linux-kernel - Re: [PATCH v9 6/7] mm,page_owner: Filter out stacks by a threshold

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Message-ID: <bb7112a8-df8a-4df8-a8db-0cb4761720dd@suse.cz>
Date: Thu, 15 Feb 2024 12:12:56 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Oscar Salvador <osalvador@...e.de>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 Michal Hocko <mhocko@...e.com>, Marco Elver <elver@...gle.com>,
 Andrey Konovalov <andreyknvl@...il.com>,
 Alexander Potapenko <glider@...gle.com>
Subject: Re: [PATCH v9 6/7] mm,page_owner: Filter out stacks by a threshold

On 2/14/24 18:01, 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@...e.de>

Reviewed-by: Vlastimil Babka <vbabka@...e.cz>
..

> ---
>  mm/page_owner.c | 29 +++++++++++++++++++++++++----
>  1 file changed, 25 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/page_owner.c b/mm/page_owner.c
> index 5258a417f4d1..9b975f59b773 100644
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -846,9 +846,11 @@ 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;
> +	int i, stack_count;
>  	struct stack *stack = v;
>  	unsigned long *entries;
>  	unsigned long nr_entries;
> @@ -856,14 +858,15 @@ static int stack_print(struct seq_file *m, void *v)
>  
>  	nr_entries = stack_record->size;
>  	entries = stack_record->entries;
> +	stack_count = refcount_read(&stack_record->count);

Again "- 1" here.

> -	if (!nr_entries || nr_entries < 0 ||
> -	    refcount_read(&stack_record->count) < 2)
> +	if (!nr_entries || nr_entries < 0 || stack_count < 2 ||
> +	    stack_count < page_owner_stack_threshold)

Which will also correct the comparison.

>  		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", refcount_read(&stack_record->count));
> +	seq_printf(m, "stack_count: %d\n\n", stack_count);

And no - 1 needed here then.