Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752303Ab0HZDZb (ORCPT ); Wed, 25 Aug 2010 23:25:31 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:45416 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751460Ab0HZDZ3 (ORCPT ); Wed, 25 Aug 2010 23:25:29 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 Date: Thu, 26 Aug 2010 12:20:25 +0900 From: KAMEZAWA Hiroyuki To: David Rientjes Cc: KOSAKI Motohiro , LKML , linux-mm , Andrew Morton , Oleg Nesterov , Minchan Kim Subject: Re: [PATCH 1/2][BUGFIX] oom: remove totalpage normalization from oom_badness() Message-Id: <20100826122025.38112f79.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: References: <20100825184001.F3EF.A69D9226@jp.fujitsu.com> <20100826093923.d4ac29b6.kamezawa.hiroyu@jp.fujitsu.com> <20100826101139.eb05fe2d.kamezawa.hiroyu@jp.fujitsu.com> Organization: FUJITSU Co. LTD. X-Mailer: Sylpheed 3.0.3 (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: 3574 Lines: 95 On Wed, 25 Aug 2010 19:50:22 -0700 (PDT) David Rientjes wrote: > On Thu, 26 Aug 2010, KAMEZAWA Hiroyuki wrote: > > > Hmm. I'll add a text like following to cgroup/memory.txt. O.K. ? > > > > == > > Notes on oom_score and oom_score_adj. > > > > oom_score is calculated as > > oom_score = (taks's proportion of memory) + oom_score_adj. > > > > I'd replace "memory" with "memory limit (or memsw limit)" so it's clear > we're talking about the amount of memory available to task. > ok. > > Then, when you use oom_score_adj to control the order of priority of oom, > > you should know about the amount of memory you can use. > > Hmm, you need to know the amount of memory that you can use iff you know > the memcg limit and it's a static value. Otherwise, you only need to know > the "memory usage of your application relative to others in the same > cgroup." An oom_score_adj of +300 adds 30% of that memcg's limit to the > task, allowing all other tasks to use 30% more memory than that task with > it still be killed. An oom_score_adj of -300 allows that task to use 30% > more memory than other tasks without getting killed. These don't need to > know the actual limit. > Hmm. What's complicated is oom_score_adj's behavior. > > So, an approximate oom_score under memcg can be > > > > memcg_oom_score = (oom_score - oom_score_adj) * system_memory/memcg's limit > > + oom_score_adj. > > > > Right, that's the exact score within the memcg. > > But, I still wouldn't encourage a formula like this because the memcg > limit (or cpuset mems, mempolicy nodes, etc) are dynamic and may change > out from under us. So it's more important to define oom_score_adj in the > user's mind as a proportion of memory available to be added (either > positively or negatively) to its memory use when comparing it to other > tasks. The point is that the memcg limit isn't interesting in this > formula, it's more important to understand the priority of the task > _compared_ to other tasks memory usage in that memcg. > yes. For defineing/understanding priority, oom_score_adj is that. But it's priority isn't static. > It probably would be helpful, though, if you know that a vital system task > uses 1G, for instance, in a 4G memcg that an oom_score_adj of -250 will > disable oom killing for it. yes. > If that tasks leaks memory or becomes > significantly large, for whatever reason, it could be killed, but we _can_ > discount the 1G in comparison to other tasks as the "cost of doing > business" when it comes to vital system tasks: > > (memory usage) * (memory+swap limit / system memory) > yes. under 8G system, -250 will allow ingnoring 2G of usage. == How about this text ? == When you set a task's oom_score_adj, it can get priority not to be oom-killed. oom_score_adj gives priority proportional to the memory limitation. Assuming you set -250 to oom_score_adj. Under 4G memory limit, it gets 25% of bonus...1G memory bonus for avoiding OOM. Under 8G memory limit, it gets 25% of bonus...2G memory bonus for avoiding OOM. Then, what bonus a task can get depends on the context of OOM. If you use oom_score_adj and want to give bonus to a task, setting it in regard with minimum memory limitation which a task is under will work well. == Thanks, -Kame -- 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/