Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752715AbaJTHk6 (ORCPT ); Mon, 20 Oct 2014 03:40:58 -0400 Received: from mx0b-0016f401.pphosted.com ([67.231.156.173]:34844 "EHLO mx0b-0016f401.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751493AbaJTHk5 (ORCPT ); Mon, 20 Oct 2014 03:40:57 -0400 From: Neil Zhang To: Greg KH CC: "linux-kernel@vger.kernel.org" Date: Mon, 20 Oct 2014 00:40:48 -0700 Subject: RE: [PATCH] drivers: base: update cpu offline info when do hotplug Thread-Topic: [PATCH] drivers: base: update cpu offline info when do hotplug Thread-Index: Ac/sMgXhFfe7zufuRMiLPJjsVwlNVAABMN5A Message-ID: <9034CBD80F070943B59700D7F8149ED9024EB81CC6@SC-VEXCH4.marvell.com> References: <1413775748-22478-1-git-send-email-zhangwm@marvell.com> <20141020044340.GA9589@kroah.com> <9034CBD80F070943B59700D7F8149ED9024EB81CAF@SC-VEXCH4.marvell.com> <20141020064826.GA4064@kroah.com> In-Reply-To: <20141020064826.GA4064@kroah.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: text/plain; charset="gb2312" MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:5.12.52,1.0.28,0.0.0000 definitions=2014-10-19_03:2014-10-17,2014-10-19,1970-01-01 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=7.0.1-1402240000 definitions=main-1410200082 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by nfs id s9K7fAmf022796 Greg, -----Original Message----- From: Greg KH [mailto:gregkh@linuxfoundation.org] Sent: 2014??10??20?? 14:48 To: Neil Zhang Cc: linux-kernel@vger.kernel.org Subject: Re: [PATCH] drivers: base: update cpu offline info when do hotplug On Sun, Oct 19, 2014 at 11:39:23PM -0700, Neil Zhang wrote: >> How much noise is this going to cause on a big/little system that >> constantly hot unplug/plugs processors all of the time? > > Can you explain more what kind of noise will be introduced on a big/little system? Have you tested this on such a machine? I didn't have such kind of machine on hand. Can anyone has such machine to verify it? Thanks! > As I know IKS on arm will use cpu_suspend way to power down a core. Are you sure that it also doesn't use that same functionality to drop a processor to save power? As I know it use cpu_suspend to switch out a processor in IKS and there is no cpu hotplug notifier in this procedure. Why do you need/want this notification? What are you going to do with this information that you don't already have? The offline won't be updated if an in kernel hotplug governor plug in / out a core which cause the sysfs interface report a wrong status. thanks, greg k-h Best Regards, Neil Zhang ????{.n?+???????+%?????ݶ??w??{.n?+????{??G?????{ay?ʇڙ?,j??f???h?????????z_??(?階?ݢj"???m??????G????????????&???~???iO???z??v?^?m???? ????????I?