From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966844AbaFTSc5 (ORCPT ); Fri, 20 Jun 2014 14:32:57 -0400 Received: from e38.co.us.ibm.com ([32.97.110.159]:57956 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S966270AbaFTSc4 (ORCPT ); Fri, 20 Jun 2014 14:32:56 -0400 Date: Fri, 20 Jun 2014 11:32:49 -0700 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, 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: [PATCH tip/core/rcu 0/5] Fix for cond_resched performance regression Message-ID: <20140620183249.GA6325@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14062018-1344-0000-0000-00000253DB0E Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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". Thanx, Paul ------------------------------------------------------------------------ b/Documentation/kernel-parameters.txt | 7 + b/fs/file.c | 2 b/include/linux/rcupdate.h | 35 ----- b/include/linux/rcutiny.h | 17 ++ b/include/linux/rcutree.h | 44 ++++++ b/init/Kconfig | 26 +++ b/kernel/rcu/rcutorture.c | 4 b/kernel/rcu/tree.c | 111 +++++++++++++--- b/kernel/rcu/tree.h | 6 b/kernel/rcu/tree_plugin.h | 4 b/kernel/rcu/update.c | 18 -- b/mm/mlock.c | 2 b/tools/testing/selftests/rcutorture/configs/rcu/TREE01 | 1 13 files changed, 201 insertions(+), 76 deletions(-)