Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752498AbaLST4n (ORCPT ); Fri, 19 Dec 2014 14:56:43 -0500 Received: from www.linutronix.de ([62.245.132.108]:35745 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751316AbaLST4m (ORCPT ); Fri, 19 Dec 2014 14:56:42 -0500 Date: Fri, 19 Dec 2014 20:56:23 +0100 (CET) From: Thomas Gleixner To: Jacob Pan cc: "Pan, Jacob jun" , Preeti U Murthy , Peter Zijlstra , Viresh Kumar , LKP , LKML , "Zhang, Rui" , Frederic Weisbecker , Eduardo Valentin , "Van De Ven, Arjan" Subject: Re: [PATCH] tick/powerclamp: Remove tick_nohz_idle abuse In-Reply-To: <20141219103900.101f6c6d@jacob-VirtualBox> Message-ID: References: <54930EB1.9080309@linux.vnet.ibm.com> <20141218115239.53d17e39@jacob-VirtualBox> <20141219103900.101f6c6d@jacob-VirtualBox> User-Agent: Alpine 2.11 (DEB 23 2013-08-11) 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,URIBL_BLOCKED=0.001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 19 Dec 2014, Jacob Pan wrote: > On Thu, 18 Dec 2014 22:12:57 +0100 (CET) > Thomas Gleixner wrote: > > > On Thu, 18 Dec 2014, Jacob Pan wrote: > > > OK I agree, also as I mentioned earlier, Peter already has a patch > > > for consolidated idle loop and remove tick_nohz_idle_enter/exit > > > call from powerclamp driver. I have been working on a few tweaks to > > > maintain the functionality and efficiency with the consolidated > > > idle loop. We can apply the patches on top of yours. > > > > No. This is equally wrong as I pointed out before. The 'unified' idle > > loop is still fake and just pretending to be idle. > > > In terms of efficiency, the consolidated idle loop will allow turning > off sched tick during idle injection period. If we just take out the > tick_nohz_idle_xxx call, the effectiveness of powerclamp is going down > significantly. I am not arguing the design but from fixing regression > perspective or short term solution. There is no perspective. Period. Its violates every rightful assumption of the nohz_IDLE_* code and just ever worked by chance. There is so much subtle wreckage lurking there that the only sane solution is to forbid it. End of story. 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/