The patch titled
Subject: stackdepot: add stats counters exported via debugfs
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
stackdepot-add-stats-counters-exported-via-debugfs.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/stackdepot-add-stats-counters-exported-via-debugfs.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Marco Elver <elver@xxxxxxxxxx>
Subject: stackdepot: add stats counters exported via debugfs
Date: Thu, 18 Jan 2024 12:01:29 +0100
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@xxxxxxxxxx
Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/stackdepot.c | 53 +++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 53 insertions(+)
--- a/lib/stackdepot.c~stackdepot-add-stats-counters-exported-via-debugfs
+++ a/lib/stackdepot.c
@@ -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
/* 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
*/
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 stac
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(
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);
_
Patches currently in -mm which might be from elver@xxxxxxxxxx are
stackdepot-add-stats-counters-exported-via-debugfs.patch
stackdepot-make-fast-paths-lock-less-again.patch
