From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id A64C46B004F for ; Tue, 13 Jan 2009 05:39:30 -0500 (EST) Date: Tue, 13 Jan 2009 18:49:58 +0900 From: Daisuke Nishimura Subject: [PATCH 3/4] memcg: fix hierarchical reclaim Message-Id: <20090113184958.4baf965c.nishimura@mxp.nes.nec.co.jp> In-Reply-To: <20090113184533.6ffd2af9.nishimura@mxp.nes.nec.co.jp> References: <20090113184533.6ffd2af9.nishimura@mxp.nes.nec.co.jp> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Andrew Morton Cc: LKML , linux-mm , Balbir Singh , KAMEZAWA Hiroyuki , Pavel Emelyanov , Li Zefan , Paul Menage , nishimura@mxp.nes.nec.co.jp List-ID: 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. ChangeLog: RFC->v1 - add mem_cgroup_put of last_scanned_child at mem_cgroup_destroy. ChangeLog: v1->v2 - cleanup. move all mem_cgroup_get/put to the end of mem_cgroup_get_next_node. Signed-off-by: Daisuke Nishimura --- mm/memcontrol.c | 68 +++++++++++++++++++++++++++++------------------------- 1 files changed, 36 insertions(+), 32 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 7be9b35..322625f 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -633,7 +633,7 @@ 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; @@ -644,19 +644,16 @@ mem_cgroup_get_next_node(struct mem_cgroup *curr, struct mem_cgroup *root_mem) /* * Walk down to children */ - mem_cgroup_put(curr); cgroup = list_entry(curr_cgroup->children.next, struct cgroup, sibling); curr = mem_cgroup_from_cont(cgroup); - mem_cgroup_get(curr); goto done; } 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; } @@ -664,11 +661,9 @@ visit_parent: * Goto next sibling */ if (curr_cgroup->sibling.next != &curr_cgroup->parent->children) { - mem_cgroup_put(curr); cgroup = list_entry(curr_cgroup->sibling.next, struct cgroup, sibling); curr = mem_cgroup_from_cont(cgroup); - mem_cgroup_get(curr); goto done; } @@ -679,7 +674,6 @@ visit_parent: goto visit_parent; done: - root_mem->last_scanned_child = curr; return curr; } @@ -689,40 +683,46 @@ 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; + struct mem_cgroup *orig, *next; 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); + + orig = root_mem->last_scanned_child; + obsolete = mem_cgroup_is_obsolete(orig); + 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. We put it later. + */ + if (orig) + VM_BUG_ON(!obsolete); + next = NULL; goto done; } - if (!root_mem->last_scanned_child || obsolete) { - - if (obsolete && root_mem->last_scanned_child) - mem_cgroup_put(root_mem->last_scanned_child); - + if (!orig || obsolete) { cgroup = list_first_entry(&root_mem->css.cgroup->children, struct cgroup, sibling); - ret = mem_cgroup_from_cont(cgroup); - mem_cgroup_get(ret); + next = mem_cgroup_from_cont(cgroup); } else - ret = mem_cgroup_get_next_node(root_mem->last_scanned_child, - root_mem); + next = __mem_cgroup_get_next_node(orig, root_mem); done: - root_mem->last_scanned_child = ret; + if (next) + mem_cgroup_get(next); + root_mem->last_scanned_child = next; + if (orig) + mem_cgroup_put(orig); mutex_unlock(&mem_cgroup_subsys.hierarchy_mutex); - return ret; + return (next) ? next : root_mem; } static bool mem_cgroup_check_under_limit(struct mem_cgroup *mem) @@ -780,21 +780,18 @@ 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; } @@ -2254,7 +2251,14 @@ static void mem_cgroup_pre_destroy(struct cgroup_subsys *ss, static void mem_cgroup_destroy(struct cgroup_subsys *ss, struct cgroup *cont) { - mem_cgroup_put(mem_cgroup_from_cont(cont)); + struct mem_cgroup *mem = mem_cgroup_from_cont(cont); + struct mem_cgroup *last_scanned_child = mem->last_scanned_child; + + if (last_scanned_child) { + VM_BUG_ON(!mem_cgroup_is_obsolete(last_scanned_child)); + mem_cgroup_put(last_scanned_child); + } + mem_cgroup_put(mem); } static int mem_cgroup_populate(struct cgroup_subsys *ss, -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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