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 SMTP id F0BF26B004D for ; Thu, 24 Sep 2009 03:36:47 -0400 (EDT) Received: from m4.gw.fujitsu.co.jp ([10.0.50.74]) by fgwmail6.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id n8O7amBw002632 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Thu, 24 Sep 2009 16:36:48 +0900 Received: from smail (m4 [127.0.0.1]) by outgoing.m4.gw.fujitsu.co.jp (Postfix) with ESMTP id D062F45DE4D for ; Thu, 24 Sep 2009 16:36:47 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (s4.gw.fujitsu.co.jp [10.0.50.94]) by m4.gw.fujitsu.co.jp (Postfix) with ESMTP id 81CBE45DD75 for ; Thu, 24 Sep 2009 16:36:47 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id 447BEE1800B for ; Thu, 24 Sep 2009 16:36:47 +0900 (JST) Received: from m107.s.css.fujitsu.com (m107.s.css.fujitsu.com [10.249.87.107]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id A56D3E18005 for ; Thu, 24 Sep 2009 16:36:46 +0900 (JST) Date: Thu, 24 Sep 2009 16:34:40 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [RFC][PATCH 6/8] memcg: avoid oom during charge migration Message-Id: <20090924163440.758ead95.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20090924144902.f4e5854c.nishimura@mxp.nes.nec.co.jp> References: <20090917112304.6cd4e6f6.nishimura@mxp.nes.nec.co.jp> <20090917160103.1bcdddee.nishimura@mxp.nes.nec.co.jp> <20090924144214.508469d1.nishimura@mxp.nes.nec.co.jp> <20090924144902.f4e5854c.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: Daisuke Nishimura Cc: linux-mm , Balbir Singh , Paul Menage , Li Zefan List-ID: On Thu, 24 Sep 2009 14:49:02 +0900 Daisuke Nishimura wrote: > This charge migration feature has double charges on both "from" and "to" > mem_cgroup during charge migration. > This means unnecessary oom can happen because of charge migration. > > This patch tries to avoid such oom. > > Signed-off-by: Daisuke Nishimura > --- > mm/memcontrol.c | 19 +++++++++++++++++++ > 1 files changed, 19 insertions(+), 0 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index fbcc195..25de11c 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -287,6 +287,8 @@ struct migrate_charge { > unsigned long precharge; > }; > static struct migrate_charge *mc; > +static struct task_struct *mc_task; > +static DECLARE_WAIT_QUEUE_HEAD(mc_waitq); > > static void mem_cgroup_get(struct mem_cgroup *mem); > static void mem_cgroup_put(struct mem_cgroup *mem); > @@ -1317,6 +1319,7 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm, > while (1) { > int ret = 0; > unsigned long flags = 0; > + DEFINE_WAIT(wait); > > if (mem_cgroup_is_root(mem)) > goto done; > @@ -1358,6 +1361,17 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm, > if (mem_cgroup_check_under_limit(mem_over_limit)) > continue; > > + /* try to avoid oom while someone is migrating charge */ > + if (mc_task && current != mc_task) { Hmm, I like == if (mc && mc->to == mem) or if (mc) { if (mem is ancestor of mc->to) wait for a while == ? > + prepare_to_wait(&mc_waitq, &wait, TASK_INTERRUPTIBLE); > + if (mc) { > + schedule(); > + finish_wait(&mc_waitq, &wait); > + continue; > + } > + finish_wait(&mc_waitq, &wait); > + } > + > if (!nr_retries--) { > if (oom) { > mutex_lock(&memcg_tasklist); > @@ -3345,6 +3359,8 @@ static void mem_cgroup_clear_migrate_charge(void) > __mem_cgroup_cancel_charge(mc->to); > kfree(mc); > mc = NULL; > + mc_task = NULL; > + wake_up_all(&mc_waitq); > } Hmm. I think this wake_up is too late. How about waking up when we release page_table_lock() or once per vma ? Or, just skip nr_retries-- like if (mc && mc->to_is_not_ancestor(mem) && nr_retries--) { } ? I think page-reclaim war itself is not bad. (Anyway, we'll have to fix cgroup_lock if the move cost is a problem.) Thanks, -Kame > > static int mem_cgroup_can_migrate_charge(struct mem_cgroup *mem, > @@ -3354,6 +3370,7 @@ static int mem_cgroup_can_migrate_charge(struct mem_cgroup *mem, > struct mem_cgroup *from = mem_cgroup_from_task(p); > > VM_BUG_ON(mc); > + VM_BUG_ON(mc_task); > > if (from == mem) > return 0; > @@ -3367,6 +3384,8 @@ static int mem_cgroup_can_migrate_charge(struct mem_cgroup *mem, > mc->to = mem; > mc->precharge = 0; > > + mc_task = current; > + > ret = migrate_charge_prepare(); > > if (ret) > -- > 1.5.6.1 > > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org