[Devel] [PATCH -mm 1/4] sl[au]b: do not charge large allocations to memcg

[Vladimir Davydov]

We don't track any random page allocation, so we shouldn't track kmalloc
that falls back to the page allocator.

Signed-off-by: Vladimir Davydov <vdavydov at parallels.com>
Cc: Johannes Weiner <hannes at cmpxchg.org>
Cc: Michal Hocko <mhocko at suse.cz>
Cc: Glauber Costa <glommer at gmail.com>
Cc: Christoph Lameter <cl at linux-foundation.org>
Cc: Pekka Enberg <penberg at kernel.org>
---
 include/linux/slab.h |    2 +-
 mm/memcontrol.c      |   27 +--------------------------
 mm/slub.c            |    4 ++--
 3 files changed, 4 insertions(+), 29 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 3dd389aa91c7..8a928ff71d93 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -363,7 +363,7 @@ kmalloc_order(size_t size, gfp_t flags, unsigned int order)
 {
 	void *ret;
 
-	flags |= (__GFP_COMP | __GFP_KMEMCG);
+	flags |= __GFP_COMP;
 	ret = (void *) __get_free_pages(flags, order);
 	kmemleak_alloc(ret, size, 1, flags);
 	return ret;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b4b6aef562fa..81a162d01d4d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3528,35 +3528,10 @@ __memcg_kmem_newpage_charge(gfp_t gfp, struct mem_cgroup **_memcg, int order)
 
 	*_memcg = NULL;
 
-	/*
-	 * Disabling accounting is only relevant for some specific memcg
-	 * internal allocations. Therefore we would initially not have such
-	 * check here, since direct calls to the page allocator that are marked
-	 * with GFP_KMEMCG only happen outside memcg core. We are mostly
-	 * concerned with cache allocations, and by having this test at
-	 * memcg_kmem_get_cache, we are already able to relay the allocation to
-	 * the root cache and bypass the memcg cache altogether.
-	 *
-	 * There is one exception, though: the SLUB allocator does not create
-	 * large order caches, but rather service large kmallocs directly from
-	 * the page allocator. Therefore, the following sequence when backed by
-	 * the SLUB allocator:
-	 *
-	 *	memcg_stop_kmem_account();
-	 *	kmalloc(<large_number>)
-	 *	memcg_resume_kmem_account();
-	 *
-	 * would effectively ignore the fact that we should skip accounting,
-	 * since it will drive us directly to this function without passing
-	 * through the cache selector memcg_kmem_get_cache. Such large
-	 * allocations are extremely rare but can happen, for instance, for the
-	 * cache arrays. We bring this test here.
-	 */
-	if (!current->mm || current->memcg_kmem_skip_account)
+	if (!current->mm)
 		return true;
 
 	memcg = get_mem_cgroup_from_mm(current->mm);
-
 	if (!memcg_can_account_kmem(memcg)) {
 		css_put(&memcg->css);
 		return true;
diff --git a/mm/slub.c b/mm/slub.c
index 5e234f1f8853..c2e58a787443 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3325,7 +3325,7 @@ static void *kmalloc_large_node(size_t size, gfp_t flags, int node)
 	struct page *page;
 	void *ptr = NULL;
 
-	flags |= __GFP_COMP | __GFP_NOTRACK | __GFP_KMEMCG;
+	flags |= __GFP_COMP | __GFP_NOTRACK;
 	page = alloc_pages_node(node, flags, get_order(size));
 	if (page)
 		ptr = page_address(page);
@@ -3395,7 +3395,7 @@ void kfree(const void *x)
 	if (unlikely(!PageSlab(page))) {
 		BUG_ON(!PageCompound(page));
 		kfree_hook(x);
-		__free_memcg_kmem_pages(page, compound_order(page));
+		__free_pages(page, compound_order(page));
 		return;
 	}
 	slab_free(page->slab_cache, page, object, _RET_IP_);
-- 
1.7.10.4