From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,T_DKIMWL_WL_HIGH autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 08B78C04AB5 for ; Thu, 6 Jun 2019 18:52:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D60012083D for ; Thu, 6 Jun 2019 18:52:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="k739h19W" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727537AbfFFSwi (ORCPT ); Thu, 6 Jun 2019 14:52:38 -0400 Received: from aserp2130.oracle.com ([141.146.126.79]:49696 "EHLO aserp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726893AbfFFSwi (ORCPT ); Thu, 6 Jun 2019 14:52:38 -0400 Received: from pps.filterd (aserp2130.oracle.com [127.0.0.1]) by aserp2130.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x56Imwel149579; Thu, 6 Jun 2019 18:51:28 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2018-07-02; bh=730DlizpPMBDP9JxaWPpPRW09tHdiXn9kT5XANcah2I=; b=k739h19WTHvvX2kUDtgH5cK/4SmGQoP0F6O2b7LmVCJzgJNm48MU9+dHLrEyHC0HMaaO Tj333O8KWgTGOBfoYirFbAkwzWwar5HkZQtqrs/dp8Nihdr7Dce0r9YXBaJ2iejS3QUb RQYrxRmF/zU/MnAOz0/RKJLFIn3euGg23QRWfsGR8c/4PtFvrK0+phfTXdhn3Y2iPMEP EDP9469GLrSLnUvIDYETs5SWlyQKLu7WOjJzvrb7iSa8438lT1qiANaDosjThhtTaNUK 71bV90GmtWx3WChWCSTP6djtBksev+KU+WbPFomQ+LJUAsXNet8EilC2XXRnx2QFpIjC yg== Received: from aserp3030.oracle.com (aserp3030.oracle.com [141.146.126.71]) by aserp2130.oracle.com with ESMTP id 2suevdtk1d-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 06 Jun 2019 18:51:28 +0000 Received: from pps.filterd (aserp3030.oracle.com [127.0.0.1]) by aserp3030.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x56Ioi2p069767; Thu, 6 Jun 2019 18:51:28 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by aserp3030.oracle.com with ESMTP id 2swnhcv15b-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 06 Jun 2019 18:51:27 +0000 Received: from abhmp0014.oracle.com (abhmp0014.oracle.com [141.146.116.20]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x56IpPQ6026659; Thu, 6 Jun 2019 18:51:26 GMT Received: from [10.175.215.95] (/10.175.215.95) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 06 Jun 2019 11:51:25 -0700 Subject: Re: [patch v2 3/3] cpuidle-haltpoll: disable host side polling when kvm virtualized To: Andrea Arcangeli Cc: Marcelo Tosatti , kvm-devel , Paolo Bonzini , Radim Krcmar , "Rafael J. Wysocki" , Peter Zijlstra , Wanpeng Li , Konrad Rzeszutek Wilk , Raslan KarimAllah , Boris Ostrovsky , Ankur Arora , Christian Borntraeger References: <20190603225242.289109849@amt.cnet> <20190603225254.360289262@amt.cnet> <20190604122404.GA18979@amt.cnet> <20190606183632.GA20928@redhat.com> From: Joao Martins Message-ID: <7f988399-7718-d4f4-f59c-792fbcbcf9b3@oracle.com> Date: Thu, 6 Jun 2019 19:51:21 +0100 MIME-Version: 1.0 In-Reply-To: <20190606183632.GA20928@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9280 signatures=668687 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=1 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=818 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906060127 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9280 signatures=668687 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=867 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906060127 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 6/6/19 7:36 PM, Andrea Arcangeli wrote: > Hello, > > On Thu, Jun 06, 2019 at 07:25:28PM +0100, Joao Martins wrote: >> But I wonder whether we should fail to load cpuidle-haltpoll when host halt >> polling can't be disabled[*]? That is to avoid polling in both host and guest >> and *possibly* avoid chances for performance regressions when running on older >> hypervisors? > > I don't think it's necessary: that would force an upgrade of the host > KVM version in order to use the guest haltpoll feature with an > upgraded guest kernel that can use the guest haltpoll. > Hence why I was suggesting a *guest* cpuidle-haltpoll module parameter to still allow it to load or otherwise (or allow guest to pick). > The guest haltpoll is self contained in the guest, so there's no > reason to prevent that by design or to force upgrade of the KVM host > version. It'd be more than enough to reload kvm.ko in the host with > the host haltpoll set to zero with the module parameter already > available, to achieve the same runtime without requiring a forced host > upgrade. > It's just with the new driver we unilaterally poll on both sides, just felt I would point it out should this raise unattended performance side effects ;) > The warning however sounds sensible. > Cool. Joao