The commit message of commit 7ced371971966 ("slub: Acquire_slab()
avoid loop") claims:
> Avoid the loop in acquire slab and simply fail if there is a conflict.
>
> This will cause the next page on the list to be considered.
However, get_partial_node() looks like this:
static void *get_partial_node(struct kmem_cache *s, struct kmem_cache_node *n,
struct kmem_cache_cpu *c, gfp_t flags)
{
struct page *page, *page2;
void *object = NULL;
unsigned int available = 0;
int objects;
[...]
spin_lock(&n->list_lock);
list_for_each_entry_safe(page, page2, &n->partial, slab_list) {
void *t;
[...]
t = acquire_slab(s, n, page, object == NULL, &objects);
if (!t)
break;
[...]
}
spin_unlock(&n->list_lock);
return object;
}
So actually, if the cmpxchg() fails, we'll entirely bail out of
get_partial_node() and might, if the system isn't NUMA, fall back to
allocating more memory with new_slab()? That seems to me like it might
cause fragmented slabs to slowly use more memory than they should over
time.
Should the loop in get_partial_node() be using "continue" instead of
"break" in that case, so that the rest of the partial list will be
considered as the commit message claims?
