Re: [patch 22/25] debugobjects: Move pool statistics into global_pool struct

[Leizhen (ThunderTown)]

On 2024/10/8 0:50, Thomas Gleixner wrote:
> Keep it along with the pool as that's a hot cache line anyway and it makes
> the code more comprehensible.

Reviewed-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>

> 
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> ---
>  lib/debugobjects.c |   85 +++++++++++++++++++++++++++++++----------------------
>  1 file changed, 51 insertions(+), 34 deletions(-)
> 
> --- a/lib/debugobjects.c
> +++ b/lib/debugobjects.c
> @@ -47,11 +47,18 @@ struct debug_bucket {
>  	raw_spinlock_t		lock;
>  };
>  
> +struct pool_stats {
> +	unsigned int		cur_used;
> +	unsigned int		max_used;
> +	unsigned int		min_fill;
> +};
> +
>  struct obj_pool {
>  	struct hlist_head	objects;
>  	unsigned int		cnt;
>  	unsigned int		min_cnt;
>  	unsigned int		max_cnt;
> +	struct pool_stats	stats;
>  } ____cacheline_aligned;
>  
>  
> @@ -66,8 +73,11 @@ static struct debug_obj		obj_static_pool
>  static DEFINE_RAW_SPINLOCK(pool_lock);
>  
>  static struct obj_pool pool_global = {
> -	.min_cnt	= ODEBUG_POOL_MIN_LEVEL,
> -	.max_cnt	= ODEBUG_POOL_SIZE,
> +	.min_cnt		= ODEBUG_POOL_MIN_LEVEL,
> +	.max_cnt		= ODEBUG_POOL_SIZE,
> +	.stats			= {
> +		.min_fill	= ODEBUG_POOL_SIZE,
> +	},
>  };
>  
>  static struct obj_pool pool_to_free = {
> @@ -76,16 +86,6 @@ static struct obj_pool pool_to_free = {
>  
>  static HLIST_HEAD(pool_boot);
>  
> -/*
> - * Because of the presence of percpu free pools, obj_pool_free will
> - * under-count those in the percpu free pools. Similarly, obj_pool_used
> - * will over-count those in the percpu free pools. Adjustments will be
> - * made at debug_stats_show(). Both obj_pool_min_free and obj_pool_max_used
> - * can be off.
> - */
> -static int __data_racy		obj_pool_min_free = ODEBUG_POOL_SIZE;
> -static int			obj_pool_used;
> -static int __data_racy		obj_pool_max_used;
>  static bool			obj_freeing;
>  
>  static int __data_racy			debug_objects_maxchain __read_mostly;
> @@ -231,6 +231,19 @@ static struct debug_obj *__alloc_object(
>  	return obj;
>  }
>  
> +static void pcpu_refill_stats(void)
> +{
> +	struct pool_stats *stats = &pool_global.stats;
> +
> +	WRITE_ONCE(stats->cur_used, stats->cur_used + ODEBUG_BATCH_SIZE);
> +
> +	if (stats->cur_used > stats->max_used)
> +		stats->max_used = stats->cur_used;
> +
> +	if (pool_global.cnt < stats->min_fill)
> +		stats->min_fill = pool_global.cnt;
> +}
> +
>  static struct debug_obj *pcpu_alloc(void)
>  {
>  	struct obj_pool *pcp = this_cpu_ptr(&pool_pcpu);
> @@ -250,13 +263,7 @@ static struct debug_obj *pcpu_alloc(void
>  			if (!pool_move_batch(pcp, &pool_global))
>  				return NULL;
>  		}
> -		obj_pool_used += ODEBUG_BATCH_SIZE;
> -
> -		if (obj_pool_used > obj_pool_max_used)
> -			obj_pool_max_used = obj_pool_used;
> -
> -		if (pool_global.cnt < obj_pool_min_free)
> -			obj_pool_min_free = pool_global.cnt;
