From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id B3B206B005C for ; Thu, 15 Jan 2009 02:15:22 -0500 (EST) Message-ID: <496EE25E.3030703@cn.fujitsu.com> Date: Thu, 15 Jan 2009 15:14:38 +0800 From: Li Zefan MIME-Version: 1.0 Subject: Re: [RFC] [PATCH] memcg: fix infinite loop References: <496ED2B7.5050902@cn.fujitsu.com> <20090115061557.GD30358@balbir.in.ibm.com> <20090115153134.632ebc85.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20090115153134.632ebc85.kamezawa.hiroyu@jp.fujitsu.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: KAMEZAWA Hiroyuki Cc: balbir@linux.vnet.ibm.com, Daisuke Nishimura , "linux-mm@kvack.org" List-ID: KAMEZAWA Hiroyuki wrote: > On Thu, 15 Jan 2009 11:45:57 +0530 > Balbir Singh wrote: > >> * Li Zefan [2009-01-15 14:07:51]: >> >>> 1. task p1 is in /memcg/0 >>> 2. p1 does mmap(4096*2, MAP_LOCKED) >>> 3. echo 4096 > /memcg/0/memory.limit_in_bytes >>> >>> The above 'echo' will never return, unless p1 exited or freed the memory. >>> The cause is we can't reclaim memory from p1, so the while loop in >>> mem_cgroup_resize_limit() won't break. >>> >>> This patch fixes it by decrementing retry_count regardless the return value >>> of mem_cgroup_hierarchical_reclaim(). >>> >> The problem definitely seems to exist, shouldn't we fix reclaim to >> return 0, so that we know progress is not made and retry count >> decrements? >> > > The behavior is correct. And we already check signal_pending() in the loop. > Ctrl-C or SIGALARM will works better than checking retry count. But this behavior seems like a regression. Please try it in 2.6.28, you'll see it returns EBUSY immediately. Looks like the return value of mem_cgroup_hierarchical_reclaim() is buggy ? > But adding a new control file, memory.resize_timeout to check timeout is a choice. > > Second thought is. > thanks to Kosaki at el, LRU for locked pages is now visible in memory.stat > file. So, we may able to have clever way. > > == > unevictable = mem_cgroup_get_all_zonestat(mem, LRU_UNEVICLABLE); > if (newlimit < unevictable) > break; > == > But considering hierarchy, this can be complex. > please don't modify current behavior for a while, I'll try to write "hierarchical stat" > with CSS_ID patch set's easy hierarchy walk. > > Thanks, > -Kame > > -- 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