
+ unsigned short order,
+ pid_t pid, pid_t tgid,
+ u64 free_ts_nsec)
+{
+ int i;
+ struct page_owner *page_owner;
+ for (i = 0; i < (1 << order); i++) {
+ page_owner = get_page_owner(page_ext);
+ /* Only __reset_page_owner() wants to clear the bit */
+ if (handle) {
+ __clear_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags);
+ page_owner->free_handle = handle;
+ }
+ page_owner->free_ts_nsec = free_ts_nsec;
+ page_owner->free_pid = current->pid;
+ page_owner->free_tgid = current->tgid;
page_ext = page_ext_next(page_ext);
}
}
+void __reset_page_owner(struct page *page, unsigned short order)
+{
+ struct page_ext *page_ext;
+ depot_stack_handle_t handle;
+ depot_stack_handle_t alloc_handle;
+ struct page_owner *page_owner;
+ u64 free_ts_nsec = local_clock();
+
+ page_ext = page_ext_get(page);
+ if (unlikely(!page_ext))
+ return;
+
+ page_owner = get_page_owner(page_ext);
+ alloc_handle = page_owner->handle;
+
+ handle = save_stack(GFP_NOWAIT | __GFP_NOWARN);
+ __update_page_owner_free_handle(page_ext, handle, order, current->pid,
+ current->tgid, free_ts_nsec);
+ page_ext_put(page_ext);
+
+ if (alloc_handle != early_handle)
+ /*
+ * early_handle is being set as a handle for all those
+ * early allocated pages. See init_pages_in_zone().
+ * Since their refcount is not being incremented because
+ * the machinery is not ready yet, we cannot decrement
+ * their refcount either.
+ */
+ dec_stack_record_count(alloc_handle, 1 << order);
+}
+
noinline void __set_page_owner(struct page *page, unsigned short order,
gfp_t gfp_mask)
{
struct page_ext *page_ext;
+ u64 ts_nsec = local_clock();
depot_stack_handle_t handle;
handle = save_stack(gfp_mask);
@@ -197,8 +327,11 @@ noinline void __set_page_owner(struct page *page, unsigned short order,
page_ext = page_ext_get(page);
if (unlikely(!page_ext))
return;
- __set_page_owner_handle(page_ext, handle, order, gfp_mask);
+ __update_page_owner_handle(page_ext, handle, order, gfp_mask, -1,
+ ts_nsec, current->pid, current->tgid,
+ current->comm);
page_ext_put(page_ext);
+ inc_stack_record_count(handle, gfp_mask, 1 << order);
}
void __set_page_owner_migrate_reason(struct page *page, int reason)
@@ -214,7 +347,7 @@ void __set_page_owner_migrate_reason(struct page *page, int reason)
page_ext_put(page_ext);
}
-void __split_page_owner(struct page *page, unsigned int nr)
+void __split_page_owner(struct page *page, int old_order, int new_order)
{
int i;
struct page_ext *page_ext = page_ext_get(page);
@@ -223,9 +356,9 @@ void __split_page_owner(struct page *page, unsigned int nr)
if (unlikely(!page_ext))
return;
- for (i = 0; i < nr; i++) {
+ for (i = 0; i < (1 << old_order); i++) {
page_owner = get_page_owner(page_ext);
- page_owner->order = 0;
+ page_owner->order = new_order;
page_ext = page_ext_next(page_ext);
}
page_ext_put(page_ext);
@@ -233,9 +366,12 @@ void __split_page_owner(struct page *page, unsigned int nr)
void __folio_copy_owner(struct folio *newfolio, struct folio *old)
{
+ int i;
struct page_ext *old_ext;
struct page_ext *new_ext;
- struct page_owner *old_page_owner, *new_page_owner;
+ struct page_owner *old_page_owner;
+ struct page_owner *new_page_owner;
+ depot_stack_handle_t migrate_handle;
old_ext = page_ext_get(&old->page);
if (unlikely(!old_ext))
@@ -249,30 +385,32 @@ void __folio_copy_owner(struct folio *newfolio, struct folio *old)
old_page_owner = get_page_owner(old_ext);
new_page_owner = get_page_owner(new_ext);
- new_page_owner->order = old_page_owner->order;
- new_page_owner->gfp_mask = old_page_owner->gfp_mask;
- new_page_owner->last_migrate_reason =
- old_page_owner->last_migrate_reason;
- new_page_owner->handle = old_page_owner->handle;
- new_page_owner->pid = old_page_owner->pid;
- new_page_owner->tgid = old_page_owner->tgid;
- new_page_owner->free_pid = old_page_owner->free_pid;
- new_page_owner->free_tgid = old_page_owner->free_tgid;
- new_page_owner->ts_nsec = old_page_owner->ts_nsec;
- new_page_owner->free_ts_nsec = old_page_owner->ts_nsec;
- strcpy(new_page_owner->comm, old_page_owner->comm);
-
+ migrate_handle = new_page_owner->handle;
+ __update_page_owner_handle(new_ext, old_page_owner->handle,
+ old_page_owner->order, old_page_owner->gfp_mask,
+ old_page_owner->last_migrate_reason,
+ old_page_owner->ts_nsec, old_page_owner->pid,
+ old_page_owner->tgid, old_page_owner->comm);
/*
- * We don't clear the bit on the old folio as it's going to be freed
- * after migration. Until then, the info can be useful in case of
- * a bug, and the overall stats will be off a bit only temporarily.
