Re: [PATCH 3/5] mm/slub: aggregate and print stack traces in debugfs files

[Hyeonggon Yoo <42.hyeyoo@gmail.com>]

On Fri, Feb 25, 2022 at 07:03:16PM +0100, Vlastimil Babka wrote:
> From: Oliver Glitta <glittao@gmail.com>
> 
> Aggregate objects in slub cache by stack trace in addition to caller
> address when producing contents of debugfs files alloc_traces and
> free_traces in debugfs. Also add the stack traces to the debugfs
> output. This makes it much more useful to e.g. debug memory leaks.
>

I think it will be better if subject was something like
"Differentiate by stack and print stack traces in debugfs"?

> Signed-off-by: Oliver Glitta <glittao@gmail.com>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
> ---
>  mm/slub.c | 28 ++++++++++++++++++++++++++--
>  1 file changed, 26 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index 3140f763e819..06599db4faa3 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -5075,6 +5075,7 @@ EXPORT_SYMBOL(validate_slab_cache);
>   */
>  
>  struct location {
> +	depot_stack_handle_t handle;
>  	unsigned long count;
>  	unsigned long addr;
>  	long long sum_time;
> @@ -5127,9 +5128,13 @@ static int add_location(struct loc_track *t, struct kmem_cache *s,
>  {
>  	long start, end, pos;
>  	struct location *l;
> -	unsigned long caddr;
> +	unsigned long caddr, chandle;
>  	unsigned long age = jiffies - track->when;
> +	depot_stack_handle_t handle = 0;
>  
> +#ifdef CONFIG_STACKDEPOT
> +	handle = READ_ONCE(track->handle);
> +#endif
>  	start = -1;
>  	end = t->count;
>  
> @@ -5144,7 +5149,8 @@ static int add_location(struct loc_track *t, struct kmem_cache *s,
>  			break;
>  
>  		caddr = t->loc[pos].addr;
> -		if (track->addr == caddr) {
> +		chandle = t->loc[pos].handle;
> +		if ((track->addr == caddr) && (handle == chandle)) {
>  
>  			l = &t->loc[pos];
>  			l->count++;
> @@ -5169,6 +5175,8 @@ static int add_location(struct loc_track *t, struct kmem_cache *s,
>  
>  		if (track->addr < caddr)
>  			end = pos;
> +		else if (track->addr == caddr && handle < chandle)
> +			end = pos;
>  		else
>  			start = pos;
>  	}
> @@ -5191,6 +5199,7 @@ static int add_location(struct loc_track *t, struct kmem_cache *s,
>  	l->max_time = age;
>  	l->min_pid = track->pid;
>  	l->max_pid = track->pid;
> +	l->handle = handle;
>  	cpumask_clear(to_cpumask(l->cpus));
>  	cpumask_set_cpu(track->cpu, to_cpumask(l->cpus));
>  	nodes_clear(l->nodes);
> @@ -6102,6 +6111,21 @@ static int slab_debugfs_show(struct seq_file *seq, void *v)
>  			seq_printf(seq, " nodes=%*pbl",
>  				 nodemask_pr_args(&l->nodes));
>  
> +#ifdef CONFIG_STACKDEPOT
> +		{
> +			depot_stack_handle_t handle;
> +			unsigned long *entries;
> +			unsigned int nr_entries, j;
> +
> +			handle = READ_ONCE(l->handle);
> +			if (handle) {
> +				nr_entries = stack_depot_fetch(handle, &entries);
> +				seq_puts(seq, "\n");
> +				for (j = 0; j < nr_entries; j++)
> +					seq_printf(seq, "        %pS\n", (void *)entries[j]);
> +			}
> +		}
> +#endif
>  		seq_puts(seq, "\n");
>  	}
>  
> -- 
> 2.35.1
> 

-- 
Thank you, You are awesome!
Hyeonggon :-)