[PATCH RFC v2 20/20] mm/slub: cleanup and repurpose some stat items

[Vlastimil Babka <vbabka@suse.cz>]

A number of stat items related to cpu slabs became unused, remove them.

Two of those were ALLOC_FASTPATH and FREE_FASTPATH. But instead of
removing those, use them instead of ALLOC_PCS and FREE_PCS, since
sheaves are the new (and only) fastpaths, Remove the recently added
_PCS variants instead.

Change where FREE_SLOWPATH is counted so that it only counts freeing of
objects by slab users that (for whatever reason) do not go to a percpu
sheaf, and not all (including internal) callers of __slab_free(). Thus
flushing sheaves (counted by SHEAF_FLUSH) no longer also increments
FREE_SLOWPATH. This matches how ALLOC_SLOWPATH doesn't count sheaf
refills (counted by SHEAF_REFILL).

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
 mm/slub.c | 77 +++++++++++++++++----------------------------------------------
 1 file changed, 21 insertions(+), 56 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index a473fa29a905..70314c72773e 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -330,33 +330,19 @@ enum add_mode {
 };
 
 enum stat_item {
-	ALLOC_PCS,		/* Allocation from percpu sheaf */
-	ALLOC_FASTPATH,		/* Allocation from cpu slab */
-	ALLOC_SLOWPATH,		/* Allocation by getting a new cpu slab */
-	FREE_PCS,		/* Free to percpu sheaf */
+	ALLOC_FASTPATH,		/* Allocation from percpu sheaves */
+	ALLOC_SLOWPATH,		/* Allocation from partial or new slab */
 	FREE_RCU_SHEAF,		/* Free to rcu_free sheaf */
 	FREE_RCU_SHEAF_FAIL,	/* Failed to free to a rcu_free sheaf */
-	FREE_FASTPATH,		/* Free to cpu slab */
-	FREE_SLOWPATH,		/* Freeing not to cpu slab */
+	FREE_FASTPATH,		/* Free to percpu sheaves */
+	FREE_SLOWPATH,		/* Free to a slab */
 	FREE_ADD_PARTIAL,	/* Freeing moves slab to partial list */
 	FREE_REMOVE_PARTIAL,	/* Freeing removes last object */
-	ALLOC_FROM_PARTIAL,	/* Cpu slab acquired from node partial list */
-	ALLOC_SLAB,		/* Cpu slab acquired from page allocator */
-	ALLOC_REFILL,		/* Refill cpu slab from slab freelist */
-	ALLOC_NODE_MISMATCH,	/* Switching cpu slab */
+	ALLOC_SLAB,		/* New slab acquired from page allocator */
+	ALLOC_NODE_MISMATCH,	/* Requested node different from cpu sheaf */
 	FREE_SLAB,		/* Slab freed to the page allocator */
-	CPUSLAB_FLUSH,		/* Abandoning of the cpu slab */
-	DEACTIVATE_FULL,	/* Cpu slab was full when deactivated */
-	DEACTIVATE_EMPTY,	/* Cpu slab was empty when deactivated */
-	DEACTIVATE_REMOTE_FREES,/* Slab contained remotely freed objects */
-	DEACTIVATE_BYPASS,	/* Implicit deactivation */
 	ORDER_FALLBACK,		/* Number of times fallback was necessary */
-	CMPXCHG_DOUBLE_CPU_FAIL,/* Failures of this_cpu_cmpxchg_double */
 	CMPXCHG_DOUBLE_FAIL,	/* Failures of slab freelist update */
-	CPU_PARTIAL_ALLOC,	/* Used cpu partial on alloc */
-	CPU_PARTIAL_FREE,	/* Refill cpu partial on free */
-	CPU_PARTIAL_NODE,	/* Refill cpu partial from node partial */
-	CPU_PARTIAL_DRAIN,	/* Drain cpu partial to node partial */
 	SHEAF_FLUSH,		/* Objects flushed from a sheaf */
 	SHEAF_REFILL,		/* Objects refilled to a sheaf */
 	SHEAF_ALLOC,		/* Allocation of an empty sheaf */
@@ -4330,8 +4316,10 @@ void *alloc_from_pcs(struct kmem_cache *s, gfp_t gfp, int node)
 	 * We assume the percpu sheaves contain only local objects although it's
 	 * not completely guaranteed, so we verify later.
 	 */
-	if (unlikely(node_requested && node != numa_mem_id()))
+	if (unlikely(node_requested && node != numa_mem_id())) {
+		stat(s, ALLOC_NODE_MISMATCH);
 		return NULL;
+	}
 
