From c2a292545cd43dcab86d5290ed95b006f1cefe90 Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Thu, 18 Jan 2024 12:01:29 +0100 Subject: 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: Marco Elver Reviewed-by: Andrey Konovalov Cc: Andi Kleen Cc: Dmitry Vyukov Cc: Vlastimil Babka Cc: Alexander Potapenko Signed-off-by: Andrew Morton --- lib/stackdepot.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 53 insertions(+) diff --git a/lib/stackdepot.c b/lib/stackdepot.c index a0be5d05c7f0..80a8ca24ccc8 100644 --- a/lib/stackdepot.c +++ b/lib/stackdepot.c @@ -14,6 +14,7 @@ #define pr_fmt(fmt) "stackdepot: " fmt +#include #include #include #include @@ -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); -- cgit