From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f198.google.com (mail-pf0-f198.google.com [209.85.192.198]) by kanga.kvack.org (Postfix) with ESMTP id E84C66B000A for ; Fri, 6 Jul 2018 01:39:45 -0400 (EDT) Received: by mail-pf0-f198.google.com with SMTP id b17-v6so4953023pff.17 for ; Thu, 05 Jul 2018 22:39:45 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id j85-v6si8393011pfa.232.2018.07.05.22.39.44 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 05 Jul 2018 22:39:44 -0700 (PDT) Date: Fri, 6 Jul 2018 07:39:42 +0200 From: Michal Hocko Subject: Re: [PATCH] mm,oom: Bring OOM notifier callbacks to outside of OOM killer. Message-ID: <20180706053942.GF32658@dhcp22.suse.cz> References: <20180627143125.GW3593@linux.vnet.ibm.com> <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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180703160101.GC3593@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: "Paul E. McKenney" Cc: Tetsuo Handa , David Rientjes , linux-mm@kvack.org, Andrew Morton , linux-kernel@vger.kernel.org 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! -- Michal Hocko SUSE Labs