From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752602AbaANEO7 (ORCPT ); Mon, 13 Jan 2014 23:14:59 -0500 Received: from e33.co.us.ibm.com ([32.97.110.151]:37837 "EHLO e33.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752173AbaANEO4 (ORCPT ); Mon, 13 Jan 2014 23:14:56 -0500 Date: Mon, 13 Jan 2014 20:14:50 -0800 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, darren@dvhart.com, fweisbec@gmail.com, oleg@redhat.com, sbw@mit.edu Subject: [PATCH tip/core/rcu 0/3] Crude timer-wheel latency hacks Message-ID: <20140114041449.GA13934@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: 14011404-0928-0000-0000-000005603982 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello! The following three patches provide some crude timer-wheel latency patches. I understand that a more comprehensive solution is in progress, but in the meantime, these patches work well in cases where a given CPU has either zero or one timers pending, which is a common case for NO_HZ_FULL kernels. So, on the off-chance that this is helpful to someone, the individual patches are as follows: 1. Avoid jiffy-at-a-time stepping when the timer wheel is empty. 2. Avoid jiffy-at-a-time stepping when the timer wheel transitions to empty. 3. Avoid jiffy-at-a-time stepping after a timer is added to an initially empty timer wheel. Thanx, Paul ------------------------------------------------------------------------ b/kernel/timer.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+)