From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756296Ab1E3V2k (ORCPT ); Mon, 30 May 2011 17:28:40 -0400 Received: from e7.ny.us.ibm.com ([32.97.182.137]:53328 "EHLO e7.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751938Ab1E3V2j (ORCPT ); Mon, 30 May 2011 17:28:39 -0400 Date: Mon, 30 May 2011 14:28:33 -0700 From: "Paul E. McKenney" To: Peter Zijlstra Cc: Damien Wyart , Ingo Molnar , Mike Galbraith , linux-kernel@vger.kernel.org Subject: Re: Very high CPU load when idle with 3.0-rc1 Message-ID: <20110530212833.GS2668@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20110530055924.GA9169@brouette> <1306755291.1200.2872.camel@twins> <20110530162354.GQ2668@linux.vnet.ibm.com> <1306775989.2497.527.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1306775989.2497.527.camel@laptop> 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 Mon, May 30, 2011 at 07:19:49PM +0200, Peter Zijlstra wrote: > On Mon, 2011-05-30 at 09:23 -0700, Paul E. McKenney wrote: > > sp.sched_priority = RCU_KTHREAD_PRIO; > > sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); > > Why are those things RT tasks anyway? The old ksoftirq runs as a regular > task. And once you start boosting things you can boost this into FIFO as > well... > > just wondering.. Because priority boosting doesn't help unless the callbacks also run RT priority. I could make it so that they ran as normal tasks if !RCU_BOOST, but they would still need to run as RT tasks for RCU_BOOST. I figured running them the same way in both cases would be simpler. Thanx, Paul