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 CB894C433ED for ; Thu, 15 Apr 2021 20:40:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9955B613A9 for ; Thu, 15 Apr 2021 20:40:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235367AbhDOUlP (ORCPT ); Thu, 15 Apr 2021 16:41:15 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:44296 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234536AbhDOUlO (ORCPT ); Thu, 15 Apr 2021 16:41:14 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618519250; 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: in-reply-to:in-reply-to:references:references; bh=CsPfzp1p/2pzO6cfMOH8ycpbd/j0e31h/uzGn/wi2UA=; b=CXl4G4eIuCuDDD56alL3iD76JXs4+uUmIGDa11wBaEGHapEBLrhkqJDPsUlfjYPUJniWIZ bDLmWcXhU3k/VM8G5oAesKqfthayQHpR8lU0Z/D/MckvvSREar8r9dBF43bsE0PZ7pIkO1 pQyhostxcXR1Ahh/nBpK/9tziCLgTYU= 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-318-xxC1izwgM6SfYI9q4iVU8A-1; Thu, 15 Apr 2021 16:40:46 -0400 X-MC-Unique: xxC1izwgM6SfYI9q4iVU8A-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 57581874998; Thu, 15 Apr 2021 20:40:45 +0000 (UTC) Received: from fuller.cnet (ovpn-112-4.gru2.redhat.com [10.97.112.4]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9B5AC10074E1; Thu, 15 Apr 2021 20:40:38 +0000 (UTC) Received: by fuller.cnet (Postfix, from userid 1000) id 22E994179B89; Thu, 15 Apr 2021 17:40:17 -0300 (-03) Date: Thu, 15 Apr 2021 17:40:17 -0300 From: Marcelo Tosatti To: Thomas Gleixner Cc: Anna-Maria Behnsen , linux-kernel@vger.kernel.org, Frederic Weisbecker , Peter Xu , Nitesh Narayan Lal , Alex Belits Subject: [PATCH v4] hrtimer: avoid retrigger_next_event IPI Message-ID: <20210415204017.GA111847@fuller.cnet> References: <20210407135301.GA16985@fuller.cnet> <87o8en4k9a.ffs@nanos.tec.linutronix.de> <20210409165146.GA40118@fuller.cnet> <87lf9q4lue.ffs@nanos.tec.linutronix.de> <20210413170431.GA16190@fuller.cnet> <20210415153935.GA69750@fuller.cnet> <87im4nv0fh.ffs@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87im4nv0fh.ffs@nanos.tec.linutronix.de> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Setting the realtime clock triggers an IPI to all CPUs to reprogram the clock event device. However, only realtime and TAI clocks have their offsets updated (and therefore potentially require a reprogram). Instead of sending an IPI unconditionally, check each per CPU hrtimer base whether it has active timers in the CLOCK_REALTIME and CLOCK_TAI bases. If that's not the case, update the realtime and TAI base offsets remotely and skip the IPI. This ensures that any subsequently armed timers on CLOCK_REALTIME and CLOCK_TAI are evaluated with the correct offsets. Signed-off-by: Marcelo Tosatti --- v4: - Drop unused code (Thomas). v3: - Nicer changelog (Thomas). - Code style fixes (Thomas). - Compilation warning with CONFIG_HIGH_RES_TIMERS=n (Thomas). - Shrink preemption disabled section (Thomas). v2: - Only REALTIME and TAI bases are affected by offset-to-monotonic changes (Thomas). - Don't special case nohz_full CPUs (Thomas). diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index 5c9d968187ae..e228c0a0c98f 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -871,6 +871,19 @@ 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_TAI) | \ + (1U << HRTIMER_BASE_TAI_SOFT)) + +static bool need_reprogram_timer(struct hrtimer_cpu_base *cpu_base) +{ + if (cpu_base->softirq_activated) + return true; + + return (cpu_base->active_bases & CLOCK_SET_BASES) != 0; +} + /* * Clock realtime was set * @@ -885,8 +898,32 @@ 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 (!zalloc_cpumask_var(&mask, GFP_KERNEL)) { + on_each_cpu(retrigger_next_event, NULL, 1); + goto set_timerfd; + } + + /* Avoid interrupting CPUs if possible */ + cpus_read_lock(); + for_each_online_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); + raw_spin_unlock_irqrestore(&cpu_base->lock, flags); + } + + preempt_disable(); + smp_call_function_many(mask, retrigger_next_event, NULL, 1); + preempt_enable(); + cpus_read_unlock(); + free_cpumask_var(mask); +set_timerfd: #endif timerfd_clock_was_set(); }