2023-06-13 10:58:50

by Vlastimil Babka

Subject: [PATCH] mm/slab_common: use SLAB_NO_MERGE instead of negative refcount

When CONFIG_MEMCG_KMEM is enabled, we disable cache merging for
KMALLOC_NORMAL so they don't end up merged with a cache that uses ad-hoc
__GFP_ACCOUNT. This was implemented by setting refcount to -1, but now
we have a proper SLAB_NO_MERGE flag, so use that instead.

Signed-off-by: Vlastimil Babka <[email protected]>
---
mm/slab_common.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 0e0a617eae7d..67caf0bc3194 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -878,17 +878,17 @@ new_kmalloc_cache(int idx, enum kmalloc_cache_type type, slab_flags_t flags)
flags |= SLAB_CACHE_DMA;
}

- kmalloc_caches[type][idx] = create_kmalloc_cache(
- kmalloc_info[idx].name[type],
- kmalloc_info[idx].size, flags, 0,
- kmalloc_info[idx].size);
-
/*
* If CONFIG_MEMCG_KMEM is enabled, disable cache merging for
* KMALLOC_NORMAL caches.
*/
if (IS_ENABLED(CONFIG_MEMCG_KMEM) && (type == KMALLOC_NORMAL))
- kmalloc_caches[type][idx]->refcount = -1;
+ flags |= SLAB_NO_MERGE;
+
+ kmalloc_caches[type][idx] = create_kmalloc_cache(
+ kmalloc_info[idx].name[type],
+ kmalloc_info[idx].size, flags, 0,
+ kmalloc_info[idx].size);
}

/*
--
2.41.0

2023-06-13 23:23:23

by David Rientjes

Subject: Re: [PATCH] mm/slab_common: use SLAB_NO_MERGE instead of negative refcount

On Tue, 13 Jun 2023, Vlastimil Babka wrote:

> When CONFIG_MEMCG_KMEM is enabled, we disable cache merging for
> KMALLOC_NORMAL so they don't end up merged with a cache that uses ad-hoc
> __GFP_ACCOUNT. This was implemented by setting refcount to -1, but now
> we have a proper SLAB_NO_MERGE flag, so use that instead.
>
> Signed-off-by: Vlastimil Babka <[email protected]>

Acked-by: David Rientjes <[email protected]>