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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 93067C10F14 for ; Thu, 10 Oct 2019 21:37:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6B6BB20B7C for ; Thu, 10 Oct 2019 21:37:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727301AbfJJVhm (ORCPT ); Thu, 10 Oct 2019 17:37:42 -0400 Received: from cloudserver094114.home.pl ([79.96.170.134]:58988 "EHLO cloudserver094114.home.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725867AbfJJVhl (ORCPT ); Thu, 10 Oct 2019 17:37:41 -0400 Received: from 79.184.255.36.ipv4.supernova.orange.pl (79.184.255.36) (HELO kreacher.localnet) by serwer1319399.home.pl (79.96.170.134) with SMTP (IdeaSmtpServer 0.83.292) id cd4238d3936759af; Thu, 10 Oct 2019 23:37:39 +0200 From: "Rafael J. Wysocki" To: "Rafael J. Wysocki" Cc: Linux PM , LKML , Srinivas Pandruvada , Peter Zijlstra , Daniel Lezcano , Doug Smythies Subject: [PATCH 4/4] cpuidle: teo: Fix "early hits" handling for disabled idle states Date: Thu, 10 Oct 2019 23:37:39 +0200 Message-ID: <1746940.X44tFrgt99@kreacher> In-Reply-To: <60416800.X4hXmAfbqi@kreacher> References: <60416800.X4hXmAfbqi@kreacher> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Rafael J. Wysocki The TEO governor uses idle duration "bins" defined in accordance with the CPU idle states table provided by the driver, so that each "bin" covers the idle duration range between the target residency of the idle state corresponding to it and the target residency of the closest deeper idle state. The governor collects statistics for each bin regardless of whether or not the idle state corresponding to it is currently enabled. In particular, the "early hits" metric measures the likelihood of a situation in which the idle duration measured after wakeup falls into to given bin, but the time till the next timer (sleep length) falls into a bin corresponding to one of the deeper idle states. It is used when the "hits" and "misses" metrics indicate that the state "matching" the sleep length should not be selected, so that the state with the maximum "early hits" value is selected instead of it. If the idle state corresponding to the given bin is disabled, it cannot be selected and if it turns out to be the one that should be selected, a shallower idle state needs to be used instead of it. Nevertheless, the metrics collected for the bin corresponding to it are still valid and need to be taken into account as though that state had not been disabled. As far as the "early hits" metric is concerned, teo_select() tries to take disabled states into account, but the state index corresponding to the maximum "early hits" value computed by it may be incorrect. Namely, it always uses the index of the previous maximum "early hits" state then, but there may be enabled idle states closer to the disabled one in question. In particular, if the current candidate state (whose index is the idx value) is closer to the disabled one and the "early hits" value of the disabled state is greater than the current maximum, the index of the current candidate state (idx) should replace the "maximum early hits state" index. Modify the code to handle that case correctly. Fixes: b26bf6ab716f ("cpuidle: New timer events oriented governor for tickless systems") Reported-by: Doug Smythies Signed-off-by: Rafael J. Wysocki --- drivers/cpuidle/governors/teo.c | 35 ++++++++++++++++++++++++++--------- 1 file changed, 26 insertions(+), 9 deletions(-) Index: linux-pm/drivers/cpuidle/governors/teo.c =================================================================== --- linux-pm.orig/drivers/cpuidle/governors/teo.c +++ linux-pm/drivers/cpuidle/governors/teo.c @@ -277,18 +277,35 @@ static int teo_select(struct cpuidle_dri hits = cpu_data->states[i].hits; misses = cpu_data->states[i].misses; + if (early_hits >= cpu_data->states[i].early_hits || + idx < 0) + continue; + + /* + * If the current candidate state has been the one with + * the maximum "early hits" metric so far, the "early + * hits" metric of the disabled state replaces the + * current "early hits" count to avoid selecting a + * deeper state with lower "early hits" metric. + */ + if (max_early_idx == idx) { + early_hits = cpu_data->states[i].early_hits; + continue; + } + /* - * If the "early hits" metric of a disabled state is - * greater than the current maximum, it should be taken - * into account, because it would be a mistake to select - * a deeper state with lower "early hits" metric. The - * index cannot be changed to point to it, however, so - * just increase the "early hits" count alone and let - * the index still point to a shallower idle state. + * The current candidate state is closer to the disabled + * one than the current maximum "early hits" state, so + * replace the latter with it, but in case the maximum + * "early hits" state index has not been set so far, + * check if the current candidate state is not too + * shallow for that role. */ - if (max_early_idx >= 0 && - early_hits < cpu_data->states[i].early_hits) + if (!(tick_nohz_tick_stopped() && + drv->states[idx].target_residency < TICK_USEC)) { early_hits = cpu_data->states[i].early_hits; + max_early_idx = idx; + } continue; }