On Thu, Jan 07, 2016 at 03:03:38PM +0100, Jesper Dangaard Brouer wrote:
> This change is primarily an attempt to make it easier to realize the
> optimizations the compiler performs in-case CONFIG_MEMCG_KMEM is not
> enabled.
>
> Performance wise, even when CONFIG_MEMCG_KMEM is compiled in, the
> overhead is zero. This is because, as long as no process have
> enabled kmem cgroups accounting, the assignment is replaced by
> asm-NOP operations. This is possible because memcg_kmem_enabled()
> uses a static_key_false() construct.
>
> It also helps readability as it avoid accessing the p[] array like:
> p[size - 1] which "expose" that the array is processed backwards
> inside helper function build_detached_freelist().
That part is cleande up but overall code doesn't looks readable to me.
How about below change?
Thanks.
---------------------->8------------------
struct detached_freelist {
+ struct kmem_cache *s;
struct page *page;
void *tail;
void *freelist;
@@ -2852,8 +2853,11 @@ static int build_detached_freelist(struct kmem_cache *s, size_t size,
if (!object)
return 0;
+ /* Support for memcg */
+ df->s = cache_from_obj(s, object);
+
/* Start new detached freelist */
- set_freepointer(s, object, NULL);
+ set_freepointer(df.s, object, NULL);
df->page = virt_to_head_page(object);
df->tail = object;
df->freelist = object;
@@ -2868,7 +2872,7 @@ static int build_detached_freelist(struct kmem_cache *s, size_t size,
/* df->page is always set at this point */
if (df->page == virt_to_head_page(object)) {
/* Opportunity build freelist */
- set_freepointer(s, object, df->freelist);
+ set_freepointer(df.s, object, df->freelist);
df->freelist = object;
df->cnt++;
p[size] = NULL; /* mark object processed */
@@ -2889,23 +2893,19 @@ static int build_detached_freelist(struct kmem_cache *s, size_t size,
/* Note that interrupts must be enabled when calling this function. */
-void kmem_cache_free_bulk(struct kmem_cache *orig_s, size_t size, void **p)
+void kmem_cache_free_bulk(struct kmem_cache *s, size_t size, void **p)
{
if (WARN_ON(!size))
return;
do {
struct detached_freelist df;
- struct kmem_cache *s;
-
- /* Support for memcg */
- s = cache_from_obj(orig_s, p[size - 1]);
size = build_detached_freelist(s, size, p, &df);
if (unlikely(!df.page))
continue;
- slab_free(s, df.page, df.freelist, df.tail, df.cnt, _RET_IP_);
+ slab_free(df.s, df.page, df.freelist, df.tail, df.cnt, _RET_IP_);
} while (likely(size));
}
EXPORT_SYMBOL(kmem_cache_free_bulk);
--
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