On 11/21/22 18:11, Vlastimil Babka wrote:
> Distinguishing kmalloc(__GFP_RECLAIMABLE) can help against fragmentation
> by grouping pages by mobility, but on tiny systems the extra memory
> overhead of separate set of kmalloc-rcl caches will probably be worse,
> and mobility grouping likely disabled anyway.
>
> Thus with CONFIG_SLUB_TINY, don't create kmalloc-rcl caches and use the
> regular ones.
>
> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Fixed up in response to lkp report for a MEMCG_KMEM+SLUB_TINY combo:
---8<---
>From c1ec0b924850a2863d061f316615d596176f15bb Mon Sep 17 00:00:00 2001
From: Vlastimil Babka <vbabka@xxxxxxx>
Date: Tue, 15 Nov 2022 18:19:28 +0100
Subject: [PATCH 06/12] mm, slub: don't create kmalloc-rcl caches with
CONFIG_SLUB_TINY
Distinguishing kmalloc(__GFP_RECLAIMABLE) can help against fragmentation
by grouping pages by mobility, but on tiny systems the extra memory
overhead of separate set of kmalloc-rcl caches will probably be worse,
and mobility grouping likely disabled anyway.
Thus with CONFIG_SLUB_TINY, don't create kmalloc-rcl caches and use the
regular ones.
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
---
include/linux/slab.h | 9 +++++++--
mm/slab_common.c | 10 ++++++++--
2 files changed, 15 insertions(+), 4 deletions(-)
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 45efc6c553b8..ae2d19ec8467 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -336,12 +336,17 @@ enum kmalloc_cache_type {
#endif
#ifndef CONFIG_MEMCG_KMEM
KMALLOC_CGROUP = KMALLOC_NORMAL,
-#else
- KMALLOC_CGROUP,
#endif
+#ifdef CONFIG_SLUB_TINY
+ KMALLOC_RECLAIM = KMALLOC_NORMAL,
+#else
KMALLOC_RECLAIM,
+#endif
#ifdef CONFIG_ZONE_DMA
KMALLOC_DMA,
+#endif
+#ifdef CONFIG_MEMCG_KMEM
+ KMALLOC_CGROUP,
#endif
NR_KMALLOC_TYPES
};
diff --git a/mm/slab_common.c b/mm/slab_common.c
index a8cb5de255fc..907d52963806 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -770,10 +770,16 @@ EXPORT_SYMBOL(kmalloc_size_roundup);
#define KMALLOC_CGROUP_NAME(sz)
#endif
+#ifndef CONFIG_SLUB_TINY
+#define KMALLOC_RCL_NAME(sz) .name[KMALLOC_RECLAIM] = "kmalloc-rcl-" #sz,
+#else
+#define KMALLOC_RCL_NAME(sz)
+#endif
+
#define INIT_KMALLOC_INFO(__size, __short_size) \
{ \
.name[KMALLOC_NORMAL] = "kmalloc-" #__short_size, \
- .name[KMALLOC_RECLAIM] = "kmalloc-rcl-" #__short_size, \
+ KMALLOC_RCL_NAME(__short_size) \
KMALLOC_CGROUP_NAME(__short_size) \
KMALLOC_DMA_NAME(__short_size) \
.size = __size, \
@@ -859,7 +865,7 @@ void __init setup_kmalloc_cache_index_table(void)
static void __init
new_kmalloc_cache(int idx, enum kmalloc_cache_type type, slab_flags_t flags)
{
- if (type == KMALLOC_RECLAIM) {
+ if ((KMALLOC_RECLAIM != KMALLOC_NORMAL) && (type == KMALLOC_RECLAIM)) {
flags |= SLAB_RECLAIM_ACCOUNT;
} else if (IS_ENABLED(CONFIG_MEMCG_KMEM) && (type == KMALLOC_CGROUP)) {
if (mem_cgroup_kmem_disabled()) {
--
2.38.1