> +		pcpu_refill_stats();
>  	}
>  }
>  
> @@ -285,7 +292,7 @@ static void pcpu_free(struct debug_obj *
>  	/* Try to fit the batch into the pool_global first */
>  	if (!pool_move_batch(&pool_global, pcp))
>  		pool_move_batch(&pool_to_free, pcp);
> -	obj_pool_used -= ODEBUG_BATCH_SIZE;
> +	WRITE_ONCE(pool_global.stats.cur_used, pool_global.stats.cur_used - ODEBUG_BATCH_SIZE);
>  }
>  
>  static void free_object_list(struct hlist_head *head)
> @@ -1074,23 +1081,33 @@ void debug_check_no_obj_freed(const void
>  
>  static int debug_stats_show(struct seq_file *m, void *v)
>  {
> -	int cpu, obj_percpu_free = 0;
> +	unsigned int cpu, pool_used, pcp_free = 0;
>  
> +	/*
> +	 * pool_global.stats.cur_used is the number of batches currently
> +	 * handed out to per CPU pools. Convert it to number of objects
> +	 * and subtract the number of free objects in the per CPU pools.
> +	 * As this is lockless the number is an estimate.
> +	 */
>  	for_each_possible_cpu(cpu)
> -		obj_percpu_free += per_cpu(pool_pcpu.cnt, cpu);
> +		pcp_free += per_cpu(pool_pcpu.cnt, cpu);
>  
> -	seq_printf(m, "max_chain     :%d\n", debug_objects_maxchain);
> -	seq_printf(m, "max_checked   :%d\n", debug_objects_maxchecked);
> -	seq_printf(m, "warnings      :%d\n", debug_objects_warnings);
> -	seq_printf(m, "fixups        :%d\n", debug_objects_fixups);
> -	seq_printf(m, "pool_free     :%d\n", pool_count(&pool_global) + obj_percpu_free);
> -	seq_printf(m, "pool_pcp_free :%d\n", obj_percpu_free);
> -	seq_printf(m, "pool_min_free :%d\n", obj_pool_min_free);
> -	seq_printf(m, "pool_used     :%d\n", obj_pool_used - obj_percpu_free);
> -	seq_printf(m, "pool_max_used :%d\n", obj_pool_max_used);
> -	seq_printf(m, "on_free_list  :%d\n", pool_count(&pool_to_free));
> -	seq_printf(m, "objs_allocated:%d\n", debug_objects_allocated);
> -	seq_printf(m, "objs_freed    :%d\n", debug_objects_freed);
> +	pool_used = data_race(pool_global.stats.cur_used);
> +	pcp_free = min(pool_used, pcp_free);
> +	pool_used -= pcp_free;
> +
> +	seq_printf(m, "max_chain     : %d\n", debug_objects_maxchain);
> +	seq_printf(m, "max_checked   : %d\n", debug_objects_maxchecked);
> +	seq_printf(m, "warnings      : %d\n", debug_objects_warnings);
> +	seq_printf(m, "fixups        : %d\n", debug_objects_fixups);
> +	seq_printf(m, "pool_free     : %u\n", pool_count(&pool_global) + pcp_free);
> +	seq_printf(m, "pool_pcp_free : %u\n", pcp_free);
> +	seq_printf(m, "pool_min_free : %u\n", data_race(pool_global.stats.min_fill));
> +	seq_printf(m, "pool_used     : %u\n", pool_used);
> +	seq_printf(m, "pool_max_used : %u\n", data_race(pool_global.stats.max_used));
> +	seq_printf(m, "on_free_list  : %u\n", pool_count(&pool_to_free));
> +	seq_printf(m, "objs_allocated: %d\n", debug_objects_allocated);
> +	seq_printf(m, "objs_freed    : %d\n", debug_objects_freed);
>  	return 0;
>  }
>  DEFINE_SHOW_ATTRIBUTE(debug_stats);
> 
> .
> 

-- 
Regards,
  Zhen Lei