[GIT PULL] debugobjects changes for v4.17

From: Ingo Molnar
Date: Mon Apr 02 2018 - 02:23:27 EST

Linus,

Please pull the latest core-debugobjects-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git core-debugobjects-for-linus

# HEAD: 163cf842f5837334bc69aaf09ad38e11f4573914 debugobjects: Avoid another unused variable warning

Misc improvements:

- add better instrumentation/debugging
- optimize the freeing logic improve performance

Thanks,

Ingo

------------------>
Arnd Bergmann (2):
debugobjects: Fix debug_objects_freed accounting
debugobjects: Avoid another unused variable warning

Yang Shi (4):
debugobjects: Export max loops counter
debugobjects: Add global free list and the counter
debugobjects: Use global free list in free_object()
debugobjects: Use global free list in __debug_check_no_obj_freed()


lib/debugobjects.c | 141 ++++++++++++++++++++++++++++++++++-------------------
1 file changed, 92 insertions(+), 49 deletions(-)

diff --git a/lib/debugobjects.c b/lib/debugobjects.c
index 2f5349c6e81a..994be4805cec 100644
--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -42,14 +42,18 @@ static struct debug_obj obj_static_pool[ODEBUG_POOL_SIZE] __initdata;
static DEFINE_RAW_SPINLOCK(pool_lock);

static HLIST_HEAD(obj_pool);
+static HLIST_HEAD(obj_to_free);

static int obj_pool_min_free = ODEBUG_POOL_SIZE;
static int obj_pool_free = ODEBUG_POOL_SIZE;
static int obj_pool_used;
static int obj_pool_max_used;
+/* The number of objs on the global free list */
+static int obj_nr_tofree;
static struct kmem_cache *obj_cache;

static int debug_objects_maxchain __read_mostly;
+static int __maybe_unused debug_objects_maxchecked __read_mostly;
static int debug_objects_fixups __read_mostly;
static int debug_objects_warnings __read_mostly;
static int debug_objects_enabled __read_mostly
@@ -96,12 +100,32 @@ static const char *obj_states[ODEBUG_STATE_MAX] = {
static void fill_pool(void)
{
gfp_t gfp = GFP_ATOMIC | __GFP_NORETRY | __GFP_NOWARN;
- struct debug_obj *new;
+ struct debug_obj *new, *obj;
unsigned long flags;

if (likely(obj_pool_free >= debug_objects_pool_min_level))
return;

+ /*
+ * Reuse objs from the global free list; they will be reinitialized
+ * when allocating.
+ */
+ while (obj_nr_tofree && (obj_pool_free < obj_pool_min_free)) {
+ raw_spin_lock_irqsave(&pool_lock, flags);
+ /*
+ * Recheck with the lock held as the worker thread might have
+ * won the race and freed the global free list already.
+ */
+ if (obj_nr_tofree) {
+ obj = hlist_entry(obj_to_free.first, typeof(*obj), node);
+ hlist_del(&obj->node);
+ obj_nr_tofree--;
+ hlist_add_head(&obj->node, &obj_pool);
+ obj_pool_free++;
+ }
+ raw_spin_unlock_irqrestore(&pool_lock, flags);
+ }
+
if (unlikely(!obj_cache))
return;

@@ -177,62 +201,76 @@ alloc_object(void *addr, struct debug_bucket *b, struct debug_obj_descr *descr)
* workqueue function to free objects.
*
* To reduce contention on the global pool_lock, the actual freeing of
- * debug objects will be delayed if the pool_lock is busy. We also free
- * the objects in a batch of 4 for each lock/unlock cycle.
+ * debug objects will be delayed if the pool_lock is busy.
*/
-#define ODEBUG_FREE_BATCH 4
-
static void free_obj_work(struct work_struct *work)
{
- struct debug_obj *objs[ODEBUG_FREE_BATCH];
+ struct hlist_node *tmp;
+ struct debug_obj *obj;
unsigned long flags;
- int i;
+ HLIST_HEAD(tofree);

if (!raw_spin_trylock_irqsave(&pool_lock, flags))
return;
- while (obj_pool_free >= debug_objects_pool_size + ODEBUG_FREE_BATCH) {
- for (i = 0; i < ODEBUG_FREE_BATCH; i++) {
- objs[i] = hlist_entry(obj_pool.first,
- typeof(*objs[0]), node);
- hlist_del(&objs[i]->node);
- }

