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Message-Id: <20260112-sheaves-for-all-v2-20-98225cfb50cf@suse.cz>
Date: Mon, 12 Jan 2026 16:17:14 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Harry Yoo <harry.yoo@...cle.com>, Petr Tesarik <ptesarik@...e.com>,
Christoph Lameter <cl@...two.org>, David Rientjes <rientjes@...gle.com>,
Roman Gushchin <roman.gushchin@...ux.dev>
Cc: Hao Li <hao.li@...ux.dev>, Andrew Morton <akpm@...ux-foundation.org>,
Uladzislau Rezki <urezki@...il.com>,
"Liam R. Howlett" <Liam.Howlett@...cle.com>,
Suren Baghdasaryan <surenb@...gle.com>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Alexei Starovoitov <ast@...nel.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, linux-rt-devel@...ts.linux.dev,
bpf@...r.kernel.org, kasan-dev@...glegroups.com,
Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH RFC v2 20/20] mm/slub: cleanup and repurpose some stat
items
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@...e.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
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