Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753471AbZG0FaK (ORCPT ); Mon, 27 Jul 2009 01:30:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752586AbZG0FaI (ORCPT ); Mon, 27 Jul 2009 01:30:08 -0400 Received: from mga07.intel.com ([143.182.124.22]:23979 "EHLO azsmga101.ch.intel.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752613AbZG0FaE (ORCPT ); Mon, 27 Jul 2009 01:30:04 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.43,274,1246863600"; d="scan'208";a="169171751" Subject: Dynamic configure max_cstate From: "Zhang, Yanmin" To: LKML , linux-acpi@vger.kernel.org Cc: yakui_zhao Content-Type: text/plain Date: Mon, 27 Jul 2009 13:30:13 +0800 Message-Id: <1248672613.2560.604.camel@ymzhang> Mime-Version: 1.0 X-Mailer: Evolution 2.22.1 (2.22.1-2.fc9) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 921 Lines: 24 When running a fio workload, I found sometimes cpu C state has big impact on the result. Mostly, fio is a disk I/O workload which doesn't spend much time with cpu, so cpu switch to C2/C3 freqently and the latency is big. If I start kernel with idle=poll or processor.max_cstate=1, the result is quite good. Consider a scenario that machine is busy at daytime and free at night. Could we add a dynamic configuration interface for processor.max_cstate or something similiar with sysfs? So user applications could change the max_cstate dynamically? For example, we could add a new parameter to function cpuidle_governor->select to mark the highest c state. Any idea? Yanmin -- 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/