From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id DCCEB6B0047 for ; Thu, 11 Feb 2010 16:43:51 -0500 (EST) Date: Thu, 11 Feb 2010 13:43:43 -0800 From: Andrew Morton Subject: Re: [patch 4/7 -mm] oom: badness heuristic rewrite Message-Id: <20100211134343.4886499c.akpm@linux-foundation.org> In-Reply-To: References: <4B73833D.5070008@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: David Rientjes Cc: Rik van Riel , KAMEZAWA Hiroyuki , Nick Piggin , Andrea Arcangeli , Balbir Singh , Lubos Lunak , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Thu, 11 Feb 2010 01:14:43 -0800 (PST) David Rientjes wrote: > On Wed, 10 Feb 2010, Rik van Riel wrote: > > > > OOM_ADJUST_MIN and OOM_ADJUST_MAX have been exported to userspace since > > > 2006 via include/linux/oom.h. This alters their values from -16 to -1000 > > > and from +15 to +1000, respectively. > > > > That seems like a bad idea. Google may have the luxury of > > being able to recompile all its in-house applications, but > > this will not be true for many other users of /proc//oom_adj > > > > Changing any value that may have a tendency to be hardcoded elsewhere is > always controversial, but I think the nature of /proc/pid/oom_adj allows > us to do so for two specific reasons: > > - hardcoded values tend not the fall within a range, they tend to either > always prefer a certain task for oom kill first or disable oom killing > entirely. The current implementation uses this as a bitshift on a > seemingly unpredictable and unscientific heuristic that is very > difficult to predict at runtime. This means that fewer and fewer > applications would hardcode a value of '8', for example, because its > semantics depends entirely on RAM capacity of the system to begin with > since badness() scores are only useful when used in comparison with > other tasks. You'd be amazed what dumb things applications do. Get thee to http://google.com/codesearch?hl=en&lr=&q=[^a-z]oom_adj[^a-z]&sbtn=Search and start reading. All 641 matches ;) Here's one which which writes -16: http://google.com/codesearch/p?hl=en#eN5TNOm7KtI/trunk/wlan/vendor/asus/eeepc/init.rc&q=[^a-z]oom_adj[^a-z]&sa=N&cd=70&ct=rc Let's not change the ABI please. -- 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