From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932197AbaKENpr (ORCPT ); Wed, 5 Nov 2014 08:45:47 -0500 Received: from mx2.parallels.com ([199.115.105.18]:36045 "EHLO mx2.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754894AbaKENo4 (ORCPT ); Wed, 5 Nov 2014 08:44:56 -0500 From: Vladimir Davydov To: Andrew Morton CC: Johannes Weiner , Michal Hocko , , Subject: [PATCH -mm 3/3] memcg: only check memcg_kmem_skip_account in __memcg_kmem_get_cache Date: Wed, 5 Nov 2014 16:44:44 +0300 Message-ID: X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <9ac4c9e767d437f744bb61feb7e042c93c67f727.1415194280.git.vdavydov@parallels.com> References: <9ac4c9e767d437f744bb61feb7e042c93c67f727.1415194280.git.vdavydov@parallels.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org __memcg_kmem_get_cache can recurse if it calls kmalloc (which it does if the cgroup's kmem cache doesn't exist), because kmalloc may call __memcg_kmem_get_cache internally again. To avoid the recursion, we use the task_struct->memcg_kmem_skip_account flag. However, there's no need in checking the flag in memcg_kmem_newpage_charge or memcg_kmem_recharge_slab, because there's no way how these two functions could result in recursion, if called from memcg_kmem_get_cache. So let's remove the redundant code. Signed-off-by: Vladimir Davydov --- mm/memcontrol.c | 31 ------------------------------- 1 file changed, 31 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 52d1e933bb9f..d7de40cb3c8e 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2717,34 +2717,6 @@ __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 - * accounted to kmemcg (alloc_kmem_pages and friends) 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() - * 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->memcg_kmem_skip_account) - return true; - memcg = get_mem_cgroup_from_mm(current->mm); if (!memcg_kmem_is_active(memcg)) { @@ -2800,9 +2772,6 @@ int __memcg_kmem_recharge_slab(void *obj, gfp_t gfp) int nr_pages; int ret = 0; - if (current->memcg_kmem_skip_account) - goto out; - page = virt_to_head_page(obj); page_memcg = ACCESS_ONCE(page->mem_cgroup); -- 1.7.10.4