Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756905AbZAIGFk (ORCPT ); Fri, 9 Jan 2009 01:05:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752359AbZAIGFc (ORCPT ); Fri, 9 Jan 2009 01:05:32 -0500 Received: from TYO201.gate.nec.co.jp ([202.32.8.193]:36582 "EHLO tyo201.gate.nec.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751125AbZAIGFb (ORCPT ); Fri, 9 Jan 2009 01:05:31 -0500 Date: Fri, 9 Jan 2009 15:01:03 +0900 From: Daisuke Nishimura To: balbir@linux.vnet.ibm.com Cc: nishimura@mxp.nes.nec.co.jp, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kamezawa.hiroyu@jp.fujitsu.com, lizf@cn.fujitsu.com, menage@google.com Subject: Re: [RFC][PATCH 3/4] memcg: fix for mem_cgroup_hierarchical_reclaim Message-Id: <20090109150103.25812a51.nishimura@mxp.nes.nec.co.jp> In-Reply-To: <20090109053323.GD9737@balbir.in.ibm.com> References: <20090108190818.b663ce20.nishimura@mxp.nes.nec.co.jp> <20090108191501.dc469a51.nishimura@mxp.nes.nec.co.jp> <20090109053323.GD9737@balbir.in.ibm.com> Organization: NEC Soft, Ltd. X-Mailer: Sylpheed 2.4.8 (GTK+ 2.10.14; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6072 Lines: 180 On Fri, 9 Jan 2009 11:03:23 +0530, Balbir Singh wrote: > * Daisuke Nishimura [2009-01-08 19:15:01]: > > > If root_mem has no children, last_scaned_child is set to root_mem itself. > > But after some children added to root_mem, mem_cgroup_get_next_node can > > mem_cgroup_put the root_mem although root_mem has not been mem_cgroup_get. > > > > Good catch! > Thanks :) > > This patch fixes this behavior by: > > - Set last_scanned_child to NULL if root_mem has no children or DFS search > > has returned to root_mem itself(root_mem is not a "child" of root_mem). > > Make mem_cgroup_get_first_node return root_mem in this case. > > There are no mem_cgroup_get/put for root_mem. > > - Rename mem_cgroup_get_next_node to __mem_cgroup_get_next_node, and > > mem_cgroup_get_first_node to mem_cgroup_get_next_node. > > Make mem_cgroup_hierarchical_reclaim call only new mem_cgroup_get_next_node. > > > > How have you tested these changes? When I wrote up the patches, I did > several tests to make sure that all nodes in the hierarchy are covered > while reclaiming in order. > I do something like: 1. mount memcg (at/cgroup/memory) 2. enable hierarchy (if testing use_hierarchy==1 case) 3. mkdir /cgroup/memory/01 4. run some programs in /cgroup/memory/01 5. select the next directory to move to at random from 01/, 01/aa, 01/bb, 02/, 02/aa and 02/bb. 6. move all processes to next directory. 7. remove the old directory if possible. 8. wait for an random period. 9. goto 5. Before this patch, I got sometimes general protection fault, which seemed to be caused by unexpected free of mem_cgroup (and reuse the area for another purpose). BTW, I think "mem_cgroup_put(mem->last_scanned_child)" is also needed at mem_cgroup_destroy to prevent memory leak. I'll update my patch later. Thanks, Daisuke Nishimura. > > > > Signed-off-by: Daisuke Nishimura > > --- > > mm/memcontrol.c | 37 +++++++++++++++++++++---------------- > > 1 files changed, 21 insertions(+), 16 deletions(-) > > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index 288e22c..dc38a0e 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -622,7 +622,7 @@ unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan, > > * called