From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757144AbXK3Wmn (ORCPT ); Fri, 30 Nov 2007 17:42:43 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752806AbXK3Wm2 (ORCPT ); Fri, 30 Nov 2007 17:42:28 -0500 Received: from mga09.intel.com ([134.134.136.24]:61089 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752768AbXK3Wm1 convert rfc822-to-8bit (ORCPT ); Fri, 30 Nov 2007 17:42:27 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.23,236,1194249600"; d="scan'208";a="219248780" X-MimeOLE: Produced By Microsoft Exchange V6.5 Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT Subject: RE: + restore-missing-sysfs-max_cstate-attr.patch added to -mm tree Date: Fri, 30 Nov 2007 14:37:46 -0800 Message-ID: <924EFEDD5F540B4284297C4DC59F3DEE2FAEAF@orsmsx423.amr.corp.intel.com> In-Reply-To: <20071130142058.816d1693.akpm@linux-foundation.org> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: + restore-missing-sysfs-max_cstate-attr.patch added to -mm tree Thread-Index: Acgzn5T8e8/KH4cCSgWNyjFp3ve8FAAAJW2Q References: <200711302153.lAULrZ7n026255@imap1.linux-foundation.org><924EFEDD5F540B4284297C4DC59F3DEE2FAE6A@orsmsx423.amr.corp.intel.com> <20071130142058.816d1693.akpm@linux-foundation.org> From: "Pallipadi, Venkatesh" To: "Andrew Morton" Cc: , , , , , , X-OriginalArrivalTime: 30 Nov 2007 22:37:30.0185 (UTC) FILETIME=[9756AB90:01C833A1] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org >On Fri, 30 Nov 2007 14:06:55 -0800 >"Pallipadi, Venkatesh" wrote: > >Please dont go off-list like this. I put Mark's original >mailing list cc's >back. Sorry for missing some cc's earlier. I blindly did a reply-all to the mm-commits mail I got. >> I will have to Nack this. The reason max_cstate was initentionally >> removed due to couple of reasons: > >It broke userspace without any warning or migration period, afaict. Yes. That's true. I will have to take the blame for that. It has been known for a while during cpuidle development. But, it was never documented as deprecating. >> 1) All in kernel users of max_cstate should rather be using >> pm_qos/latency interfaces. All such max_cstate usages must already be >> migrated. > >That code isn't merged. All kernel part is already merged. I mean, there are do drivers that depend on max_cstate. They use latency_notifier thing today and their migration to pm_qos part is not merged yet. >> 2) Supporting max_cstate as a dynamic parameter cleanly is no longer >> possible in acpi/processor_idle.c as the C-state policy has moved to >> cpuidle instead. It can be done if it is needed. But, just >below patch >> will not really work with cpuidle. >> >> Selecting max_cstate at boot time as a debug option still >works without >> this patch. >> >> So, just this patch will not get back the functionality with cpuidle. >> Infact changing it at run time will have no effect. Question >however is: >> Is there a real need to revive this parameter so that user can change >> max_cstate at run time? > >It is not known whether Mark is actually writing to this >thing. Perhaps >read-only permissions would be a suitable fix? > Exporting it as read only should be OK. We also need to know if there are hard user space dependency on writing to this from userspace. Thanks, Venki