From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754411AbaFTTEz (ORCPT ); Fri, 20 Jun 2014 15:04:55 -0400 Received: from relay4-d.mail.gandi.net ([217.70.183.196]:34232 "EHLO relay4-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754090AbaFTTEm (ORCPT ); Fri, 20 Jun 2014 15:04:42 -0400 Date: Fri, 20 Jun 2014 12:04:34 -0700 From: josh@joshtriplett.org To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, sbw@mit.edu Subject: Re: [PATCH tip/core/rcu 0/5] Fix for cond_resched performance regression Message-ID: <20140620190434.GA22178@cloud> References: <20140620183249.GA6325@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140620183249.GA6325@linux.vnet.ibm.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 20, 2014 at 11:32:49AM -0700, Paul E. McKenney wrote: > Hello! > > This series contains changes to address the performance regressions > introduced by commit ac1bea85781e (Make cond_resched() report RCU > quiescent states), which was in turn fixing a problem where tasks looping > in the kernel could delay RCU grace periods. The changes in this series > are as follows: > > 1. Reduce the overhead of checking added to cond_resched() and friends. > > 2. Add a new cond_resched_rcu_qs() to provide RCU quiescent states > even if cond_resched() should stop doing so. > > 3. Add a new RCU_COND_RESCHED_QS to prevent cond_resched() from > reporting RCU quiescent states. > > 4. Prevent rcutorture testing from reporting spurious RCU CPU stall > warnings, and also to test RCU_COND_RESCHED_QS. > > 5. Provides a boot/sysfs rcutree.jiffies_till_cond_resched_qs > parameter to replace the magic "7". For all five patches: Reviewed-by: Josh Triplett Glad to see this doesn't add any overhead to rcutiny. - Josh Triplett