On Mon, Sep 05, 2022 at 05:10AM +0200, Oscar Salvador wrote:
[...]
> +int stack_depot_print_stacks_threshold(char *buf, size_t size, loff_t *pos)
Can you add kernel-doc comment what this does (and also update
accordingly in 3/3 when you add 'threshold').
>From what I see it prints *all* stacks that have a non-zero count.
Correct?
If so, should this be called stack_depot_print_all_count() (having
stack(s) in the name twice doesn't make it more obvious what it does)?
Then in the follow-up patch you add the 'threshold' arg.
> +{
> + int i = *pos, ret = 0;
> + struct stack_record **stacks, *stack;
> + static struct stack_record *last = NULL;
> + unsigned long stack_table_entries = stack_hash_mask + 1;
> +
> + /* Continue from the last stack if we have one */
> + if (last) {
> + stack = last->next;
This is dead code?
> + } else {
> +new_table:
> + stacks = &stack_table[i];
> + stack = (struct stack_record *)stacks;
> + }
> +
> + for (; stack; stack = stack->next) {
> + if (!stack->size || stack->size < 0 ||
> + stack->size > size || stack->handle.valid != 1 ||
> + refcount_read(&stack->count) < 1)
> + continue;
> +
> + ret += stack_trace_snprint(buf, size, stack->entries, stack->size, 0);
> + ret += scnprintf(buf + ret, size - ret, "stack count: %d\n\n",
> + refcount_read(&stack->count));
> + last = stack;
> + return ret;
> + }
> +
> + i++;
> + *pos = i;
> + last = NULL;
> +
> + /* Keep looking all tables for valid stacks */
> + if (i < stack_table_entries)
> + goto new_table;
> +
> + return 0;
> +}
Either I'm missing something really obvious, but I was able to simplify
the above function to just this (untested!):
int stack_depot_print_stacks_threshold(char *buf, size_t size, loff_t *pos)
{
const unsigned long stack_table_entries = stack_hash_mask + 1;
/* Iterate over all tables for valid stacks. */
for (; *pos < stack_table_entries; (*pos)++) {
for (struct stack_record *stack = stack_table[*pos]; stack; stack = stack->next) {
if (!stack->size || stack->size < 0 || stack->size > size ||
stack->handle.valid != 1 || refcount_read(&stack->count) < 1)
continue;
return stack_trace_snprint(buf, size, stack->entries, stack->size, 0) +
scnprintf(buf + ret, size - ret, "stack count: %d\n\n",
refcount_read(&stack->count));
}
}
return 0;
}
> diff --git a/mm/page_owner.c b/mm/page_owner.c
> index 8730f377fa91..d88e6b4aefa0 100644
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -664,6 +664,29 @@ static void init_early_allocated_pages(void)
> init_zones_in_node(pgdat);
> }
>
> +static ssize_t read_page_owner_stacks(struct file *file, char __user *buf,
> + size_t count, loff_t *pos)
> +{
> + char *kbuf;
> + int ret = 0;
> +
> + count = min_t(size_t, count, PAGE_SIZE);
> + kbuf = kmalloc(count, GFP_KERNEL);
> + if (!kbuf)
> + return -ENOMEM;
> +
> + ret += stack_depot_print_stacks_threshold(kbuf, count, pos);
If I understood right, this will print *all* stacks that have non-zero
count, and this isn't related to page_owner per-se. Correct?
This might not be a problem right now, but once there might be more
users that want to count stack usage, you'll end up with page_owner +
other stacks here.
