From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f197.google.com (mail-io0-f197.google.com [209.85.223.197]) by kanga.kvack.org (Postfix) with ESMTP id 17A0B280254 for ; Thu, 1 Dec 2016 11:36:19 -0500 (EST) Received: by mail-io0-f197.google.com with SMTP id r94so20738651ioe.7 for ; Thu, 01 Dec 2016 08:36:19 -0800 (PST) Received: from merlin.infradead.org (merlin.infradead.org. [2001:4978:20e::2]) by mx.google.com with ESMTPS id u125si9767051itd.17.2016.12.01.08.36.18 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 01 Dec 2016 08:36:18 -0800 (PST) Date: Thu, 1 Dec 2016 17:36:14 +0100 From: Peter Zijlstra Subject: Re: INFO: rcu_sched detected stalls on CPUs/tasks with `kswapd` and `mem_cgroup_shrink_node` Message-ID: <20161201163614.GL3092@twins.programming.kicks-ass.net> References: <20161130110944.GD18432@dhcp22.suse.cz> <20161130115320.GO3924@linux.vnet.ibm.com> <20161130131910.GF18432@dhcp22.suse.cz> <20161130142955.GS3924@linux.vnet.ibm.com> <20161130163820.GQ3092@twins.programming.kicks-ass.net> <20161130170557.GK18432@dhcp22.suse.cz> <20161130175015.GR3092@twins.programming.kicks-ass.net> <20161130194019.GF3924@linux.vnet.ibm.com> <20161201053035.GC3092@twins.programming.kicks-ass.net> <20161201124024.GB3924@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161201124024.GB3924@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: "Paul E. McKenney" Cc: Michal Hocko , Donald Buczek , Paul Menzel , dvteam@molgen.mpg.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Josh Triplett On Thu, Dec 01, 2016 at 04:40:24AM -0800, Paul E. McKenney wrote: > On Thu, Dec 01, 2016 at 06:30:35AM +0100, Peter Zijlstra wrote: > > Sure, we all dislike IPIs, but I'm thinking this half-way point is > > sensible, no point in issuing user visible annoyance if indeed we can > > prod things back to life, no? > > > > Only if we utterly fail to make it respond should we bug the user with > > our failure.. > > Sold! ;-) > > I will put together a patch later today. > > My intent is to hold off on the "upgrade cond_resched()" patch, one > step at a time. Longer term, I do very much like the idea of having > cond_resched() do both scheduling and RCU quiescent states, assuming > that this avoids performance pitfalls. Well, with the above change cond_resched() is already sufficient, no? In fact, by doing the IPI thing we get the entire cond_resched*() family, and we could add the should_resched() guard to cond_resched_rcu(). -- 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