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=-8.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, 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 35991C2BB1D for ; Thu, 12 Mar 2020 16:36:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0DD2420724 for ; Thu, 12 Mar 2020 16:36:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Hgih+I1u" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726446AbgCLQgM (ORCPT ); Thu, 12 Mar 2020 12:36:12 -0400 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:49230 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726099AbgCLQgL (ORCPT ); Thu, 12 Mar 2020 12:36:11 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1584030970; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=y+zp8ckYFu/JE3Ap00+bCw6jAqD/T1e+8NMqLw5Uqes=; b=Hgih+I1unlcJAEbFwEkIu3/2X0d7meGLWWODaoM1Ih6dlmKB2yMY2QUQrHgZggK3O7aPEZ BxtMwzxoQtzw346ou6bCc3QrxWmcNncEJ8mcU+gAoQvqhonnhJM/3+L1oLzsxF3cHP7HAH sEJAMeaRWXPKOxOCWl/ct3w1TyRHFr8= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-319-UwYhNdmiPAqUzi-XPWcEPg-1; Thu, 12 Mar 2020 12:36:06 -0400 X-MC-Unique: UwYhNdmiPAqUzi-XPWcEPg-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 90D63DBA3; Thu, 12 Mar 2020 16:36:04 +0000 (UTC) Received: from fuller.cnet (ovpn-116-59.gru2.redhat.com [10.97.116.59]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 38D6D19C6A; Thu, 12 Mar 2020 16:36:04 +0000 (UTC) Received: by fuller.cnet (Postfix, from userid 1000) id CEDAF418CC02; Thu, 12 Mar 2020 13:17:51 -0300 (-03) Date: Thu, 12 Mar 2020 13:17:51 -0300 From: Marcelo Tosatti To: "Maciej S. Szmigiero" Cc: "Rafael J. Wysocki" , Daniel Lezcano , Joao Martins , Boris Ostrovsky , kvm@vger.kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] cpuidle-haltpoll: allow force loading on hosts without the REALTIME hint Message-ID: <20200312161751.GA5245@fuller.cnet> References: <20200304113248.1143057-1-mail@maciej.szmigiero.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200304113248.1143057-1-mail@maciej.szmigiero.name> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, Mar 04, 2020 at 12:32:48PM +0100, Maciej S. Szmigiero wrote: > From: "Maciej S. Szmigiero" > > Before commit 1328edca4a14 ("cpuidle-haltpoll: Enable kvm guest polling > when dedicated physical CPUs are available") the cpuidle-haltpoll driver > could also be used in scenarios when the host does not advertise the > KVM_HINTS_REALTIME hint. > > While the behavior introduced by the aforementioned commit makes sense as > the default there are cases where the old behavior is desired, for example, > when other kernel changes triggered by presence by this hint are unwanted, > for some workloads where the latency benefit from polling overweights the > loss from idle CPU capacity that otherwise would be available, or just when > running under older Qemu versions that lack this hint. > > Let's provide a typical "force" module parameter that allows restoring the > old behavior. > > Signed-off-by: Maciej S. Szmigiero > --- > drivers/cpuidle/cpuidle-haltpoll.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > Changes from v1: > Make the module parameter description more general, don't unnecessarily > break a line in haltpoll_init(). > > diff --git a/drivers/cpuidle/cpuidle-haltpoll.c b/drivers/cpuidle/cpuidle-haltpoll.c > index b0ce9bc78113..db124bc1ca2c 100644 > --- a/drivers/cpuidle/cpuidle-haltpoll.c > +++ b/drivers/cpuidle/cpuidle-haltpoll.c > @@ -18,6 +18,10 @@ > #include > #include > > +static bool force __read_mostly; > +module_param(force, bool, 0444); > +MODULE_PARM_DESC(force, "Load unconditionally"); > + > static struct cpuidle_device __percpu *haltpoll_cpuidle_devices; > static enum cpuhp_state haltpoll_hp_state; > > @@ -90,6 +94,11 @@ static void haltpoll_uninit(void) > haltpoll_cpuidle_devices = NULL; > } > > +static bool haltpool_want(void) > +{ > + return kvm_para_has_hint(KVM_HINTS_REALTIME) || force; > +} > + > static int __init haltpoll_init(void) > { > int ret; > @@ -101,8 +110,7 @@ static int __init haltpoll_init(void) > > cpuidle_poll_state_init(drv); > > - if (!kvm_para_available() || > - !kvm_para_has_hint(KVM_HINTS_REALTIME)) > + if (!kvm_para_available() || !haltpool_want()) > return -ENODEV; > > ret = cpuidle_register_driver(drv); Signed-off-by: Marcelo Tosatti