From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f197.google.com (mail-wr0-f197.google.com [209.85.128.197]) by kanga.kvack.org (Postfix) with ESMTP id 3C3AB6B0005 for ; Wed, 4 Apr 2018 02:23:43 -0400 (EDT) Received: by mail-wr0-f197.google.com with SMTP id v11so10697173wri.13 for ; Tue, 03 Apr 2018 23:23:43 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id z12si3356675wmh.127.2018.04.03.23.23.41 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 03 Apr 2018 23:23:41 -0700 (PDT) Date: Wed, 4 Apr 2018 08:23:40 +0200 From: Michal Hocko Subject: Re: [PATCH v1] kernel/trace:check the val against the available mem Message-ID: <20180404062340.GD6312@dhcp22.suse.cz> References: <1522320104-6573-1-git-send-email-zhaoyang.huang@spreadtrum.com> <20180330102038.2378925b@gandalf.local.home> <20180403110612.GM5501@dhcp22.suse.cz> <20180403075158.0c0a2795@gandalf.local.home> <20180403121614.GV5501@dhcp22.suse.cz> <20180403082348.28cd3c1c@gandalf.local.home> <20180403123514.GX5501@dhcp22.suse.cz> <20180403093245.43e7e77c@gandalf.local.home> <20180403135607.GC5501@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Zhaoyang Huang Cc: Steven Rostedt , Ingo Molnar , linux-kernel@vger.kernel.org, kernel-patch-test@lists.linaro.org, Andrew Morton , Joel Fernandes , linux-mm@kvack.org, Vlastimil Babka On Wed 04-04-18 10:58:39, Zhaoyang Huang wrote: > On Tue, Apr 3, 2018 at 9:56 PM, Michal Hocko wrote: > > On Tue 03-04-18 09:32:45, Steven Rostedt wrote: > >> On Tue, 3 Apr 2018 14:35:14 +0200 > >> Michal Hocko wrote: > > [...] > >> > Being clever is OK if it doesn't add a tricky code. And relying on > >> > si_mem_available is definitely tricky and obscure. > >> > >> Can we get the mm subsystem to provide a better method to know if an > >> allocation will possibly succeed or not before trying it? It doesn't > >> have to be free of races. Just "if I allocate this many pages right > >> now, will it work?" If that changes from the time it asks to the time > >> it allocates, that's fine. I'm not trying to prevent OOM to never > >> trigger. I just don't want to to trigger consistently. > > > > How do you do that without an actuall allocation request? And more > > fundamentally, what if your _particular_ request is just fine but it > > will get us so close to the OOM edge that the next legit allocation > > request simply goes OOM? There is simply no sane interface I can think > > of that would satisfy a safe/sensible "will it cause OOM" semantic. > > > The point is the app which try to allocate the size over the line will escape > the OOM and let other innocent to be sacrificed. However, the one which you > mentioned above will be possibly selected by OOM that triggered by consequnce > failed allocation. If you are afraid of that then you can have a look at {set,clear}_current_oom_origin() which will automatically select the current process as an oom victim and kill it. -- Michal Hocko SUSE Labs