- obj_pool_free -= ODEBUG_FREE_BATCH;
- debug_objects_freed += ODEBUG_FREE_BATCH;
- /*
- * We release pool_lock across kmem_cache_free() to
- * avoid contention on pool_lock.
- */
- raw_spin_unlock_irqrestore(&pool_lock, flags);
- for (i = 0; i < ODEBUG_FREE_BATCH; i++)
- kmem_cache_free(obj_cache, objs[i]);
- if (!raw_spin_trylock_irqsave(&pool_lock, flags))
- return;
+ /*
+ * The objs on the pool list might be allocated before the work is
+ * run, so recheck if pool list it full or not, if not fill pool
+ * list from the global free list
+ */
+ while (obj_nr_tofree && obj_pool_free < debug_objects_pool_size) {
+ obj = hlist_entry(obj_to_free.first, typeof(*obj), node);
+ hlist_del(&obj->node);
+ hlist_add_head(&obj->node, &obj_pool);
+ obj_pool_free++;
+ obj_nr_tofree--;
+ }
+
+ /*
+ * Pool list is already full and there are still objs on the free
+ * list. Move remaining free objs to a temporary list to free the
+ * memory outside the pool_lock held region.
+ */
+ if (obj_nr_tofree) {
+ hlist_move_list(&obj_to_free, &tofree);
+ debug_objects_freed += obj_nr_tofree;
+ obj_nr_tofree = 0;
}
raw_spin_unlock_irqrestore(&pool_lock, flags);
+
+ hlist_for_each_entry_safe(obj, tmp, &tofree, node) {
+ hlist_del(&obj->node);
+ kmem_cache_free(obj_cache, obj);
+ }
}

-/*
- * Put the object back into the pool and schedule work to free objects
- * if necessary.
- */
-static void free_object(struct debug_obj *obj)
+static bool __free_object(struct debug_obj *obj)
{
unsigned long flags;
- int sched = 0;
+ bool work;

raw_spin_lock_irqsave(&pool_lock, flags);
- /*
- * schedule work when the pool is filled and the cache is
- * initialized:
- */
- if (obj_pool_free > debug_objects_pool_size && obj_cache)
- sched = 1;
- hlist_add_head(&obj->node, &obj_pool);
- obj_pool_free++;
+ work = (obj_pool_free > debug_objects_pool_size) && obj_cache;
obj_pool_used--;
+
+ if (work) {
+ obj_nr_tofree++;
+ hlist_add_head(&obj->node, &obj_to_free);
+ } else {
+ obj_pool_free++;
+ hlist_add_head(&obj->node, &obj_pool);
+ }
raw_spin_unlock_irqrestore(&pool_lock, flags);
- if (sched)
+ return work;
+}
+
+/*
+ * Put the object back into the pool and schedule work to free objects
+ * if necessary.
+ */
+static void free_object(struct debug_obj *obj)
+{
+ if (__free_object(obj))
schedule_work(&debug_obj_work);
}

@@ -714,13 +752,13 @@ EXPORT_SYMBOL_GPL(debug_object_active_state);
static void __debug_check_no_obj_freed(const void *address, unsigned long size)
{
unsigned long flags, oaddr, saddr, eaddr, paddr, chunks;
- struct hlist_node *tmp;
- HLIST_HEAD(freelist);
struct debug_obj_descr *descr;
enum debug_obj_state state;
struct debug_bucket *db;
+ struct hlist_node *tmp;
struct debug_obj *obj;
- int cnt;
+ int cnt, objs_checked = 0;
+ bool work = false;

saddr = (unsigned long) address;
eaddr = saddr + size;
@@ -751,21 +789,24 @@ static void __debug_check_no_obj_freed(const void *address, unsigned long size)
goto repeat;
default:
hlist_del(&obj->node);
- hlist_add_head(&obj->node, &freelist);
+ work |= __free_object(obj);
break;
}
}
raw_spin_unlock_irqrestore(&db->lock, flags);

- /* Now free them */
- hlist_for_each_entry_safe(obj, tmp, &freelist, node) {
- hlist_del(&obj->node);
- free_object(obj);
- }
-
if (cnt > debug_objects_maxchain)
debug_objects_maxchain = cnt;
+
+ objs_checked += cnt;
}
+
+ if (objs_checked > debug_objects_maxchecked)
+ debug_objects_maxchecked = objs_checked;
+
+ /* Schedule work to actually kmem_cache_free() objects */
+ if (work)
+ schedule_work(&debug_obj_work);
}

void debug_check_no_obj_freed(const void *address, unsigned long size)
@@ -780,12 +821,14 @@ void debug_check_no_obj_freed(const void *address, unsigned long size)
static int debug_stats_show(struct seq_file *m, void *v)
{
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", obj_pool_free);
seq_printf(m, "pool_min_free :%d\n", obj_pool_min_free);
seq_printf(m, "pool_used :%d\n", obj_pool_used);
seq_printf(m, "pool_max_used :%d\n", obj_pool_max_used);
+ seq_printf(m, "on_free_list :%d\n", obj_nr_tofree);
seq_printf(m, "objs_allocated:%d\n", debug_objects_allocated);
seq_printf(m, "objs_freed :%d\n", debug_objects_freed);
return 0;