Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932074Ab2FNQUo (ORCPT ); Thu, 14 Jun 2012 12:20:44 -0400 Received: from www.linutronix.de ([62.245.132.108]:58860 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756403Ab2FNQUm (ORCPT ); Thu, 14 Jun 2012 12:20:42 -0400 Date: Thu, 14 Jun 2012 18:20:39 +0200 (CEST) From: Thomas Gleixner To: "Paul E. McKenney" cc: Peter Zijlstra , LKML , Ingo Molnar , "Srivatsa S. Bhat" , Rusty Russell , Tejun Heo Subject: Re: [RFC patch 2/5] smpboot: Provide infrastructure for percpu hotplug threads In-Reply-To: <20120614154556.GD2458@linux.vnet.ibm.com> Message-ID: References: <20120613185748.GF2427@linux.vnet.ibm.com> <20120613191745.GG2427@linux.vnet.ibm.com> <20120613204725.GA9858@linux.vnet.ibm.com> <20120614045125.GA30257@linux.vnet.ibm.com> <20120614125939.GC2443@linux.vnet.ibm.com> <1339678887.2559.30.camel@twins> <20120614144734.GA2458@linux.vnet.ibm.com> <1339685789.2559.37.camel@twins> <20120614154556.GD2458@linux.vnet.ibm.com> User-Agent: Alpine 2.02 (LFD 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1255 Lines: 33 On Thu, 14 Jun 2012, Paul E. McKenney wrote: > On Thu, Jun 14, 2012 at 04:56:29PM +0200, Peter Zijlstra wrote: > > On Thu, 2012-06-14 at 07:47 -0700, Paul E. McKenney wrote: > > > RCU callback processing consumes the entire CPU in RCU_BOOST case where > > > processing runs at real-time priority. This is analogous to RT throttling > > > in the scheduler. > > > > But previously we can in non-preemptible softirq context, why would if > > behave differently when done from a RT task? > > In -rt, yes, but in mainline, ksoftirqd does not run at RT prio, right? > > > Also, no its not quite like the throttling, that really idles the cpu > > even if there's no SCHED_OTHER tasks to run. > > Agreed, not -exactly- like throttling, but it has a broadly similar > goal, namely to prevent a given type of processing from starving > everything else in the system. > > That said, why does throttling idle the CPU even if there is no other > SCHED_OTHER tasks to run? For simplicity reasons :) Thanks, tglx -- 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/