Commit c2a29254 authored by Marco Elver's avatar Marco Elver Committed by Andrew Morton
Browse files

stackdepot: add stats counters exported via debugfs 

Add a few basic stats counters for stack depot that can be used to derive
if stack depot is working as intended.  This is a snapshot of the new
stats after booting a system with a KASAN-enabled kernel:

 $ cat /sys/kernel/debug/stackdepot/stats
 pools: 838
 allocations: 29861
 frees: 6561
 in_use: 23300
 freelist_size: 1840

Generally, "pools" should be well below the max; once the system is
booted, "in_use" should remain relatively steady.

Link: https://lkml.kernel.org/r/20240118110216.2539519-1-elver@google.com


Signed-off-by: default avatarMarco Elver <elver@google.com>
Reviewed-by: default avatarAndrey Konovalov <andreyknvl@gmail.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Alexander Potapenko <glider@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent f6564fce

lib/stackdepot.c

+53 −0
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ 


#define pr_fmt(fmt) "stackdepot: " fmt



#include <linux/debugfs.h>

#include <linux/gfp.h>

#include <linux/jhash.h>

#include <linux/kernel.h>
@@ -115,6 +116,23 @@ static bool new_pool_required = true; 
/* Lock that protects the variables above. */

static DEFINE_RWLOCK(pool_rwlock);



/* Statistics counters for debugfs. */

enum depot_counter_id {

	DEPOT_COUNTER_ALLOCS,

	DEPOT_COUNTER_FREES,

	DEPOT_COUNTER_INUSE,

	DEPOT_COUNTER_FREELIST_SIZE,

	DEPOT_COUNTER_COUNT,

};

static long counters[DEPOT_COUNTER_COUNT];

static const char *const counter_names[] = {

	[DEPOT_COUNTER_ALLOCS]		= "allocations",

	[DEPOT_COUNTER_FREES]		= "frees",

	[DEPOT_COUNTER_INUSE]		= "in_use",

	[DEPOT_COUNTER_FREELIST_SIZE]	= "freelist_size",

};

static_assert(ARRAY_SIZE(counter_names) == DEPOT_COUNTER_COUNT);



static int __init disable_stack_depot(char *str)

{

	return kstrtobool(str, &stack_depot_disabled);
@@ -277,6 +295,7 @@ static void depot_init_pool(void *pool) 
		stack->handle.extra = 0;



		list_add(&stack->list, &free_stacks);

		counters[DEPOT_COUNTER_FREELIST_SIZE]++;

	}



	/* Save reference to the pool to be used by depot_fetch_stack(). */
@@ -376,6 +395,7 @@ depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc) 
	/* Get and unlink the first entry from the freelist. */

	stack = list_first_entry(&free_stacks, struct stack_record, list);

	list_del(&stack->list);

	counters[DEPOT_COUNTER_FREELIST_SIZE]--;



	/* Limit number of saved frames to CONFIG_STACKDEPOT_MAX_FRAMES. */

	if (size > CONFIG_STACKDEPOT_MAX_FRAMES)
@@ -394,6 +414,8 @@ depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc) 
	 */

	kmsan_unpoison_memory(stack, DEPOT_STACK_RECORD_SIZE);



	counters[DEPOT_COUNTER_ALLOCS]++;

	counters[DEPOT_COUNTER_INUSE]++;

	return stack;

}
@@ -426,6 +448,10 @@ static void depot_free_stack(struct stack_record *stack) 
	lockdep_assert_held_write(&pool_rwlock);



	list_add(&stack->list, &free_stacks);



	counters[DEPOT_COUNTER_FREELIST_SIZE]++;

	counters[DEPOT_COUNTER_FREES]++;

	counters[DEPOT_COUNTER_INUSE]--;

}



/* Calculates the hash for a stack. */
@@ -690,3 +716,30 @@ unsigned int stack_depot_get_extra_bits(depot_stack_handle_t handle) 
	return parts.extra;

}

EXPORT_SYMBOL(stack_depot_get_extra_bits);



static int stats_show(struct seq_file *seq, void *v)

{

	/*

	 * data race ok: These are just statistics counters, and approximate

	 * statistics are ok for debugging.

	 */

	seq_printf(seq, "pools: %d\n", data_race(pools_num));

	for (int i = 0; i < DEPOT_COUNTER_COUNT; i++)

		seq_printf(seq, "%s: %ld\n", counter_names[i], data_race(counters[i]));



	return 0;

}

DEFINE_SHOW_ATTRIBUTE(stats);



static int depot_debugfs_init(void)

{

	struct dentry *dir;



	if (stack_depot_disabled)

		return 0;



	dir = debugfs_create_dir("stackdepot", NULL);

	debugfs_create_file("stats", 0444, dir, NULL, &stats_fops);

	return 0;

}

late_initcall(depot_debugfs_init);