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 35E77C433E0 for ; Thu, 28 Jan 2021 20:26:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DE0CF64DDE for ; Thu, 28 Jan 2021 20:26:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231468AbhA1U0C (ORCPT ); Thu, 28 Jan 2021 15:26:02 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:46432 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231464AbhA1UZ3 (ORCPT ); Thu, 28 Jan 2021 15:25:29 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1611865442; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc; bh=54I4OH5A+bejmVro9oo5kF+/gWENP7z9qc/XX1w/vI8=; b=TklPzJUS2uG0gQQ/tpBs12zX2huQLkaFuCWZLGm9RoXnnm1xQOUGzXdyBEqEx+OC9lxO4m N8RANwFF1Nicn/SD94sHIaGVjATN2EnVCTgkH9hSheD6jBXMxLub+RZy/bTxYfNyepIIVs VFfv1kwV7Oxhp7Xn5PTGwBAwfgIho9M= 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-245-c6duDxXFNa-eUeXCLFTQjQ-1; Thu, 28 Jan 2021 15:24:00 -0500 X-MC-Unique: c6duDxXFNa-eUeXCLFTQjQ-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 760DB80ED8E; Thu, 28 Jan 2021 20:23:59 +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 2810A1F45D; Thu, 28 Jan 2021 20:23:59 +0000 (UTC) Received: by fuller.cnet (Postfix, from userid 1000) id 0ED98416D87F; Thu, 28 Jan 2021 17:23:35 -0300 (-03) Message-ID: <20210128202134.608115362@fuller.cnet> User-Agent: quilt/0.66 Date: Thu, 28 Jan 2021 17:21:34 -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 (v5) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 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. v5: actually replace superfluous rcu_read_lock with lockdep_assert v4: only IPI if the remote task is on the remote runqueue (PeterZ/Frederic) v3: replace superfluous rcu_read_lock with lockdep_assert (PeterZ)