[PATCH v4 21/22] mm/slub: remove DEACTIVATE_TO_* stat items

Vlastimil Babka
2026-01-23T06:54:22Z

The cpu slabs and their deactivations were removed, so remove the unused
stat items. Weirdly enough the values were also used to control
__add_partial() adding to head or tail of the list, so replace that with
a new enum add_mode, which is cleaner.

Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Hao Li <hao.li@linux.dev>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
mm/slub.c | 31 +++++++++++++++----------------
1 file changed, 15 insertions(+), 16 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 3009eb7bd8d2..369fb9bbdb75 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -329,6 +329,11 @@ static void debugfs_slab_add(struct kmem_cache *);
static inline void debugfs_slab_add(struct kmem_cache *s) { }
#endif

+enum add_mode {
+ ADD_TO_HEAD,
+ ADD_TO_TAIL,
+};
+
enum stat_item {
ALLOC_PCS, /* Allocation from percpu sheaf */
ALLOC_FASTPATH, /* Allocation from cpu slab */
@@ -348,8 +353,6 @@ enum stat_item {
CPUSLAB_FLUSH, /* Abandoning of the cpu slab */
DEACTIVATE_FULL, /* Cpu slab was full when deactivated */
DEACTIVATE_EMPTY, /* Cpu slab was empty when deactivated */
- DEACTIVATE_TO_HEAD, /* Cpu slab was moved to the head of partials */
- DEACTIVATE_TO_TAIL, /* Cpu slab was moved to the tail of partials */
DEACTIVATE_REMOTE_FREES,/* Slab contained remotely freed objects */
DEACTIVATE_BYPASS, /* Implicit deactivation */
ORDER_FALLBACK, /* Number of times fallback was necessary */
@@ -3270,10 +3273,10 @@ static inline void slab_clear_node_partial(struct slab *slab)
* Management of partially allocated slabs.
*/
static inline void
-__add_partial(struct kmem_cache_node *n, struct slab *slab, int tail)
+__add_partial(struct kmem_cache_node *n, struct slab *slab, enum add_mode mode)
{
n->nr_partial++;
- if (tail == DEACTIVATE_TO_TAIL)
+ if (mode == ADD_TO_TAIL)
list_add_tail(&slab->slab_list, &n->partial);
else
list_add(&slab->slab_list, &n->partial);
@@ -3281,10 +3284,10 @@ __add_partial(struct kmem_cache_node *n, struct slab *slab, int tail)
}

static inline void add_partial(struct kmem_cache_node *n,
- struct slab *slab, int tail)
+ struct slab *slab, enum add_mode mode)
{
lockdep_assert_held(&n->list_lock);
- __add_partial(n, slab, tail);
+ __add_partial(n, slab, mode);
}

static inline void remove_partial(struct kmem_cache_node *n,
@@ -3377,7 +3380,7 @@ static void *alloc_single_from_new_slab(struct kmem_cache *s, struct slab *slab,
if (slab->inuse == slab->objects)
add_full(s, n, slab);
else
- add_partial(n, slab, DEACTIVATE_TO_HEAD);
+ add_partial(n, slab, ADD_TO_HEAD);

inc_slabs_node(s, nid, slab->objects);
spin_unlock_irqrestore(&n->list_lock, flags);
@@ -3999,7 +4002,7 @@ static unsigned int alloc_from_new_slab(struct kmem_cache *s, struct slab *slab,
n = get_node(s, slab_nid(slab));
spin_lock_irqsave(&n->list_lock, flags);
}
- add_partial(n, slab, DEACTIVATE_TO_HEAD);
+ add_partial(n, slab, ADD_TO_HEAD);
spin_unlock_irqrestore(&n->list_lock, flags);
}

@@ -5070,7 +5073,7 @@ static noinline void free_to_partial_list(
/* was on full list */
remove_full(s, n, slab);
if (!slab_free) {
- add_partial(n, slab, DEACTIVATE_TO_TAIL);
+ add_partial(n, slab, ADD_TO_TAIL);
stat(s, FREE_ADD_PARTIAL);
}
} else if (slab_free) {
@@ -5190,7 +5193,7 @@ static void __slab_free(struct kmem_cache *s, struct slab *slab,
* then add it.
*/
if (unlikely(was_full)) {
- add_partial(n, slab, DEACTIVATE_TO_TAIL);
+ add_partial(n, slab, ADD_TO_TAIL);
stat(s, FREE_ADD_PARTIAL);
}
spin_unlock_irqrestore(&n->list_lock, flags);
@@ -6592,7 +6595,7 @@ __refill_objects_node(struct kmem_cache *s, void **p, gfp_t gfp, unsigned int mi
continue;

list_del(&slab->slab_list);
- add_partial(n, slab, DEACTIVATE_TO_HEAD);
+ add_partial(n, slab, ADD_TO_HEAD);
}

spin_unlock_irqrestore(&n->list_lock, flags);
@@ -7059,7 +7062,7 @@ static void early_kmem_cache_node_alloc(int node)
* No locks need to be taken here as it has just been
* initialized and there is no concurrent access.
*/
- __add_partial(n, slab, DEACTIVATE_TO_HEAD);
+ __add_partial(n, slab, ADD_TO_HEAD);
}

static void free_kmem_cache_nodes(struct kmem_cache *s)
@@ -8751,8 +8754,6 @@ STAT_ATTR(FREE_SLAB, free_slab);
STAT_ATTR(CPUSLAB_FLUSH, cpuslab_flush);
STAT_ATTR(DEACTIVATE_FULL, deactivate_full);
STAT_ATTR(DEACTIVATE_EMPTY, deactivate_empty);
-STAT_ATTR(DEACTIVATE_TO_HEAD, deactivate_to_head);
-STAT_ATTR(DEACTIVATE_TO_TAIL, deactivate_to_tail);
STAT_ATTR(DEACTIVATE_REMOTE_FREES, deactivate_remote_frees);
STAT_ATTR(DEACTIVATE_BYPASS, deactivate_bypass);
STAT_ATTR(ORDER_FALLBACK, order_fallback);
@@ -8855,8 +8856,6 @@ static struct attribute *slab_attrs[] = {
&cpuslab_flush_attr.attr,
&deactivate_full_attr.attr,
&deactivate_empty_attr.attr,
- &deactivate_to_head_attr.attr,
- &deactivate_to_tail_attr.attr,
&deactivate_remote_frees_attr.attr,
&deactivate_bypass_attr.attr,
&order_fallback_attr.attr,

--
2.52.0