From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756993Ab2CBWXH (ORCPT ); Fri, 2 Mar 2012 17:23:07 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:38057 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754826Ab2CBWXG (ORCPT ); Fri, 2 Mar 2012 17:23:06 -0500 Date: Fri, 2 Mar 2012 14:23:03 -0800 From: Andrew Morton To: yanmin_zhang@linux.intel.com Cc: "linux-kernel@vger.kernel.org" , "Brown, Len" , "Liu, ShuoX" , Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" Subject: Re: Subject: [PATCH] cpuidle: Add a sysfs entry to disable specific C state for debug purpose. Message-Id: <20120302142303.648285a7.akpm@linux-foundation.org> In-Reply-To: <1330647453.1916.7.camel@ymzhang> References: <1330647453.1916.7.camel@ymzhang> X-Mailer: Sylpheed 3.0.2 (GTK+ 2.20.1; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 02 Mar 2012 08:17:33 +0800 Yanmin Zhang wrote: > On Wed, 2012-02-29 at 04:55 +0000, Liu, ShuoX wrote: > > From: ShuoX Liu > > > > Some C states of new CPU might be not good. One reason is BIOS might configure > > them incorrectly. To help developers root cause it quickly, the patch adds a > > new sysfs entry, so developers could disable specific C state manually. > > > > In addition, C state might have much impact on performance tuning, as it takes > > much time to enter/exit C states, which might delay interrupt processing. With > > the new debug option, developers could check if a deep C state could impact > > performance and how much impact it could cause. > > > > Signed-off-by: ShuoX Liu > Andrew, > > Would you like to merge the patch into your testing tree? I can do that, but it's hardly my area and I can't comment on the desirability of the patch and Len is having quiet time. Perhaps the x86 guys can take a look please> > It's useful to help developers debug some issues. It would help developers more if it was documented a bit. As it stands, they'd be lucky if they even knew it existed. Looky: akpm:/usr/src/linux-3.3-rc5> grep -ril cpuidle Documentation Documentation/trace/events-power.txt Documentation/ABI/testing/sysfs-devices-system-cpu Documentation/kernel-parameters.txt Documentation/00-INDEX Documentation/cpuidle/core.txt Documentation/cpuidle/sysfs.txt Documentation/cpuidle/driver.txt Documentation/cpuidle/governor.txt