From patchwork Mon Mar 12 09:36:27 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Rafael J. Wysocki" X-Patchwork-Id: 10275759 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 9DF6B6038F for ; Mon, 12 Mar 2018 09:35:52 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9D55A28CAC for ; Mon, 12 Mar 2018 09:35:52 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 8FE1728CCA; Mon, 12 Mar 2018 09:35:52 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2005128CAC for ; Mon, 12 Mar 2018 09:35:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751401AbeCLJfu (ORCPT ); Mon, 12 Mar 2018 05:35:50 -0400 Received: from cloudserver094114.home.pl ([79.96.170.134]:65069 "EHLO cloudserver094114.home.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751229AbeCLJfu (ORCPT ); Mon, 12 Mar 2018 05:35:50 -0400 Received: from 79.184.254.228.ipv4.supernova.orange.pl (79.184.254.228) (HELO aspire.rjw.lan) by serwer1319399.home.pl (79.96.170.134) with SMTP (IdeaSmtpServer 0.83) id d6661e6b052863c0; Mon, 12 Mar 2018 10:35:48 +0100 From: "Rafael J. Wysocki" To: Linux PM Cc: Peter Zijlstra , Frederic Weisbecker , Thomas Gleixner , Paul McKenney , Thomas Ilsche , Doug Smythies , Rik van Riel , Aubrey Li , Mike Galbraith , LKML Subject: [PATCH v2] cpuidle: poll_state: Add time limit to poll_idle() Date: Mon, 12 Mar 2018 10:36:27 +0100 Message-ID: <4137867.C4jYrWdt8n@aspire.rjw.lan> MIME-Version: 1.0 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Rafael J. Wysocki If poll_idle() is allowed to spin until need_resched() returns 'true', it may actually spin for a much longer time than expected by the idle governor, since set_tsk_need_resched() is not always called by the timer interrupt handler. If that happens, the CPU may spend much more time than anticipated in the "polling" state. To prevent that from happening, limit the time of the spinning loop in poll_idle(). Signed-off-by: Rafael J. Wysocki --- -> v2: After additional testing reduce POLL_IDLE_TIME_CHECK_COUNT to 1000. --- drivers/cpuidle/poll_state.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) Index: linux-pm/drivers/cpuidle/poll_state.c =================================================================== --- linux-pm.orig/drivers/cpuidle/poll_state.c +++ linux-pm/drivers/cpuidle/poll_state.c @@ -5,16 +5,31 @@ */ #include +#include #include #include +#define POLL_IDLE_TIME_CHECK_COUNT 1000 +#define POLL_IDLE_TIME_LIMIT (TICK_NSEC / 16) + static int __cpuidle poll_idle(struct cpuidle_device *dev, struct cpuidle_driver *drv, int index) { + ktime_t start = ktime_get(); + local_irq_enable(); if (!current_set_polling_and_test()) { - while (!need_resched()) + unsigned int time_check_counter = 0; + + while (!need_resched()) { cpu_relax(); + if (time_check_counter++ < POLL_IDLE_TIME_CHECK_COUNT) + continue; + + time_check_counter = 0; + if (ktime_sub(ktime_get(), start) > POLL_IDLE_TIME_LIMIT) + break; + } } current_clr_polling();