From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932592AbcE3HHK (ORCPT ); Mon, 30 May 2016 03:07:10 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:34727 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753779AbcE3HHI (ORCPT ); Mon, 30 May 2016 03:07:08 -0400 Date: Mon, 30 May 2016 09:07:05 +0200 From: Michal Hocko To: Vladimir Davydov Cc: linux-mm@kvack.org, Tetsuo Handa , David Rientjes , Oleg Nesterov , Andrew Morton , LKML Subject: Re: [PATCH 3/6] mm, oom_adj: make sure processes sharing mm have same view of oom_score_adj Message-ID: <20160530070705.GD22928@dhcp22.suse.cz> References: <1464266415-15558-1-git-send-email-mhocko@kernel.org> <1464266415-15558-4-git-send-email-mhocko@kernel.org> <20160527111803.GG27686@dhcp22.suse.cz> <20160527161821.GE26059@esperanza> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160527161821.GE26059@esperanza> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 27-05-16 19:18:21, Vladimir Davydov wrote: > On Fri, May 27, 2016 at 01:18:03PM +0200, Michal Hocko wrote: > ... > > @@ -1087,7 +1105,25 @@ static int __set_oom_adj(struct file *file, int oom_adj, bool legacy) > > unlock_task_sighand(task, &flags); > > err_put_task: > > put_task_struct(task); > > + > > + if (mm) { > > + struct task_struct *p; > > + > > + rcu_read_lock(); > > + for_each_process(p) { > > + task_lock(p); > > + if (!p->vfork_done && process_shares_mm(p, mm)) { > > + p->signal->oom_score_adj = oom_adj; > > + if (!legacy && has_capability_noaudit(current, CAP_SYS_RESOURCE)) > > + p->signal->oom_score_adj_min = (short)oom_adj; > > + } > > + task_unlock(p); > > I.e. you write to /proc/pid1/oom_score_adj and get > /proc/pid2/oom_score_adj updated if pid1 and pid2 share mm? > IMO that looks unexpected from userspace pov. How much different it is from threads in the same thread group? Processes sharing the mm without signals is a rather weird threading model isn't it? Currently we just lie to users about their oom_score_adj in this weird corner case. The only exception was OOM_SCORE_ADJ_MIN where we really didn't kill the task but all other values are simply ignored in practice. > May be, we'd better add mm->oom_score_adj and set it to the min > signal->oom_score_adj over all processes sharing it? This would > require iterating over all processes every time oom_score_adj gets > updated, but that's a slow path. Not sure I understand. So you would prefer that mm->oom_score_adj might disagree with p->signal->oom_score_adj? -- Michal Hocko SUSE Labs