Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752028Ab0LUN5N (ORCPT ); Tue, 21 Dec 2010 08:57:13 -0500 Received: from mx1.redhat.com ([209.132.183.28]:38645 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751928Ab0LUN5M (ORCPT ); Tue, 21 Dec 2010 08:57:12 -0500 Message-ID: <4D10B214.8010305@redhat.com> Date: Tue, 21 Dec 2010 15:56:36 +0200 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.13) Gecko/20101209 Fedora/3.1.7-0.35.b3pre.fc14 Lightning/1.0b3pre Thunderbird/3.1.7 MIME-Version: 1.0 To: Frederic Weisbecker CC: Steven Rostedt , LKML , Thomas Gleixner , Peter Zijlstra , "Paul E . McKenney" , Lai Jiangshan , Andrew Morton , Anton Blanchard , Tim Pepper Subject: Re: [RFC PATCH 00/15] Nohz task support References: <1292858662-5650-1-git-send-email-fweisbec@gmail.com> <1292859886.22905.22.camel@gandalf.stny.rr.com> <20101220233341.GA1715@nowhere> In-Reply-To: <20101220233341.GA1715@nowhere> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1481 Lines: 37 On 12/21/2010 01:33 AM, Frederic Weisbecker wrote: > On Mon, Dec 20, 2010 at 10:44:46AM -0500, Steven Rostedt wrote: > > On Mon, 2010-12-20 at 16:24 +0100, Frederic Weisbecker wrote: > > > The timer interrupt handles several things like preemption, > > > timekeeping, rcu, etc... > > > > > > However it appears that sometimes it is simply useless like > > > when a task runs alone and even more when it is in userspace > > > as RCU doesn't need it at all in such case. > > > > > > It appears that HPC workload would get some win of such timer > > > deactivation, and perhaps also the Real Time world as this > > > minimizes the critical sections due to way less interrupts to > > > handle. > > > > > > It works through the procfs interface: > > > > > > echo 1> /proc/self/nohz > > > > I wounder if we could just have this happen automatically. > > But this would add some global overhead, especially in the syscall > path as we need to take the slow path to hook userspace resume/exit. This is zero as there is already a test on thread_info->flags on the syscall exit path. (or I misunderstood you - what's the purpose of the slow path?) -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/