with hierarchy_mutex held > > */ > > static struct mem_cgroup * > > -mem_cgroup_get_next_node(struct mem_cgroup *curr, struct mem_cgroup *root_mem) > > +__mem_cgroup_get_next_node(struct mem_cgroup *curr, struct mem_cgroup *root_mem) > > { > > struct cgroup *cgroup, *curr_cgroup, *root_cgroup; > > > > @@ -644,8 +644,8 @@ mem_cgroup_get_next_node(struct mem_cgroup *curr, struct mem_cgroup *root_mem) > > visit_parent: > > if (curr_cgroup == root_cgroup) { > > mem_cgroup_put(curr); > > - curr = root_mem; > > - mem_cgroup_get(curr); > > + /* caller handles NULL case */ > > + curr = NULL; > > goto done; > > } > > > > @@ -668,7 +668,6 @@ visit_parent: > > goto visit_parent; > > > > done: > > - root_mem->last_scanned_child = curr; > > return curr; > > } > > > > @@ -678,20 +677,29 @@ done: > > * that to reclaim free pages from. > > */ > > static struct mem_cgroup * > > -mem_cgroup_get_first_node(struct mem_cgroup *root_mem) > > +mem_cgroup_get_next_node(struct mem_cgroup *root_mem) > > { > > struct cgroup *cgroup; > > struct mem_cgroup *ret; > > bool obsolete; > > > > - obsolete = mem_cgroup_is_obsolete(root_mem->last_scanned_child); > > - > > /* > > * Scan all children under the mem_cgroup mem > > */ > > mutex_lock(&mem_cgroup_subsys.hierarchy_mutex); > > + > > + obsolete = mem_cgroup_is_obsolete(root_mem->last_scanned_child); > > + > > if (list_empty(&root_mem->css.cgroup->children)) { > > - ret = root_mem; > > + /* > > + * root_mem might have children before and last_scanned_child > > + * may point to one of them. > > + */ > > + if (root_mem->last_scanned_child) { > > + VM_BUG_ON(!obsolete); > > + mem_cgroup_put(root_mem->last_scanned_child); > > + } > > + ret = NULL; > > goto done; > > } > > > > @@ -705,13 +713,13 @@ mem_cgroup_get_first_node(struct mem_cgroup *root_mem) > > ret = mem_cgroup_from_cont(cgroup); > > mem_cgroup_get(ret); > > } else > > - ret = mem_cgroup_get_next_node(root_mem->last_scanned_child, > > + ret = __mem_cgroup_get_next_node(root_mem->last_scanned_child, > > root_mem); > > > > done: > > root_mem->last_scanned_child = ret; > > mutex_unlock(&mem_cgroup_subsys.hierarchy_mutex); > > - return ret; > > + return (ret) ? ret : root_mem; > > } > > > > static bool mem_cgroup_check_under_limit(struct mem_cgroup *mem) > > @@ -769,21 +777,18 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem, > > if (!root_mem->use_hierarchy) > > return ret; > > > > - next_mem = mem_cgroup_get_first_node(root_mem); > > + next_mem = mem_cgroup_get_next_node(root_mem); > > > > while (next_mem != root_mem) { > > if (mem_cgroup_is_obsolete(next_mem)) { > > - mem_cgroup_put(next_mem); > > - next_mem = mem_cgroup_get_first_node(root_mem); > > + next_mem = mem_cgroup_get_next_node(root_mem); > > continue; > > } > > ret = try_to_free_mem_cgroup_pages(next_mem, gfp_mask, noswap, > > get_swappiness(next_mem)); > > if (mem_cgroup_check_under_limit(root_mem)) > > return 0; > > - mutex_lock(&mem_cgroup_subsys.hierarchy_mutex); > > - next_mem = mem_cgroup_get_next_node(next_mem, root_mem); > > - mutex_unlock(&mem_cgroup_subsys.hierarchy_mutex); > > + next_mem = mem_cgroup_get_next_node(root_mem); > > } > > return ret; > > } > > > > > Looks good to me, I need to test it though > > Acked-by: Balbir Singh > > -- > Balbir -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/