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stackdepot: add stats counters exported via debugfs

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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: Marco Elver <elver@google.com>
Reviewed-by: Andrey 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: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Marco Elver 2024-01-18 12:01:29 +01:00 committed by Andrew Morton
parent f6564fce25
commit c2a292545c
1 changed files with 53 additions and 0 deletions
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53
lib/stackdepot.c
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@ -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);