- * Also, migrate_misplaced_transhuge_page() can still fail the
- * migration and then we want the old folio to retain the info. But
- * in that case we also don't need to explicitly clear the info from
- * the new page, which will be freed.
+ * Do not proactively clear PAGE_EXT_OWNER{_ALLOCATED} bits as the folio
+ * will be freed after migration. Keep them until then as they may be
+ * useful.
*/
- __set_bit(PAGE_EXT_OWNER, &new_ext->flags);
- __set_bit(PAGE_EXT_OWNER_ALLOCATED, &new_ext->flags);
+ __update_page_owner_free_handle(new_ext, 0, old_page_owner->order,
+ old_page_owner->free_pid,
+ old_page_owner->free_tgid,
+ old_page_owner->free_ts_nsec);
+ /*
+ * We linked the original stack to the new folio, we need to do the same
+ * for the new one and the old folio otherwise there will be an imbalance
+ * when subtracting those pages from the stack.
+ */
+ for (i = 0; i < (1 << new_page_owner->order); i++) {
+ old_page_owner->handle = migrate_handle;
+ old_ext = page_ext_next(old_ext);
+ old_page_owner = get_page_owner(old_ext);
+ }
+
page_ext_put(new_ext);
page_ext_put(old_ext);
}
@@ -680,8 +818,9 @@ static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
goto ext_put_continue;
/* Found early allocated page */
- __set_page_owner_handle(page_ext, early_handle,
- 0, 0);
+ __update_page_owner_handle(page_ext, early_handle, 0, 0,
+ -1, local_clock(), current->pid,
+ current->tgid, current->comm);
count++;
ext_put_continue:
page_ext_put(page_ext);
@@ -719,8 +858,109 @@ static const struct file_operations proc_page_owner_operations = {
.llseek = lseek_page_owner,
};
+static void *stack_start(struct seq_file *m, loff_t *ppos)
+{
+ struct stack *stack;
+
+ if (*ppos == -1UL)
+ return NULL;
+
+ if (!*ppos) {
+ /*
+ * This pairs with smp_store_release() from function
+ * add_stack_record_to_list(), so we get a consistent
+ * value of stack_list.
+ */
+ stack = smp_load_acquire(&stack_list);
+ m->private = stack;
+ } else {
+ stack = m->private;
+ }
+
+ return stack;
+}
+
+static void *stack_next(struct seq_file *m, void *v, loff_t *ppos)
+{
+ struct stack *stack = v;
+
+ stack = stack->next;
+ *ppos = stack ? *ppos + 1 : -1UL;
+ m->private = stack;
+
+ return stack;
+}
+
+static unsigned long page_owner_pages_threshold;
+
+static int stack_print(struct seq_file *m, void *v)
+{
+ int i, nr_base_pages;
+ struct stack *stack = v;
+ unsigned long *entries;
+ unsigned long nr_entries;
+ struct stack_record *stack_record = stack->stack_record;
+
+ if (!stack->stack_record)
+ return 0;
+
+ nr_entries = stack_record->size;
+ entries = stack_record->entries;
+ nr_base_pages = refcount_read(&stack_record->count) - 1;
+
+ if (nr_base_pages < 1 || nr_base_pages < page_owner_pages_threshold)
+ return 0;
+
+ for (i = 0; i < nr_entries; i++)
+ seq_printf(m, " %pS\n", (void *)entries[i]);
+ seq_printf(m, "nr_base_pages: %d\n\n", nr_base_pages);
+
+ return 0;
+}
+
+static void stack_stop(struct seq_file *m, void *v)
+{
+}
+
+static const struct seq_operations page_owner_stack_op = {
+ .start = stack_start,
+ .next = stack_next,
+ .stop = stack_stop,
+ .show = stack_print
+};
+
+static int page_owner_stack_open(struct inode *inode, struct file *file)
+{
+ return seq_open_private(file, &page_owner_stack_op, 0);
+}
+
+static const struct file_operations page_owner_stack_operations = {
+ .open = page_owner_stack_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_release,
+};
+
+static int page_owner_threshold_get(void *data, u64 *val)
+{
+ *val = READ_ONCE(page_owner_pages_threshold);
+ return 0;
+}
+
+static int page_owner_threshold_set(void *data, u64 val)
+{
+ WRITE_ONCE(page_owner_pages_threshold, val);
+ return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(proc_page_owner_threshold, &page_owner_threshold_get,
+ &page_owner_threshold_set, "%llu");
+
+
static int __init pageowner_init(void)
{
+ struct dentry *dir;
+
if (!static_branch_unlikely(&page_owner_inited)) {
pr_info("page_owner is disabled\n");
return 0;
@@ -728,6 +968,11 @@ static int __init pageowner_init(void)
debugfs_create_file("page_owner", 0400, NULL, NULL,
&proc_page_owner_operations);
+ dir = debugfs_create_dir("page_owner_stacks", NULL);
+ debugfs_create_file("show_stacks", 0400, dir, NULL,
+ &page_owner_stack_operations);
+ debugfs_create_file("count_threshold", 0600, dir, NULL,
+ &proc_page_owner_threshold);
return 0;
}