From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755208Ab0IHO23 (ORCPT ); Wed, 8 Sep 2010 10:28:29 -0400 Received: from cantor2.suse.de ([195.135.220.15]:48242 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751323Ab0IHO21 (ORCPT ); Wed, 8 Sep 2010 10:28:27 -0400 Date: Wed, 8 Sep 2010 16:28:26 +0200 From: Jan Blunck To: Peter Zijlstra Cc: Linux-Kernel Mailinglist , linux-rt-users@vger.kernel.org, Sven-Thorsten Dietrich , Michael Galbraith Subject: Re: [RFC 3/4] Disable scheduler tick when we are running SCHED_FIFO tasks Message-ID: <20100908142826.GI7436@bolzano.suse.de> References: <1283948964-6418-1-git-send-email-jblunck@suse.de> <1283948964-6418-4-git-send-email-jblunck@suse.de> <1283949943.23762.16.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1283949943.23762.16.camel@laptop> Organization: SUSE LINUX Products GmbH, GF Markus Rex, HRB 16746 (AG Nuernberg) User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 08, Peter Zijlstra wrote: > On Wed, 2010-09-08 at 14:29 +0200, Jan Blunck wrote: > > This patch is disabling the scheduler tick to go off when there is a task > > with SCHED_FIFO policy running. Since these tasks are not timesliced anyway > > we only care about timers, softirqs and such stuff just like when we disable > > the tick during idle periods. > > > > Also, doesn't this break any and all jiffies users? > Sure. It was enough to make FTQ run. > And you need to restart the tick on call_rcu() and everything else that > requires the tick for processing. > I realized that before as well but somehow forgot about it. Checking for a disabled timer tick on syscall entry would help. Like we do on irq entry as well. Jan