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Message-ID: <365d6eb6-7a35-a8a3-1942-2a931a6d9f5d@huawei.com>
Date: Thu, 10 Oct 2024 17:50:40 +0800
From: "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
To: Thomas Gleixner <tglx@...utronix.de>, LKML <linux-kernel@...r.kernel.org>
CC: Waiman Long <longman@...hat.com>
Subject: Re: [patch 22/25] debugobjects: Move pool statistics into global_pool
struct
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@...wei.com>
>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
> 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
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