 	if (!local_trylock(&s->cpu_sheaves->lock))
 		return NULL;
@@ -4354,6 +4342,7 @@ void *alloc_from_pcs(struct kmem_cache *s, gfp_t gfp, int node)
 		 */
 		if (page_to_nid(virt_to_page(object)) != node) {
 			local_unlock(&s->cpu_sheaves->lock);
+			stat(s, ALLOC_NODE_MISMATCH);
 			return NULL;
 		}
 	}
@@ -4362,7 +4351,7 @@ void *alloc_from_pcs(struct kmem_cache *s, gfp_t gfp, int node)
 
 	local_unlock(&s->cpu_sheaves->lock);
 
-	stat(s, ALLOC_PCS);
+	stat(s, ALLOC_FASTPATH);
 
 	return object;
 }
@@ -4434,7 +4423,7 @@ unsigned int alloc_from_pcs_bulk(struct kmem_cache *s, gfp_t gfp, size_t size,
 
 	local_unlock(&s->cpu_sheaves->lock);
 
-	stat_add(s, ALLOC_PCS, batch);
+	stat_add(s, ALLOC_FASTPATH, batch);
 
 	allocated += batch;
 
@@ -5101,8 +5090,6 @@ static void __slab_free(struct kmem_cache *s, struct slab *slab,
 	unsigned long flags;
 	bool on_node_partial;
 
-	stat(s, FREE_SLOWPATH);
-
 	if (IS_ENABLED(CONFIG_SLUB_TINY) || kmem_cache_debug(s)) {
 		free_to_partial_list(s, slab, head, tail, cnt, addr);
 		return;
@@ -5408,7 +5395,7 @@ bool free_to_pcs(struct kmem_cache *s, void *object, bool allow_spin)
 
 	local_unlock(&s->cpu_sheaves->lock);
 
-	stat(s, FREE_PCS);
+	stat(s, FREE_FASTPATH);
 
 	return true;
 }
@@ -5659,7 +5646,7 @@ static void free_to_pcs_bulk(struct kmem_cache *s, size_t size, void **p)
 
 	local_unlock(&s->cpu_sheaves->lock);
 
-	stat_add(s, FREE_PCS, batch);
+	stat_add(s, FREE_FASTPATH, batch);
 
 	if (batch < size) {
 		p += batch;
@@ -5681,10 +5668,12 @@ static void free_to_pcs_bulk(struct kmem_cache *s, size_t size, void **p)
 	 */
 fallback:
 	__kmem_cache_free_bulk(s, size, p);
+	stat_add(s, FREE_SLOWPATH, size);
 
 flush_remote:
 	if (remote_nr) {
 		__kmem_cache_free_bulk(s, remote_nr, &remote_objects[0]);
+		stat_add(s, FREE_SLOWPATH, remote_nr);
 		if (i < size) {
 			remote_nr = 0;
 			goto next_remote_batch;
@@ -5777,6 +5766,7 @@ void slab_free(struct kmem_cache *s, struct slab *slab, void *object,
 	}
 
 	__slab_free(s, slab, object, object, 1, addr);
+	stat(s, FREE_SLOWPATH);
 }
 
 #ifdef CONFIG_MEMCG
@@ -5799,8 +5789,10 @@ void slab_free_bulk(struct kmem_cache *s, struct slab *slab, void *head,
 	 * With KASAN enabled slab_free_freelist_hook modifies the freelist
 	 * to remove objects, whose reuse must be delayed.
 	 */
-	if (likely(slab_free_freelist_hook(s, &head, &tail, &cnt)))
+	if (likely(slab_free_freelist_hook(s, &head, &tail, &cnt))) {
 		__slab_free(s, slab, head, tail, cnt, addr);
+		stat_add(s, FREE_SLOWPATH, cnt);
+	}
 }
 
