From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yh0-f49.google.com (mail-yh0-f49.google.com [209.85.213.49]) by kanga.kvack.org (Postfix) with ESMTP id 9AFB76B0031 for ; Wed, 15 Jan 2014 19:18:51 -0500 (EST) Received: by mail-yh0-f49.google.com with SMTP id b6so744464yha.8 for ; Wed, 15 Jan 2014 16:18:51 -0800 (PST) Received: from mail-yh0-x231.google.com (mail-yh0-x231.google.com [2607:f8b0:4002:c01::231]) by mx.google.com with ESMTPS id q69si7267911yhd.195.2014.01.15.16.18.50 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 15 Jan 2014 16:18:50 -0800 (PST) Received: by mail-yh0-f49.google.com with SMTP id b6so746849yha.36 for ; Wed, 15 Jan 2014 16:18:50 -0800 (PST) Date: Wed, 15 Jan 2014 16:18:47 -0800 (PST) From: David Rientjes Subject: Re: [patch] mm: oom_kill: revert 3% system memory bonus for privileged tasks In-Reply-To: <20140115234308.GB4407@cmpxchg.org> Message-ID: References: <20140115234308.GB4407@cmpxchg.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Johannes Weiner Cc: Andrew Morton , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Wed, 15 Jan 2014, Johannes Weiner wrote: > With a63d83f427fb ("oom: badness heuristic rewrite"), the OOM killer > tries to avoid killing privileged tasks by subtracting 3% of overall > memory (system or cgroup) from their per-task consumption. But as a > result, all root tasks that consume less than 3% of overall memory are > considered equal, and so it only takes 33+ privileged tasks pushing > the system out of memory for the OOM killer to do something stupid and > kill sshd or dhclient. For example, on a 32G machine it can't tell > the difference between the 1M agetty and the 10G fork bomb member. > > The changelog describes this 3% boost as the equivalent to the global > overcommit limit being 3% higher for privileged tasks, but this is not > the same as discounting 3% of overall memory from _every privileged > task individually_ during OOM selection. > > Revert back to the old priority boost of pretending root tasks are > only a quarter of their actual size. > Unfortunately, I think this could potentially be too much of a bonus. On your same 32GB machine, if a root process is using 18GB and a user process is using 14GB, the user process ends up getting selected while the current discount of 3% still selects the root process. I do like the idea of scaling this bonus depending on points, however. I think it would be better if we could scale the discount but also limit it to some sane value. -- 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