To become a off slab, there are some constraints to avoid
bootstrapping problem and recursive call. This can be avoided differently
by simply checking that corresponding kmalloc cache is ready and it's not
a off slab. It would be more robust because static size checking can be
affected by cache size change or architecture type but dynamic checking
isn't.
One check 'freelist_cache->size > cachep->size / 2' is added to check
benefit of choosing off slab, because, now, there is no size constraint
which ensures enough advantage when selecting off slab.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
---
mm/slab.c | 45 +++++++++++++++++----------------------------
1 file changed, 17 insertions(+), 28 deletions(-)
diff --git a/mm/slab.c b/mm/slab.c
index b0f6eda..e86977e 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -272,7 +272,6 @@ static void kmem_cache_node_init(struct kmem_cache_node *parent)
#define CFLGS_OFF_SLAB (0x80000000UL)
#define OFF_SLAB(x) ((x)->flags & CFLGS_OFF_SLAB)
-#define OFF_SLAB_MIN_SIZE (max_t(size_t, PAGE_SIZE >> 5, KMALLOC_MIN_SIZE + 1))
#define BATCHREFILL_LIMIT 16
/*
@@ -1880,7 +1879,6 @@ static void slabs_destroy(struct kmem_cache *cachep, struct list_head *list)
static size_t calculate_slab_order(struct kmem_cache *cachep,
size_t size, unsigned long flags)
{
- unsigned long offslab_limit;
size_t left_over = 0;
int gfporder;
@@ -1897,16 +1895,24 @@ static size_t calculate_slab_order(struct kmem_cache *cachep,
break;
if (flags & CFLGS_OFF_SLAB) {
+ struct kmem_cache *freelist_cache;
+ size_t freelist_size;
+
+ freelist_size = num * sizeof(freelist_idx_t);
+ freelist_cache = kmalloc_slab(freelist_size, 0u);
+ if (!freelist_cache)
+ continue;
+
/*
- * Max number of objs-per-slab for caches which
- * use off-slab slabs. Needed to avoid a possible
- * looping condition in cache_grow().
+ * Needed to avoid possible looping condition
+ * in cache_grow()
*/
- offslab_limit = size;
- offslab_limit /= sizeof(freelist_idx_t);
+ if (OFF_SLAB(freelist_cache))
+ continue;
- if (num > offslab_limit)
- break;
+ /* check if off slab has enough benefit */
+ if (freelist_cache->size > cachep->size / 2)
+ continue;
}
/* Found something acceptable - save it away */
@@ -2032,17 +2038,9 @@ static bool set_off_slab_cache(struct kmem_cache *cachep,
cachep->num = 0;
/*
- * Determine if the slab management is 'on' or 'off' slab.
- * (bootstrapping cannot cope with offslab caches so don't do
- * it too early on. Always use on-slab management when
- * SLAB_NOLEAKTRACE to avoid recursive calls into kmemleak)
+ * Always use on-slab management when SLAB_NOLEAKTRACE
+ * to avoid recursive calls into kmemleak.
*/
- if (size < OFF_SLAB_MIN_SIZE)
- return false;
-
- if (slab_early_init)
- return false;
-
if (flags & SLAB_NOLEAKTRACE)
return false;
@@ -2206,7 +2204,6 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
* sized slab is initialized in current slab initialization sequence.
*/
if (debug_pagealloc_enabled() && (flags & SLAB_POISON) &&
- !slab_early_init && size >= kmalloc_size(INDEX_NODE) &&
size >= 256 && cachep->object_size > cache_line_size()) {
if (size < PAGE_SIZE || size % PAGE_SIZE == 0) {
size_t tmp_size = ALIGN(size, PAGE_SIZE);
@@ -2255,14 +2252,6 @@ done:
if (OFF_SLAB(cachep)) {
cachep->freelist_cache =
kmalloc_slab(cachep->freelist_size, 0u);
- /*
- * This is a possibility for one of the kmalloc_{dma,}_caches.
- * But since we go off slab only for object size greater than
- * OFF_SLAB_MIN_SIZE, and kmalloc_{dma,}_caches get created
- * in ascending order,this should not happen at all.
- * But leave a BUG_ON for some lucky dude.
- */
- BUG_ON(ZERO_OR_NULL_PTR(cachep->freelist_cache));
}
err = setup_cpu_cache(cachep, gfp);
--
1.9.1
--
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