 #ifdef CONFIG_SLUB_RCU_DEBUG
@@ -6699,6 +6691,7 @@ int __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
 		i = refill_objects(s, p, flags, size, size);
 		if (i < size)
 			goto error;
+		stat_add(s, ALLOC_SLOWPATH, i);
 	}
 
 	return i;
@@ -8698,33 +8691,19 @@ static ssize_t text##_store(struct kmem_cache *s,		\
 }								\
 SLAB_ATTR(text);						\
 
-STAT_ATTR(ALLOC_PCS, alloc_cpu_sheaf);
 STAT_ATTR(ALLOC_FASTPATH, alloc_fastpath);
 STAT_ATTR(ALLOC_SLOWPATH, alloc_slowpath);
-STAT_ATTR(FREE_PCS, free_cpu_sheaf);
 STAT_ATTR(FREE_RCU_SHEAF, free_rcu_sheaf);
 STAT_ATTR(FREE_RCU_SHEAF_FAIL, free_rcu_sheaf_fail);
 STAT_ATTR(FREE_FASTPATH, free_fastpath);
 STAT_ATTR(FREE_SLOWPATH, free_slowpath);
 STAT_ATTR(FREE_ADD_PARTIAL, free_add_partial);
 STAT_ATTR(FREE_REMOVE_PARTIAL, free_remove_partial);
-STAT_ATTR(ALLOC_FROM_PARTIAL, alloc_from_partial);
 STAT_ATTR(ALLOC_SLAB, alloc_slab);
-STAT_ATTR(ALLOC_REFILL, alloc_refill);
 STAT_ATTR(ALLOC_NODE_MISMATCH, alloc_node_mismatch);
 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_REMOTE_FREES, deactivate_remote_frees);
-STAT_ATTR(DEACTIVATE_BYPASS, deactivate_bypass);
 STAT_ATTR(ORDER_FALLBACK, order_fallback);
-STAT_ATTR(CMPXCHG_DOUBLE_CPU_FAIL, cmpxchg_double_cpu_fail);
 STAT_ATTR(CMPXCHG_DOUBLE_FAIL, cmpxchg_double_fail);
-STAT_ATTR(CPU_PARTIAL_ALLOC, cpu_partial_alloc);
-STAT_ATTR(CPU_PARTIAL_FREE, cpu_partial_free);
-STAT_ATTR(CPU_PARTIAL_NODE, cpu_partial_node);
-STAT_ATTR(CPU_PARTIAL_DRAIN, cpu_partial_drain);
 STAT_ATTR(SHEAF_FLUSH, sheaf_flush);
 STAT_ATTR(SHEAF_REFILL, sheaf_refill);
 STAT_ATTR(SHEAF_ALLOC, sheaf_alloc);
@@ -8800,33 +8779,19 @@ static struct attribute *slab_attrs[] = {
 	&remote_node_defrag_ratio_attr.attr,
 #endif
 #ifdef CONFIG_SLUB_STATS
-	&alloc_cpu_sheaf_attr.attr,
 	&alloc_fastpath_attr.attr,
 	&alloc_slowpath_attr.attr,
-	&free_cpu_sheaf_attr.attr,
 	&free_rcu_sheaf_attr.attr,
 	&free_rcu_sheaf_fail_attr.attr,
 	&free_fastpath_attr.attr,
 	&free_slowpath_attr.attr,
 	&free_add_partial_attr.attr,
 	&free_remove_partial_attr.attr,
-	&alloc_from_partial_attr.attr,
 	&alloc_slab_attr.attr,
-	&alloc_refill_attr.attr,
 	&alloc_node_mismatch_attr.attr,
 	&free_slab_attr.attr,
-	&cpuslab_flush_attr.attr,
-	&deactivate_full_attr.attr,
-	&deactivate_empty_attr.attr,
-	&deactivate_remote_frees_attr.attr,
-	&deactivate_bypass_attr.attr,
 	&order_fallback_attr.attr,
 	&cmpxchg_double_fail_attr.attr,
-	&cmpxchg_double_cpu_fail_attr.attr,
-	&cpu_partial_alloc_attr.attr,
-	&cpu_partial_free_attr.attr,
-	&cpu_partial_node_attr.attr,
-	&cpu_partial_drain_attr.attr,
 	&sheaf_flush_attr.attr,
 	&sheaf_refill_attr.attr,
 	&sheaf_alloc_attr.attr,

-- 
2.52.0