linux-kernel - [PATCH 1/4] mm/slub: fix bulk alloc and free stats

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Message-Id: <20231204-slub-cleanup-hooks-v1-1-88b65f7cd9d5@suse.cz>
Date:   Mon, 04 Dec 2023 20:34:40 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH 1/4] mm/slub: fix bulk alloc and free stats

The SLUB sysfs stats enabled CONFIG_SLUB_STATS have two deficiencies
identified wrt bulk alloc/free operations:

- Bulk allocations from cpu freelist are not counted. Add the
  ALLOC_FASTPATH counter there.

- Bulk fastpath freeing will count a list of multiple objects with a
  single FREE_FASTPATH inc. Add a stat_add() variant to count them all.

Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 mm/slub.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/mm/slub.c b/mm/slub.c
index 3f8b95757106..d7b0ca6012e0 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -396,6 +396,14 @@ static inline void stat(const struct kmem_cache *s, enum stat_item si)
 #endif
 }
 
+static inline
+void stat_add(const struct kmem_cache *s, enum stat_item si, int v)
+{
+#ifdef CONFIG_SLUB_STATS
+	raw_cpu_add(s->cpu_slab->stat[si], v);
+#endif
+}
+
 /*
  * The slab lists for all objects.
  */
@@ -4268,7 +4276,7 @@ static __always_inline void do_slab_free(struct kmem_cache *s,
 
 		local_unlock(&s->cpu_slab->lock);
 	}
-	stat(s, FREE_FASTPATH);
+	stat_add(s, FREE_FASTPATH, cnt);
 }
 #else /* CONFIG_SLUB_TINY */
 static void do_slab_free(struct kmem_cache *s,
@@ -4545,6 +4553,7 @@ static inline int __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags,
 		c->freelist = get_freepointer(s, object);
 		p[i] = object;
 		maybe_wipe_obj_freeptr(s, p[i]);
+		stat(s, ALLOC_FASTPATH);
 	}
 	c->tid = next_tid(c->tid);
 	local_unlock_irqrestore(&s->cpu_slab->lock, irqflags);

-- 
2.43.0