[PATCH v3 3/7] mm, slab: allocate off-slab freelists as reclaimable when appropriate

From: Vlastimil Babka
Date: Wed Jul 18 2018 - 09:36:52 EST


In SLAB, OFF_SLAB caches allocate management structures (currently just the
freelist) from kmalloc caches when placement in a slab page together with
objects would lead to suboptimal memory usage. For SLAB_RECLAIM_ACCOUNT caches,
we can allocate the freelists from the newly introduced reclaimable kmalloc
caches, because shrinking the OFF_SLAB cache will in general result to freeing
of the freelists as well. This should improve accounting and anti-fragmentation
a bit.

Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
---
mm/slab.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/mm/slab.c b/mm/slab.c
index 9515798f37b2..99d779ba2b92 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2140,8 +2140,13 @@ int __kmem_cache_create(struct kmem_cache *cachep, slab_flags_t flags)
#endif

if (OFF_SLAB(cachep)) {
+ /*
+ * If this cache is reclaimable, allocate also freelists from
+ * a reclaimable kmalloc cache.
+ */
cachep->freelist_cache =
- kmalloc_slab(cachep->freelist_size, 0u);
+ kmalloc_slab(cachep->freelist_size,
+ cachep->allocflags & __GFP_RECLAIMABLE);
}

err = setup_cpu_cache(cachep, gfp);
--
2.18.0