Hi
On 2024/2/16 5:59, Oscar Salvador wrote:
> We want to be able to filter out the stacks based on a threshold we can
> can tune.
> By writing to 'count_threshold' file, we can adjust the threshold value.
>
> Signed-off-by: Oscar Salvador <osalvador@suse.de>
> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
> ---
> mm/page_owner.c | 23 ++++++++++++++++++++++-
> 1 file changed, 22 insertions(+), 1 deletion(-)
>
> diff --git a/mm/page_owner.c b/mm/page_owner.c
> index e99fbf822dd6..e56c1e92eccf 100644
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -846,6 +846,8 @@ static void *stack_next(struct seq_file *m, void *v, loff_t *ppos)
> return stack;
> }
>
> +static unsigned long page_owner_stack_threshold;
> +
> static int stack_print(struct seq_file *m, void *v)
> {
> int i, stack_count;
> @@ -858,7 +860,8 @@ static int stack_print(struct seq_file *m, void *v)
> entries = stack_record->entries;
> stack_count = refcount_read(&stack_record->count) - 1;
>
> - if (!nr_entries || nr_entries < 0 || stack_count < 1)
> + if (!nr_entries || nr_entries < 0 || stack_count < 1 ||
> + stack_count < page_owner_stack_threshold)
> return 0;
>
> for (i = 0; i < nr_entries; i++)
> @@ -891,6 +894,22 @@ static const struct file_operations page_owner_stack_operations = {
> .release = seq_release,
> };
>
> +static int page_owner_threshold_get(void *data, u64 *val)
> +{
> + *val = READ_ONCE(page_owner_stack_threshold);
> + return 0;
> +}
> +
> +static int page_owner_threshold_set(void *data, u64 val)
> +{
> + WRITE_ONCE(page_owner_stack_threshold, val);
> + return 0;
> +}
no need READ/WRITE_ONCE between get/set, since simple_attr_read/write()
with a mutex, but set and stack_print could date race
> +
> +DEFINE_SIMPLE_ATTRIBUTE(proc_page_owner_threshold, &page_owner_threshold_get,
> + &page_owner_threshold_set, "%llu");
%llu\n"
In addition, since we have a stack_list, could we add a new feature to
dump stack info with threshold with OOM notifier, because many users
directly call alloc_page family, which makes it too difficult to debug
during OOM.
Thanks
> +
> +
> static int __init pageowner_init(void)
> {
> struct dentry *dir;
> @@ -905,6 +924,8 @@ static int __init pageowner_init(void)
> 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;
> }