From patchwork Thu Aug 9 17:20:02 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Leo Yan X-Patchwork-Id: 10561605 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id CFA9F13B4 for ; Thu, 9 Aug 2018 17:20:32 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B194A2B76E for ; Thu, 9 Aug 2018 17:20:32 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id A556E2B77D; Thu, 9 Aug 2018 17:20:32 +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=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,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 506AB2B76E for ; Thu, 9 Aug 2018 17:20:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732598AbeHITqJ (ORCPT ); Thu, 9 Aug 2018 15:46:09 -0400 Received: from mail-wr1-f66.google.com ([209.85.221.66]:44558 "EHLO mail-wr1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732368AbeHITqJ (ORCPT ); Thu, 9 Aug 2018 15:46:09 -0400 Received: by mail-wr1-f66.google.com with SMTP id r16-v6so5771558wrt.11 for ; Thu, 09 Aug 2018 10:20:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=tQeOn7z2zgtAWzzjccDSf6WarhVnTGNmsaV0jykRFsI=; b=TK3eGQhsEzCwWSFTTbvyFsnlrIQLoWZkfwZFixu8e2/iKBZxnzwtwpQJzwd4RX5dgt zZ/5m7vCItz9FGqdZUIwDS/bViodUcM+Juf2vbftsbu5Y0GcrVUIHcqY8ktsYBxdrkdh 8zTTDf4K8fDQeNhCqU2W6HAOO+qnTjbMVDz6k= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=tQeOn7z2zgtAWzzjccDSf6WarhVnTGNmsaV0jykRFsI=; b=WW4N3rqWvj/pWXimEhhxQOJnRTWDzWf4vSIBy1jlm+yL9qvsC9HHH4CsyBmDu+dDui PadlLMVBO8afhOwrBplyELWqqenjYPLqTI5neQ1kp6ktHadaWeicX7+ZCla3qGOBRrS7 yP0nVkgol/izi5RTF8y0UsK881BRXvQZRIgGliHhszEIk9RuPcCOCREVLaQK8Wr092/Z FRB9liZmb8LMlYOIAoq5mrMWELfqymphh/CKWB05NdBhLYslOlYQ3pbBUzlVHbBoQbfY weCpR+QpPzV77BAS3jaLCAY4y1rHpvvTaLxtQqhBhw6KdUJlGsOrtaPkdwt8hy7o1MUq uqhw== X-Gm-Message-State: AOUpUlH5b7G0vqIyHMno9p8PcwEUTPzDIkJCdhmMya9g7UnxId/DIb7c Ma+U6rPvYAVfmf2JVAmBcbA6Eg== X-Google-Smtp-Source: AA+uWPy0fXu1xybQYXESqaG3UFZ9uI0uMMXdPqFm1MxVWcVxu0udeWPKDJmrLiF3bXSr2WxynhHjqg== X-Received: by 2002:adf:ed8e:: with SMTP id c14-v6mr1981310wro.264.1533835218448; Thu, 09 Aug 2018 10:20:18 -0700 (PDT) Received: from localhost.localdomain ([45.76.138.171]) by smtp.gmail.com with ESMTPSA id u4-v6sm1815056wro.47.2018.08.09.10.20.15 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Thu, 09 Aug 2018 10:20:17 -0700 (PDT) From: Leo Yan To: "Rafael J. Wysocki" , "Peter Zijlstra (Intel)" , Daniel Lezcano , Vincent Guittot , linux-kernel@vger.kernel.org, Linux PM Cc: Leo Yan Subject: [RESEND PATCH v1 1/2] cpuidle: menu: Correct the criteria for stopping tick Date: Fri, 10 Aug 2018 01:20:02 +0800 Message-Id: <1533835203-5789-2-git-send-email-leo.yan@linaro.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1533835203-5789-1-git-send-email-leo.yan@linaro.org> References: <1533835203-5789-1-git-send-email-leo.yan@linaro.org> 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 The criteria for keeping tick running is the prediction duration is less than TICK_USEC, the mainline kernel configures HZ=250 so TICK_USEC equals to 4000us, so any prediction is less than 4000us will not stop tick and the idle state will be fixed up to one shallow state. On the other hand, let's use 96boards Hikey (CA53 octa-CPUs) as an example, the platform has the deepest C-state is cluster off state which its 'target_residency' is 2700us, if the 'menu' governor predicts the next idle duration is any value fallen into the range [2700us, 4000us), then the 'menu' governor will keep sched tick running and and roll back to a shallow CPU off state rather than cluster off state. Finally we can see the CPU has much less chance to run into deepest state when a task repeatedly running on it with 5000us period and 40% duty cycle (so the task runs for 2000us and then sleep for 3000us in every period). In theory, we should permit the CPU to stay in cluster off state due the CPU sleeping time 3000us is over its 'target_residency' 2700us. This issue is caused by the 'menu' governor's criteria for decision if need to enable tick and roll back to shallow state, the criteria is: 'expected_interval < TICK_USEC'. This criteria is only considering from tick aspect, but it doesn't consider idle state residency so misses better choice for deeper idle state; e.g., the