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=-6.3 required=3.0 tests=DATE_IN_PAST_12_24, DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 A41B0C0044D for ; Sun, 15 Mar 2020 03:40:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7C22420578 for ; Sun, 15 Mar 2020 03:40:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584243654; bh=zZ9bAR3baPAPuE8evlBpnNMKiF2jY5NR9uiWv2PkB4c=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=Z9W6lb/3G3MgJrSTyTYXbxOMzKSENqSgeOpmQKq/s3e7nj98peYpi6KPYkiHz+WtB evbcn3oFa699JoxMXsziuBvINzIN0/uiWddu2At6UynHSwSBAhnosBamHG2ahdDiML L5GI3M4IMoK1f0GQfgb8RzJm6JEPFcaij07V2M1Y= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727493AbgCODkv (ORCPT ); Sat, 14 Mar 2020 23:40:51 -0400 Received: from mail-qk1-f193.google.com ([209.85.222.193]:37486 "EHLO mail-qk1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726653AbgCODkv (ORCPT ); Sat, 14 Mar 2020 23:40:51 -0400 Received: by mail-qk1-f193.google.com with SMTP id z25so15299879qkj.4; Sat, 14 Mar 2020 20:40:50 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=xWfNlXspNXP/Z3scX2GkjvDWCTPuiHmONTso2D85LQ0=; b=sGtaPxoOYlnTE5+b5zUoJ5Qn4z0EdmGqcfdkyzpvc+A+oNj2ctggTsHy7R5k5KZaSS bJmMY5PSsrpz4laFSZ4Cvu1/UjYJvYiDHDndj8EmjUyw16JFuCWraRfLM2fLieGE1rw/ t4GXZD+7QD+JKa0naTB5pkynZPCLuLQGIggS7Itm3YqeYqhRene0PWAK7SwTR5eN9yQl +vJlMoXeZ6j0Q6fHxZXu9BH5N9pQBpt0VboKIs4enjv3glrDqAwo24UUnZ50iNeQXMLS LYpw3WcitaT3FUhFNW5aVWy/LP1RCkHJmHHxiXiFyS60KPOk0PPhc36PkRXhY7LOVeLY VzFA== X-Gm-Message-State: ANhLgQ3XMB+dMlygbKdQ6riMKlTY/fWvpG4+Pa5qXNxz0mSZPa0BgrSc UYxcEye81dVp7IqW0xfZETMUf2fnx688Aje0f6bitg== X-Google-Smtp-Source: ADFU+vt9NbYnSnppxGI7xOTmGfRR3RSs/QZOhkMGUVuMhiPSyyT3vdhguRYt/HjQ0hyrQs/pQ8sEHfBxb3po2QAZY0w= X-Received: by 2002:a9d:1d07:: with SMTP id m7mr6029839otm.167.1584182450168; Sat, 14 Mar 2020 03:40:50 -0700 (PDT) MIME-Version: 1.0 References: <20200304113248.1143057-1-mail@maciej.szmigiero.name> <20200312161751.GA5245@fuller.cnet> In-Reply-To: From: "Rafael J. Wysocki" Date: Sat, 14 Mar 2020 11:40:38 +0100 Message-ID: Subject: Re: [PATCH v2] cpuidle-haltpoll: allow force loading on hosts without the REALTIME hint To: "Maciej S. Szmigiero" , Marcelo Tosatti Cc: "Rafael J. Wysocki" , Daniel Lezcano , Joao Martins , Boris Ostrovsky , kvm-devel , Linux PM , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, Mar 13, 2020 at 6:49 PM Rafael J. Wysocki wrote: > > On Thu, Mar 12, 2020 at 5:36 PM Marcelo Tosatti wrote: > > > > 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 > > I'm taking this as a Reviewed-by, thanks! Patch applied as 5.7 material, thanks!