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mm,page_owner: display all stacks and their count

Browse source 
This patch adds a new directory called 'page_owner_stacks' under
/sys/kernel/debug/, with a file called 'show_stacks' in it.  Reading from
that file will show all stacks that were added by page_owner followed by
their counting, giving us a clear overview of stack <-> count
relationship.

E.g:

  prep_new_page+0xa9/0x120
  get_page_from_freelist+0x801/0x2210
  __alloc_pages+0x18b/0x350
  alloc_pages_mpol+0x91/0x1f0
  folio_alloc+0x14/0x50
  filemap_alloc_folio+0xb2/0x100
  __filemap_get_folio+0x14a/0x490
  ext4_write_begin+0xbd/0x4b0 [ext4]
  generic_perform_write+0xc1/0x1e0
  ext4_buffered_write_iter+0x68/0xe0 [ext4]
  ext4_file_write_iter+0x70/0x740 [ext4]
  vfs_write+0x33d/0x420
  ksys_write+0xa5/0xe0
  do_syscall_64+0x80/0x160
  entry_SYSCALL_64_after_hwframe+0x6e/0x76
 stack_count: 4578

The seq stack_{start,next} functions will iterate through the list
stack_list in order to print all stacks.

Link: https://lkml.kernel.org/r/20240215215907.20121-6-osalvador@suse.de
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Marco Elver <elver@google.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Oscar Salvador 2024-02-15 22:59:05 +01:00 committed by Andrew Morton
parent 217b2119b9
commit 765973a098
1 changed files with 92 additions and 1 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

93
mm/page_owner.c
View file

@ -171,7 +171,13 @@ static void add_stack_record_to_list(struct stack_record *stack_record,
spin_lock_irqsave(&stack_list_lock, flags);
stack->next = stack_list;
stack_list = stack;
/*
* 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);
}
@ -805,8 +811,90 @@ 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);
} else {
stack = m->private;
stack = stack->next;
}
m->private = stack;
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 int stack_print(struct seq_file *m, void *v)
{
int i, stack_count;
struct stack *stack = v;
unsigned long *entries;
unsigned long nr_entries;
struct stack_record *stack_record = stack->stack_record;
nr_entries = stack_record->size;
entries = stack_record->entries;
stack_count = refcount_read(&stack_record->count) - 1;
if (!nr_entries || nr_entries < 0 || stack_count < 1)
return 0;
for (i = 0; i < nr_entries; i++)
seq_printf(m, " %pS\n", (void *)entries[i]);
seq_printf(m, "stack_count: %d\n\n", stack_count);
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 __init pageowner_init(void)
{
struct dentry *dir;
if (!static_branch_unlikely(&page_owner_inited)) {
pr_info("page_owner is disabled\n");
return 0;
@ -814,6 +902,9 @@ 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);
return 0;
}