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=-6.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 1729BC433E0 for ; Thu, 28 Jan 2021 18:53:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DD10F64E25 for ; Thu, 28 Jan 2021 18:53:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232620AbhA1SwT (ORCPT ); Thu, 28 Jan 2021 13:52:19 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:21319 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232334AbhA1SqO (ORCPT ); Thu, 28 Jan 2021 13:46:14 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1611859487; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc; bh=d9DCyUiqhGMRjufRtGd0K7buDIsKCn12kYp0ACHugHk=; b=AnoCcZZOer0klEkXLaMo2Uh1Z2ECrFSRbLEITso+UzG8e+b+aYJIL3qR4UaNzGpDnb6vkY LOTHeRwKOu+TOQi1rY15Jj6WFNmZz0ogzebLd4IJEKnK983fWbPf+EpQTV2eUqeO+NNaX/ dBTuwWsU/UZjZKyvniIdXB85LIk/WFs= 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-63-B7Pqbyu0NQK69H4Y2ndRqg-1; Thu, 28 Jan 2021 13:44:44 -0500 X-MC-Unique: B7Pqbyu0NQK69H4Y2ndRqg-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id EB13A803622; Thu, 28 Jan 2021 18:44:42 +0000 (UTC) Received: from fuller.cnet (ovpn-112-2.gru2.redhat.com [10.97.112.2]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B07EE5D9F4; Thu, 28 Jan 2021 18:44:42 +0000 (UTC) Received: by fuller.cnet (Postfix, from userid 1000) id E1141416D87F; Thu, 28 Jan 2021 15:44:20 -0300 (-03) Message-ID: <20210128184048.287626221@fuller.cnet> User-Agent: quilt/0.66 Date: Thu, 28 Jan 2021 15:40:48 -0300 From: Marcelo Tosatti To: Peter Zijlstra , Frederic Weisbecker Cc: linux-kernel@vger.kernel.org Subject: [patch 0/3] nohz_full: only wakeup target CPUs when notifying new tick dependency (v4) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When enabling per-CPU posix timers, an IPI to nohz_full CPUs might be performed (to re-read the dependencies and possibly not re-enter nohz_full on a given CPU). A common case is for applications that run on nohz_full= CPUs to not use POSIX timers (eg DPDK). This patch changes the notification to only IPI the target CPUs where the task(s) whose tick dependencies are being updated are executing. This reduces interruptions to nohz_full= CPUs. v4: only IPI if the remote task is on the remote runqueue (PeterZ/Frederic) v3: replace superfluous rcu_read_lock with lockdep_assert (PeterZ)