deepest idle state 'target_residency' is less than TICK_USEC, which is quite common on Arm platforms. To fix this issue, this patch is to add one extra variable 'stop_tick_point' to help decision if need to stop tick or not. If prediction is longer than 'stop_tick_point' then we can stop tick, otherwise it will keep tick running. For 'stop_tick_point', except we need to compare prediction period with TICK_USEC, we also need consider from the perspective of deepest idle state 'target_residency'. Finally, 'stop_tick_point' is coming from the minimum value within the deepest idle state 'target_residency' and TICK_USEC. Cc: Daniel Lezcano Cc: Vincent Guittot Signed-off-by: Leo Yan --- drivers/cpuidle/governors/menu.c | 41 ++++++++++++++++++++++++++++++++++++++-- 1 file changed, 39 insertions(+), 2 deletions(-) diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c index 30ab759..2ce4068 100644 --- a/drivers/cpuidle/governors/menu.c +++ b/drivers/cpuidle/governors/menu.c @@ -294,6 +294,7 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, unsigned int expected_interval; unsigned long nr_iowaiters, cpu_load; ktime_t delta_next; + unsigned int stop_tick_point; if (data->needs_update) { menu_update(drv, dev); @@ -406,11 +407,47 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, idx = 0; /* No states enabled. Must use 0. */ /* + * Decide the time point for tick stopping, if the prediction is before + * this time point it's better to keep the tick enabled and after the + * time point it means the CPU can stay in idle state for enough long + * time so should stop the tick. This point needs to consider two + * factors: the first one is tick period and the another factor is the + * maximum target residency. + * + * We can divide into below cases: + * + * The first case is the prediction is shorter than the maximum target + * residency and also shorter than tick period, this means the + * prediction isn't to use deepest idle state and it's suppose the CPU + * will be waken up within tick period, for this case we should keep + * the tick to be enabled; + * + * The second case is the prediction is shorter than the maximum target + * residency and longer than tick period, for this case the idle state + * selection has already based on the prediction for shallow state and + * we will expect some events can arrive later than tick to wake up the + * CPU; another thinking for this case is the CPU is likely to stay in + * the expected idle state for long while (which should be longer than + * tick period), so it's reasonable to stop the tick. + * + * The third case is the prediction is longer than the maximum target + * residency, but weather it's longer or shorter than tick period; for + * this case we have selected the deepest idle state so it's pointless + * to enable tick to wake up CPU from deepest state. + * + * To summary upper cases, we use the value of min(TICK_USEC, + * maximum_target_residency) as the critical point to decide if need to + * stop tick. + */ + stop_tick_point = min_t(unsigned int, TICK_USEC, + drv->states[drv->state_count-1].target_residency); + + /* * Don't stop the tick if the selected state is a polling one or if the - * expected idle duration is shorter than the tick period length. + * expected idle duration is shorter than the estimated stop tick point. */ if ((drv->states[idx].flags & CPUIDLE_FLAG_POLLING) || - expected_interval < TICK_USEC) { + expected_interval < stop_tick_point) { unsigned int delta_next_us = ktime_to_us(delta_next); *stop_tick = false; From patchwork Thu Aug 9 17:20:03 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Leo Yan X-Patchwork-Id: 10561603 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 4DC26139A for ; 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Thu, 9 Aug 2018 15:46:13 -0400 Received: by mail-wr1-f68.google.com with SMTP id r16-v6so5771722wrt.11 for ; Thu, 09 Aug 2018 10:20:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=GF32Bje0oJAW4XeP8mIAbg+OAE7k9UA39pRZeiSkJP4=; b=FZ+dmIhZlQcz0kpao5gO2k+08QBuZGit29vjGX6HxlGHF6NDVaw9xNgIPFqqnOBnJy Q+nCBblp4OhI7XsVKbeBxeqTeSwYAhFZ1G/xgyvs3By5sluJRot66KCwebPACisx1zEZ Nke8PFj/26ee5U2I+KFbkToWebSMH8AGKSLOY= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=GF32Bje0oJAW4XeP8mIAbg+OAE7k9UA39pRZeiSkJP4=; b=E5M2rGFWTXroiW92H2iAeKzApfkJa1nAqE22HtJKKNkV3ZIrz7j0SfxcOY1VXrbSXi gI4wV+2SQyBvoPXpugjNUKfcJbfaBCN+AX5cAzO0CckyqSeo/usNemx8l7lnADsdTjG2 fJfQtDM4fxUUBdzcwZRKDIUfjK0TcTIxl+0VrLPrlpBwC/7qT7aWI/vkMjiFVW0edcQD Kg9zW5AnOIKqe42ok+PJ5AcibXu5e59U4+plIZ2iC/aqLzJ6ZZpykmcJZKpuPTnL1MOH wvdIFsB7mCAuAWanvv/+UrfgJ4J+iWP9E2VgZNNGo9CnAOC1nTj81kB5RJa7MB/2WZmF f5yw== X-Gm-Message-State: AOUpUlFsryMAF4eOMiTvV4lhP6va65dX0BQcfPmIrW2yCgmh1PB01Mjc iWmvgoiDS7d9Vo1aKAPTDLNnRQ== X-Google-Smtp-Source: AA+uWPwWSoeOw1sBh6X3LnbVMnjY3iVilUBHcpx07fmcOHHUST0lNpt6bMejqwvFyGdPLnrfC5LjyA== X-Received: by 2002:adf:fdcd:: with SMTP id i13-v6mr1945680wrs.276.1533835222153; Thu, 09 Aug 2018 10:20:22 -0700 (PDT) Received: from localhost.localdomain ([45.76.138.171]) by smtp.gmail.com with ESMTPSA id u4-v6sm1815056wro.47.2018.08.09.10.20.18 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Thu, 09 Aug 2018 10:20:21 -0700 (PDT) From: Leo Yan To: "Rafael J. Wysocki" , "Peter Zijlstra (Intel)" , Daniel Lezcano , Vincent Guittot , linux-kernel@vger.kernel.org, Linux PM Cc: Leo Yan Subject: [RESEND PATCH v1 2/2] cpuidle: menu: Dismiss tick impaction on correction factors Date: Fri, 10 Aug 2018 01:20:03 +0800 Message-Id: <1533835203-5789-3-git-send-email-leo.yan@linaro.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1533835203-5789-1-git-send-email-leo.yan@linaro.org> References: <1533835203-5789-1-git-send-email-leo.yan@linaro.org> 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 If the idle duration predictor detects the tick is triggered, and with meeting the condition 'data->next_timer_us > TICK_USEC', it will give a big compensation for the 'measured' interval; this is purposed to avoid artificially small correction factor values. Unfortunately, this still cannot cover all cases of the tick impaction on correction factors, e.g. if the predicted next event is less than ITCK_USEC, then all wakening up by the ticks will be taken as usual case and reducing exit latency, as results the tick events heavily impacts the correction factors. Moreover, the coming tick sometimes is very soon, especially at the first time when the CPU becomes idle the tick expire time might be vary, so ticks can introduce big deviation on correction factors. If idle governor deliberately doesn't stop the tick timer, the tick event is coming as expected with fixed interval, so the tick event is predictable; if the tick event is coming early than other normal timer event and other possible wakeup events, we need to dismiss the tick impaction on correction factors, this can let the correction factor array is purely used for other wakeup events correctness rather than sched tick. This patch is to check if it's a tick wakeup, it takes the CPU can stay in the idle state for enough time so it gives high compensation for the measured' interval, this can avoid tick impaction on the correction factor array. Cc: Daniel Lezcano Cc: Vincent Guittot Signed-off-by: Leo Yan --- drivers/cpuidle/governors/menu.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c index 2ce4068..43cbde3 100644 --- a/drivers/cpuidle/governors/menu.c +++ b/drivers/cpuidle/governors/menu.c @@ -525,15 +525,13 @@ static void menu_update(struct cpuidle_driver *drv, struct cpuidle_device *dev) * assume the state was never reached and the exit latency is 0. */ - if (data->tick_wakeup && data->next_timer_us > TICK_USEC) { + if (data->tick_wakeup) { /* - * The nohz code said that there wouldn't be any events within - * the tick boundary (if the tick was stopped), but the idle - * duration predictor had a differing opinion. Since the CPU - * was woken up by a tick (that wasn't stopped after all), the - * predictor was not quite right, so assume that the CPU could - * have been idle long (but not forever) to help the idle - * duration predictor do a better job next time. + * Since the CPU was woken up by a tick (that wasn't stopped + * after all), the predictor was not quite right, so assume + * that the CPU could have been idle long (but not forever) + * to help the idle duration predictor do a better job next + * time. */ measured_us = 9 * MAX_INTERESTING / 10; } else {