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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 3CF10C433FF for ; Sat, 3 Aug 2019 20:21:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 067782073D for ; Sat, 3 Aug 2019 20:21:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728958AbfHCUVg (ORCPT ); Sat, 3 Aug 2019 16:21:36 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54994 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728906AbfHCUVg (ORCPT ); Sat, 3 Aug 2019 16:21:36 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B8EC0A4D31; Sat, 3 Aug 2019 20:21:35 +0000 (UTC) Received: from amt.cnet (ovpn-112-2.gru2.redhat.com [10.97.112.2]) by smtp.corp.redhat.com (Postfix) with ESMTP id 17FC25C22B; Sat, 3 Aug 2019 20:21:35 +0000 (UTC) Received: from amt.cnet (localhost [127.0.0.1]) by amt.cnet (Postfix) with ESMTP id C4ED6105135; Sat, 3 Aug 2019 17:21:05 -0300 (BRT) Received: (from marcelo@localhost) by amt.cnet (8.14.7/8.14.7/Submit) id x73KL24Q009531; Sat, 3 Aug 2019 17:21:02 -0300 Date: Sat, 3 Aug 2019 17:21:01 -0300 From: Marcelo Tosatti To: Paolo Bonzini Cc: "Rafael J. Wysocki" , Wanpeng Li , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Radim =?utf-8?B?S3LEjW3DocWZ?= , Linux PM Subject: Re: [PATCH] cpuidle-haltpoll: Enable kvm guest polling when dedicated physical CPUs are available Message-ID: <20190803202058.GA9316@amt.cnet> References: <1564643196-7797-1-git-send-email-wanpengli@tencent.com> <7b1e3025-f513-7068-32ac-4830d67b65ac@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Sat, 03 Aug 2019 20:21:35 +0000 (UTC) Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On Thu, Aug 01, 2019 at 06:54:49PM +0200, Paolo Bonzini wrote: > On 01/08/19 18:51, Rafael J. Wysocki wrote: > > On 8/1/2019 9:06 AM, Wanpeng Li wrote: > >> From: Wanpeng Li > >> > >> The downside of guest side polling is that polling is performed even > >> with other runnable tasks in the host. However, even if poll in kvm > >> can aware whether or not other runnable tasks in the same pCPU, it > >> can still incur extra overhead in over-subscribe scenario. Now we can > >> just enable guest polling when dedicated pCPUs are available. > >> > >> Cc: Rafael J. Wysocki > >> Cc: Paolo Bonzini > >> Cc: Radim Krčmář > >> Cc: Marcelo Tosatti > >> Signed-off-by: Wanpeng Li > > > > Paolo, Marcelo, any comments? > > Yes, it's a good idea. > > Acked-by: Paolo Bonzini > > Paolo I think KVM_HINTS_REALTIME is being abused somewhat. It has no clear meaning and used in different locations for different purposes. For example, i think that using pv queued spinlocks and haltpoll is a desired scenario, which the patch below disallows. Wanpeng Li, currently the driver does not autoload. So polling in the guest has to be enabled manually. Isnt that sufficient?