From patchwork Fri Feb 21 17:43:31 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Maciej S. Szmigiero" X-Patchwork-Id: 11397101 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 83D1B14BC for ; Fri, 21 Feb 2020 18:12:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6CA9D24676 for ; Fri, 21 Feb 2020 18:12:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725995AbgBUSM2 (ORCPT ); Fri, 21 Feb 2020 13:12:28 -0500 Received: from vps-vb.mhejs.net ([37.28.154.113]:50782 "EHLO vps-vb.mhejs.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725947AbgBUSM2 (ORCPT ); Fri, 21 Feb 2020 13:12:28 -0500 X-Greylist: delayed 1727 seconds by postgrey-1.27 at vger.kernel.org; Fri, 21 Feb 2020 13:12:27 EST Received: from MUA by vps-vb.mhejs.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.92.3) (envelope-from ) id 1j5CKv-0002wU-0a; Fri, 21 Feb 2020 18:43:37 +0100 From: "Maciej S. Szmigiero" To: "Rafael J. Wysocki" , Daniel Lezcano Cc: Joao Martins , Boris Ostrovsky , linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] cpuidle-haltpoll: allow force loading on hosts without the REALTIME hint Date: Fri, 21 Feb 2020 18:43:31 +0100 Message-Id: <20200221174331.1480468-1-mail@maciej.szmigiero.name> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org 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, 11 insertions(+), 1 deletion(-) diff --git a/drivers/cpuidle/cpuidle-haltpoll.c b/drivers/cpuidle/cpuidle-haltpoll.c index b0ce9bc78113..07e5b36076bb 100644 --- a/drivers/cpuidle/cpuidle-haltpoll.c +++ b/drivers/cpuidle/cpuidle-haltpoll.c @@ -18,6 +18,11 @@ #include #include +static bool force __read_mostly; +module_param(force, bool, 0444); +MODULE_PARM_DESC(force, + "Load even if the host does not provide the REALTIME hint"); + static struct cpuidle_device __percpu *haltpoll_cpuidle_devices; static enum cpuhp_state haltpoll_hp_state; @@ -90,6 +95,11 @@ 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; @@ -102,7 +112,7 @@ static int __init haltpoll_init(void) cpuidle_poll_state_init(drv); if (!kvm_para_available() || - !kvm_para_has_hint(KVM_HINTS_REALTIME)) + !haltpool_want()) return -ENODEV; ret = cpuidle_register_driver(drv);