From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756718Ab2D0GAz (ORCPT ); Fri, 27 Apr 2012 02:00:55 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:54570 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755874Ab2D0GAw (ORCPT ); Fri, 27 Apr 2012 02:00:52 -0400 X-SecurityPolicyCheck: OK by SHieldMailChecker v1.7.4 Message-ID: <4F9A359C.10107@jp.fujitsu.com> Date: Fri, 27 Apr 2012 14:58:52 +0900 From: KAMEZAWA Hiroyuki User-Agent: Mozilla/5.0 (Windows NT 6.0; rv:12.0) Gecko/20120420 Thunderbird/12.0 MIME-Version: 1.0 To: Linux Kernel CC: "linux-mm@kvack.org" , "cgroups@vger.kernel.org" , Michal Hocko , Johannes Weiner , Frederic Weisbecker , Glauber Costa , Tejun Heo , Han Ying , "Aneesh Kumar K.V" , Andrew Morton , kamezawa.hiroyuki@gmail.com Subject: [RFC][PATCH 5/9 v2] move charges to root at rmdir if use_hierarchy is unset References: <4F9A327A.6050409@jp.fujitsu.com> In-Reply-To: <4F9A327A.6050409@jp.fujitsu.com> Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Now, at removal of cgroup, ->pre_destroy() is called and move charges to the parent cgroup. A major reason of -EBUSY returned by ->pre_destroy() is that the 'moving' hits parent's resource limitation. It happens only when use_hierarchy=0. This was a mistake of original design.(it's me...) Considering use_hierarchy=0, all cgroups are treated as flat. So, no one cannot justify moving charges to parent...parent and children are in flat configuration, not hierarchical. This patch modifes to move charges to root cgroup at rmdir/force_empty if use_hierarchy==0. This will much simplify rmdir() and reduce error in ->pre_destroy. Signed-off-by: KAMEZAWA Hiroyuki --- Documentation/cgroups/memory.txt | 12 ++++++---- mm/memcontrol.c | 39 +++++++++++++------------------------ 2 files changed, 21 insertions(+), 30 deletions(-) diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt index 54c338d..82ce1ef 100644 --- a/Documentation/cgroups/memory.txt +++ b/Documentation/cgroups/memory.txt @@ -393,14 +393,14 @@ cgroup might have some charge associated with it, even though all tasks have migrated away from it. (because we charge against pages, not against tasks.) -Such charges are freed or moved to their parent. At moving, both of RSS -and CACHES are moved to parent. -rmdir() may return -EBUSY if freeing/moving fails. See 5.1 also. +Such charges are freed or moved to their parent if use_hierarchy=1. +if use_hierarchy=0, the charges will be moved to root cgroup. Charges recorded in swap information is not updated at removal of cgroup. Recorded information is discarded and a cgroup which uses swap (swapcache) will be charged as a new owner of it. +About use_hierarchy, see Section 6. 5. Misc. interfaces. @@ -413,13 +413,15 @@ will be charged as a new owner of it. Almost all pages tracked by this memory cgroup will be unmapped and freed. Some pages cannot be freed because they are locked or in-use. Such pages are - moved to parent and this cgroup will be empty. This may return -EBUSY if - VM is too busy to free/move all pages immediately. + moved to parent(if use_hierarchy==1) or root (if use_hierarchy==0) and this + cgroup will be empty. Typical use case of this interface is that calling this before rmdir(). Because rmdir() moves all pages to parent, some out-of-use page caches can be moved to the parent. If you want to avoid that, force_empty will be useful. + About use_hierarchy, see Section 6. + 5.2 stat file memory.stat file includes following statistics diff --git a/mm/memcontrol.c b/mm/memcontrol.c index ed53d64..62200f1 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2695,32 +2695,23 @@ static int mem_cgroup_move_parent(struct page *page, nr_pages = hpage_nr_pages(page); parent = mem_cgroup_from_cont(pcg); - if (!parent->use_hierarchy) { - ret = __mem_cgroup_try_charge(NULL, - gfp_mask, nr_pages, &parent, false); - if (ret) - goto put_back; - } + /* + * if use_hierarchy==0, move charges to root cgroup. + * in root cgroup, we don't touch res_counter + */ + if (!parent->use_hierarchy) + parent = root_mem_cgroup; if (nr_pages > 1) flags = compound_lock_irqsave(page); - if (parent->use_hierarchy) { - ret = mem_cgroup_move_account(page, nr_pages, - pc, child, parent, false); - if (!ret) - __mem_cgroup_cancel_local_charge(child, nr_pages); - } else { - ret = mem_cgroup_move_account(page, nr_pages, - pc, child, parent, true); - - if (ret) - __mem_cgroup_cancel_charge(parent, nr_pages); - } + ret = mem_cgroup_move_account(page, nr_pages, + pc, child, parent, false); + if (!ret) + __mem_cgroup_cancel_local_charge(child, nr_pages); if (nr_pages > 1) compound_unlock_irqrestore(page, flags); -put_back: putback_lru_page(page); put: put_page(page); @@ -3338,12 +3329,10 @@ int mem_cgroup_move_hugetlb_parent(int idx, struct cgroup *cgroup, csize = PAGE_SIZE << compound_order(page); /* If parent->use_hierarchy == 0, we need to charge parent */ if (!parent->use_hierarchy) { - ret = res_counter_charge(&parent->hugepage[idx], - csize, &fail_res); - if (ret) { - ret = -EBUSY; - goto err_out; - } + parent = root_mem_cgroup; + /* root has no limit */ + res_counter_charge_nofail(&parent->hugepage[idx], + csize, &fail_res); } counter = &memcg->hugepage[idx]; res_counter_uncharge_until(counter, counter->parent, csize); -- 1.7.4.1