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=-17.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham 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 365EBC433ED for ; Wed, 7 Apr 2021 15:29:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0F0DF61284 for ; Wed, 7 Apr 2021 15:29:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353594AbhDGP3a (ORCPT ); Wed, 7 Apr 2021 11:29:30 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:37909 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353528AbhDGP32 (ORCPT ); Wed, 7 Apr 2021 11:29:28 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1617809357; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type; bh=lt6zYqYQXzJ6nG3sWMwPo3r3/e2UA4fAW7Oz3w0+DpU=; b=UBCJhiUFjQ8L5aX2X6+kUFKD7VzwNEPESXVmxc3fJV1/Jg6njwuqv7clERhVoBO9yzZTdK veor16ihPXn0/w3eUKK7YAqGzWpx5GNz3H7WkR7VI4b2GV324HrhVQzxn6QvBcQhfhSTXI IU2+gfMBkZvwtY4JRV/Uf2yUWfEQGKk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-417-lxbv5R-vO1y3hTr9E94DXQ-1; Wed, 07 Apr 2021 11:28:26 -0400 X-MC-Unique: lxbv5R-vO1y3hTr9E94DXQ-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 87523A0CAC; Wed, 7 Apr 2021 15:28:22 +0000 (UTC) Received: from fuller.cnet (ovpn-112-5.gru2.redhat.com [10.97.112.5]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E9F5D2BFE7; Wed, 7 Apr 2021 15:28:14 +0000 (UTC) Received: by fuller.cnet (Postfix, from userid 1000) id 559BC41486DD; Wed, 7 Apr 2021 10:53:01 -0300 (-03) Date: Wed, 7 Apr 2021 10:53:01 -0300 From: Marcelo Tosatti To: Thomas Gleixner Cc: linux-kernel@vger.kernel.org, Frederic Weisbecker , Peter Xu , Nitesh Narayan Lal , Alex Belits Subject: [PATCH] hrtimer: avoid retrigger_next_event IPI Message-ID: <20210407135301.GA16985@fuller.cnet> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Setting the realtime clock triggers an IPI to all CPUs to reprogram hrtimers. However, only base, boottime and tai clocks have their offsets updated (and therefore potentially require a reprogram). If the CPU is a nohz_full one, check if it only has monotonic active timers, and in that case update the realtime base offsets, skipping the IPI. This reduces interruptions to nohz_full CPUs. Signed-off-by: Marcelo Tosatti diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index 743c852e10f2..b42b1a434b22 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -853,6 +853,28 @@ static void hrtimer_reprogram(struct hrtimer *timer, bool reprogram) tick_program_event(expires, 1); } +#define CLOCK_SET_BASES ((1U << HRTIMER_BASE_REALTIME)| \ + (1U << HRTIMER_BASE_REALTIME_SOFT)| \ + (1U << HRTIMER_BASE_BOOTTIME)| \ + (1U << HRTIMER_BASE_BOOTTIME_SOFT)| \ + (1U << HRTIMER_BASE_TAI)| \ + (1U << HRTIMER_BASE_TAI_SOFT)) + +static bool need_reprogram_timer(struct hrtimer_cpu_base *cpu_base) +{ + unsigned int active = 0; + + if (!cpu_base->softirq_activated) + active = cpu_base->active_bases & HRTIMER_ACTIVE_SOFT; + + active = active | (cpu_base->active_bases & HRTIMER_ACTIVE_HARD); + + if ((active & CLOCK_SET_BASES) == 0) + return false; + + return true; +} + /* * Clock realtime was set * @@ -867,9 +889,41 @@ static void hrtimer_reprogram(struct hrtimer *timer, bool reprogram) void clock_was_set(void) { #ifdef CONFIG_HIGH_RES_TIMERS - /* Retrigger the CPU local events everywhere */ - on_each_cpu(retrigger_next_event, NULL, 1); + cpumask_var_t mask; + int cpu; + + if (!tick_nohz_full_enabled()) { + /* Retrigger the CPU local events everywhere */ + on_each_cpu(retrigger_next_event, NULL, 1); + goto set_timerfd; + } + + if (!zalloc_cpumask_var(&mask, GFP_KERNEL)) { + on_each_cpu(retrigger_next_event, NULL, 1); + goto set_timerfd; + } + + /* Avoid interrupting nohz_full CPUs if possible */ + preempt_disable(); + for_each_online_cpu(cpu) { + if (tick_nohz_full_cpu(cpu)) { + unsigned long flags; + struct hrtimer_cpu_base *cpu_base = &per_cpu(hrtimer_bases, cpu); + + raw_spin_lock_irqsave(&cpu_base->lock, flags); + if (need_reprogram_timer(cpu_base)) + cpumask_set_cpu(cpu, mask); + else + hrtimer_update_base(cpu_base); + raw_spin_unlock_irqrestore(&cpu_base->lock, flags); + } + } + + smp_call_function_many(mask, retrigger_next_event, NULL, 1); + preempt_enable(); + free_cpumask_var(mask); #endif +set_timerfd: timerfd_clock_was_set(); }