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=-6.2 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 9ADC1C11F6A for ; Thu, 1 Jul 2021 21:06:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7F69F61410 for ; Thu, 1 Jul 2021 21:06:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234349AbhGAVJG (ORCPT ); Thu, 1 Jul 2021 17:09:06 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:33987 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234158AbhGAVI4 (ORCPT ); Thu, 1 Jul 2021 17:08:56 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1625173585; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc; bh=k2ppV8GaZxnsF/ngB3ZEy193ksSbr0wzGfXo/mHZEtI=; b=MmJoaE9rWHyouaOyenfefg2HH/IBp1dfedJWJtpiooCKzSdZfolVtLB2Ea3XsYB+viAO3e QnKCRL3ToneR86QMwJ87G+OTO9f5ZQnPRuyjDXRmZhyXbWQ2szr/saD/NH5sEMXja53Cy/ UrjjwCD9alQyN8mHoeCeNXjygRik6xM= 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-341-uRCrKSC1OhyiC-gK5MIh0g-1; Thu, 01 Jul 2021 17:06:24 -0400 X-MC-Unique: uRCrKSC1OhyiC-gK5MIh0g-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 ED00CCC622; Thu, 1 Jul 2021 21:06:22 +0000 (UTC) Received: from fuller.cnet (ovpn-112-6.gru2.redhat.com [10.97.112.6]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 08D0C60BD9; Thu, 1 Jul 2021 21:06:16 +0000 (UTC) Received: by fuller.cnet (Postfix, from userid 1000) id 1CDF34179B8D; Thu, 1 Jul 2021 18:06:06 -0300 (-03) Message-ID: <20210701210336.358118649@fuller.cnet> User-Agent: quilt/0.66 Date: Thu, 01 Jul 2021 18:03:36 -0300 From: Marcelo Tosatti To: linux-kernel@vger.kernel.org Cc: Christoph Lameter , Thomas Gleixner , Frederic Weisbecker , Juri Lelli , Nitesh Lal Subject: [patch 0/5] optionally sync per-CPU vmstats counter on return to userspace X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The logic to disable vmstat worker thread, when entering nohz full, does not cover all scenarios. For example, it is possible for the following to happen: 1) enter nohz_full, which calls refresh_cpu_vm_stats, syncing the stats. 2) app runs mlock, which increases counters for mlock'ed pages. 3) start -RT loop Since refresh_cpu_vm_stats from nohz_full logic can happen _before_ the mlock, vmstat shepherd can restart vmstat worker thread on the CPU in question. To fix this, optionally sync the vmstat counters when returning from userspace, controllable by a new "vmstat_sync" isolcpus flags (default off). See individual patches for details.