From patchwork Wed Sep 16 06:45:28 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Viresh Kumar X-Patchwork-Id: 11779129 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 3BB4E59D for ; Wed, 16 Sep 2020 06:45:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 18F8520770 for ; Wed, 16 Sep 2020 06:45:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="n+szBhQ/" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726210AbgIPGps (ORCPT ); Wed, 16 Sep 2020 02:45:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44988 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726189AbgIPGpr (ORCPT ); Wed, 16 Sep 2020 02:45:47 -0400 Received: from mail-pj1-x1041.google.com (mail-pj1-x1041.google.com [IPv6:2607:f8b0:4864:20::1041]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F0E77C061788 for ; Tue, 15 Sep 2020 23:45:46 -0700 (PDT) Received: by mail-pj1-x1041.google.com with SMTP id mm21so1056811pjb.4 for ; Tue, 15 Sep 2020 23:45:46 -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 :mime-version:content-transfer-encoding; bh=eVoj/Y7hhEmWcOFF7SkEdYZfa2skHwatr+eS0o7Q9yk=; b=n+szBhQ/7hLOh3i8vQAg7nmEUOn/cXc5TXnyfxzZEitj/nyEyJyEP2jCyGxE9Sv5T9 e2VmbDKzMs3liv8Pzc4XkUsF0OeCJVb3Y/5B8R0dziN8MQYeXPpqhVg4M7EfcOSwWoKV qcWblFbTv/eHecb9sRu5TILzCukoXdEgQEGRNWprxAbSNY66jt3zVPb9klsM1kf7zyJq t40SyHfHQUrHpCk1XWtdyhlqmgUNYDtvLWs4eMPV+q1PQtHSG8VhwcEk6XFIYLynN/U9 06tOy+rbumit3iRseFtPFjE/xE5jwLK4fYnchCliiPJ0eXDibtSt/bUMLXl8uj7SXYLG GLNw== 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:mime-version:content-transfer-encoding; bh=eVoj/Y7hhEmWcOFF7SkEdYZfa2skHwatr+eS0o7Q9yk=; b=TFHhzB6GgAePgbPN3SUW+nLiqBe8j+0dXUE5rp1Ln4JvV0wxXdBDyQDTQ+TbjqIshT xgJODhZt4ZCtEvpds/I1k8gdgZiyIOZZyLWq4uFO3B+mPhj2aA5uE8e9CuHmepvOIZwR 7rJtcxpsc6lYMtzssjkwLMrrH6eB5Jhc3USDXSXAUKcZB2A7hLJdlziwGRkYJ+TD+CLm Wu6I1CdDW6E3lYQXBWqOZCDhehelbN+1z9LNSrr5EuAXtWqnN8lahgYil2y7ZMypl/IN 6NarUihql6Litymf6J8rJOx8w6AW5FhUSG+N3GIsbKaAR9DGDLNJ4vuGNy2pK1GdG117 ZVJg== X-Gm-Message-State: AOAM532wip+hNFM+c1jUj7KO82Jmg46YNUoDXeMUHxnv2shoH9d/m2h+ OsjQg40eVrCxrvYyu0YjeAwE8Q== X-Google-Smtp-Source: ABdhPJwYSxPJhKE9AWiA5IBejWBYN+GiAYyaL9vZu/cmrDJZ8jZfy5LbHajV2rLB7DeIWFauGzxbhg== X-Received: by 2002:a17:90a:f117:: with SMTP id cc23mr2627310pjb.155.1600238746495; Tue, 15 Sep 2020 23:45:46 -0700 (PDT) Received: from localhost ([122.181.54.133]) by smtp.gmail.com with ESMTPSA id a27sm15586944pfk.52.2020.09.15.23.45.45 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 15 Sep 2020 23:45:45 -0700 (PDT) From: Viresh Kumar To: Rafael Wysocki , Viresh Kumar Cc: linux-pm@vger.kernel.org, Vincent Guittot , Lukasz Luba , cristian.marussi@arm.com, sudeep.holla@arm.com, linux-kernel@vger.kernel.org Subject: [PATCH V2 1/4] cpufreq: stats: Defer stats update to cpufreq_stats_record_transition() Date: Wed, 16 Sep 2020 12:15:28 +0530 Message-Id: <31999d801bfb4d8063dc1ceec1234b6b80b4ae68.1600238586.git.viresh.kumar@linaro.org> X-Mailer: git-send-email 2.25.0.rc1.19.g042ed3e048af In-Reply-To: References: MIME-Version: 1.0 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org In order to prepare for lock-less stats update, add support to defer any updates to it until cpufreq_stats_record_transition() is called. Signed-off-by: Viresh Kumar --- drivers/cpufreq/cpufreq_stats.c | 75 ++++++++++++++++++++++++--------- 1 file changed, 56 insertions(+), 19 deletions(-) diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c index 94d959a8e954..3e7eee29ee86 100644 --- a/drivers/cpufreq/cpufreq_stats.c +++ b/drivers/cpufreq/cpufreq_stats.c @@ -22,17 +22,22 @@ struct cpufreq_stats { spinlock_t lock; unsigned int *freq_table; unsigned int *trans_table; + + /* Deferred reset */ + unsigned int reset_pending; + unsigned long long reset_time; }; -static void cpufreq_stats_update(struct cpufreq_stats *stats) +static void cpufreq_stats_update(struct cpufreq_stats *stats, + unsigned long long time) { unsigned long long cur_time = get_jiffies_64(); - stats->time_in_state[stats->last_index] += cur_time - stats->last_time; + stats->time_in_state[stats->last_index] += cur_time - time; stats->last_time = cur_time; } -static void cpufreq_stats_clear_table(struct cpufreq_stats *stats) +static void cpufreq_stats_reset_table(struct cpufreq_stats *stats) { unsigned int count = stats->max_state; @@ -41,42 +46,67 @@ static void cpufreq_stats_clear_table(struct cpufreq_stats *stats) memset(stats->trans_table, 0, count * count * sizeof(int)); stats->last_time = get_jiffies_64(); stats->total_trans = 0; + + /* Adjust for the time elapsed since reset was requested */ + WRITE_ONCE(stats->reset_pending, 0); + cpufreq_stats_update(stats, stats->reset_time); spin_unlock(&stats->lock); } static ssize_t show_total_trans(struct cpufreq_policy *policy, char *buf) { - return sprintf(buf, "%d\n", policy->stats->total_trans); + struct cpufreq_stats *stats = policy->stats; + + if (READ_ONCE(stats->reset_pending)) + return sprintf(buf, "%d\n", 0); + else + return sprintf(buf, "%d\n", stats->total_trans); } cpufreq_freq_attr_ro(total_trans); static ssize_t show_time_in_state(struct cpufreq_policy *policy, char *buf) { struct cpufreq_stats *stats = policy->stats; + bool pending = READ_ONCE(stats->reset_pending); + unsigned long long time; ssize_t len = 0; int i; if (policy->fast_switch_enabled) return 0; - spin_lock(&stats->lock); - cpufreq_stats_update(stats); - spin_unlock(&stats->lock); - for (i = 0; i < stats->state_num; i++) { + if (pending) { + if (i == stats->last_index) + time = get_jiffies_64() - stats->reset_time; + else + time = 0; + } else { + time = stats->time_in_state[i]; + if (i == stats->last_index) + time += get_jiffies_64() - stats->last_time; + } + len += sprintf(buf + len, "%u %llu\n", stats->freq_table[i], - (unsigned long long) - jiffies_64_to_clock_t(stats->time_in_state[i])); + jiffies_64_to_clock_t(time)); } return len; } cpufreq_freq_attr_ro(time_in_state); +/* We don't care what is written to the attribute */ static ssize_t store_reset(struct cpufreq_policy *policy, const char *buf, size_t count) { - /* We don't care what is written to the attribute. */ - cpufreq_stats_clear_table(policy->stats); + struct cpufreq_stats *stats = policy->stats; + + /* + * Defer resetting of stats to cpufreq_stats_record_transition() to + * avoid races. + */ + WRITE_ONCE(stats->reset_pending, 1); + stats->reset_time = get_jiffies_64(); + return count; } cpufreq_freq_attr_wo(reset); @@ -84,8 +114,9 @@ cpufreq_freq_attr_wo(reset); static ssize_t show_trans_table(struct cpufreq_policy *policy, char *buf) { struct cpufreq_stats *stats = policy->stats; + bool pending = READ_ONCE(stats->reset_pending); ssize_t len = 0; - int i, j; + int i, j, count; if (policy->fast_switch_enabled) return 0; @@ -113,8 +144,13 @@ static ssize_t show_trans_table(struct cpufreq_policy *policy, char *buf) for (j = 0; j < stats->state_num; j++) { if (len >= PAGE_SIZE) break; - len += scnprintf(buf + len, PAGE_SIZE - len, "%9u ", - stats->trans_table[i*stats->max_state+j]); + + if (pending) + count = 0; + else + count = stats->trans_table[i * stats->max_state + j]; + + len += scnprintf(buf + len, PAGE_SIZE - len, "%9u ", count); } if (len >= PAGE_SIZE) break; @@ -228,10 +264,11 @@ void cpufreq_stats_record_transition(struct cpufreq_policy *policy, struct cpufreq_stats *stats = policy->stats; int old_index, new_index; - if (!stats) { - pr_debug("%s: No stats found\n", __func__); + if (!stats) return; - } + + if (READ_ONCE(stats->reset_pending)) + cpufreq_stats_reset_table(stats); old_index = stats->last_index; new_index = freq_table_get_index(stats, new_freq); @@ -241,7 +278,7 @@ void cpufreq_stats_record_transition(struct cpufreq_policy *policy, return; spin_lock(&stats->lock); - cpufreq_stats_update(stats); + cpufreq_stats_update(stats, stats->last_time); stats->last_index = new_index; stats->trans_table[old_index * stats->max_state + new_index]++;