From mboxrd@z Thu Jan 1 00:00:00 1970 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: multipart/mixed; boundary="===============7681022228689903251==" MIME-Version: 1.0 From: Thomas Gleixner To: lkp@lists.01.org Subject: Re: [PATCH] tick/powerclamp: Remove tick_nohz_idle abuse Date: Fri, 19 Dec 2014 20:56:23 +0100 Message-ID: In-Reply-To: <20141219103900.101f6c6d@jacob-VirtualBox> List-Id: --===============7681022228689903251== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable 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 --===============7681022228689903251==--