From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) by kanga.kvack.org (Postfix) with ESMTP id 998F86B0003 for ; Fri, 6 Jul 2018 08:20:26 -0400 (EDT) Received: by mail-ed1-f72.google.com with SMTP id r9-v6so4266964edo.16 for ; Fri, 06 Jul 2018 05:20:26 -0700 (PDT) Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com. [148.163.158.5]) by mx.google.com with ESMTPS id 47-v6si4883829edz.8.2018.07.06.05.20.24 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 06 Jul 2018 05:20:24 -0700 (PDT) Received: from pps.filterd (m0098421.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w66CE8rP126461 for ; Fri, 6 Jul 2018 08:20:23 -0400 Received: from e12.ny.us.ibm.com (e12.ny.us.ibm.com [129.33.205.202]) by mx0a-001b2d01.pphosted.com with ESMTP id 2k26r5kya5-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Fri, 06 Jul 2018 08:20:23 -0400 Received: from localhost by e12.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 6 Jul 2018 08:20:22 -0400 Date: Fri, 6 Jul 2018 05:22:36 -0700 From: "Paul E. McKenney" Subject: Re: [PATCH] mm,oom: Bring OOM notifier callbacks to outside of OOM killer. Reply-To: paulmck@linux.vnet.ibm.com References: <20180628113942.GD32348@dhcp22.suse.cz> <20180628213105.GP3593@linux.vnet.ibm.com> <20180629090419.GD13860@dhcp22.suse.cz> <20180629125218.GX3593@linux.vnet.ibm.com> <20180629132638.GD5963@dhcp22.suse.cz> <20180630170522.GZ3593@linux.vnet.ibm.com> <20180702213714.GA7604@linux.vnet.ibm.com> <20180703072413.GD16767@dhcp22.suse.cz> <20180703160101.GC3593@linux.vnet.ibm.com> <20180706053942.GF32658@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180706053942.GF32658@dhcp22.suse.cz> Message-Id: <20180706122236.GB3593@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Tetsuo Handa , David Rientjes , linux-mm@kvack.org, Andrew Morton , linux-kernel@vger.kernel.org On Fri, Jul 06, 2018 at 07:39:42AM +0200, Michal Hocko wrote: > On Tue 03-07-18 09:01:01, Paul E. McKenney wrote: > > On Tue, Jul 03, 2018 at 09:24:13AM +0200, Michal Hocko wrote: > > > On Mon 02-07-18 14:37:14, Paul E. McKenney wrote: > > > [...] > > > > commit d2b8d16b97ac2859919713b2d98b8a3ad22943a2 > > > > Author: Paul E. McKenney > > > > Date: Mon Jul 2 14:30:37 2018 -0700 > > > > > > > > rcu: Remove OOM code > > > > > > > > There is reason to believe that RCU's OOM code isn't really helping > > > > that much, given that the best it can hope to do is accelerate invoking > > > > callbacks by a few seconds, and even then only if some CPUs have no > > > > non-lazy callbacks, a condition that has been observed to be rare. > > > > This commit therefore removes RCU's OOM code. If this causes problems, > > > > it can easily be reinserted. > > > > > > > > Reported-by: Michal Hocko > > > > Reported-by: Tetsuo Handa > > > > Signed-off-by: Paul E. McKenney > > > > > > I would also note that waiting in the notifier might be a problem on its > > > own because we are holding the oom_lock and the system cannot trigger > > > the OOM killer while we are holding it and waiting for oom_callback_wq > > > event. I am not familiar with the code to tell whether this can deadlock > > > but from a quick glance I _suspect_ that we might depend on __rcu_reclaim > > > and basically an arbitrary callback so no good. > > > > > > Acked-by: Michal Hocko > > > > > > Thanks! > > > > Like this? > > Thanks! Very good, queued for the merge window after next, that is, whatever number after v4.19. ;-) Thanx, Paul