Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758353AbZAHLIS (ORCPT ); Thu, 8 Jan 2009 06:08:18 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753998AbZAHLIH (ORCPT ); Thu, 8 Jan 2009 06:08:07 -0500 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:56623 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752229AbZAHLIF (ORCPT ); Thu, 8 Jan 2009 06:08:05 -0500 Message-ID: <39822.10.75.179.62.1231412881.squirrel@webmail-b.css.fujitsu.com> In-Reply-To: <20090108191501.dc469a51.nishimura@mxp.nes.nec.co.jp> References: <20090108190818.b663ce20.nishimura@mxp.nes.nec.co.jp> <20090108191501.dc469a51.nishimura@mxp.nes.nec.co.jp> Date: Thu, 8 Jan 2009 20:08:01 +0900 (JST) Subject: Re: [RFC][PATCH 3/4] memcg: fix for mem_cgroup_hierarchical_reclaim From: "KAMEZAWA Hiroyuki" To: "Daisuke Nishimura" Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kamezawa.hiroyu@jp.fujitsu.com, balbir@linux.vnet.ibm.com, lizf@cn.fujitsu.com, menage@google.com, nishimura@mxp.nes.nec.co.jp User-Agent: SquirrelMail/1.4.3a X-Mailer: SquirrelMail/1.4.3a MIME-Version: 1.0 Content-Type: text/plain;charset=us-ascii Content-Transfer-Encoding: 8bit X-Priority: 3 (Normal) Importance: Normal Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5072 Lines: 157 Daisuke Nishimura said: > 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. > > 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. > > > Signed-off-by: Daisuke Nishimura Hmm, seems necessary fix. Then, it's better to rebase my patch on to this. Reviewed-by: KAMEZAWA Hiroyuki Maybe simpler one can be written but my patch remove all this out later.... Thanks, -Kame > --- > 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; > } > -- > 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/ > -- 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/