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=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 76723C1B0F1 for ; Tue, 19 Jun 2018 22:17:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2BA8320693 for ; Tue, 19 Jun 2018 22:17:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="VyduXeSb" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2BA8320693 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965061AbeFSWRY (ORCPT ); Tue, 19 Jun 2018 18:17:24 -0400 Received: from mail-pf0-f193.google.com ([209.85.192.193]:37919 "EHLO mail-pf0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965030AbeFSWRU (ORCPT ); Tue, 19 Jun 2018 18:17:20 -0400 Received: by mail-pf0-f193.google.com with SMTP id b74-v6so538670pfl.5 for ; Tue, 19 Jun 2018 15:17:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=LUaeA5UqA6g3K9/+Of32uFu1Tldu5MqCLKS9h5ShqEI=; b=VyduXeSb1HK0m13P/koAV1c09XiZ4V08wIGO+ZTkTsZc312GKvGZ1pBuAPKYuZDed5 fho4hlCMj9StRlnPl2clfw4lXfIK3MXWVifACLvC/H5NYSRDdE/YtUDMbEokm2fJLxxN ZiLctKvqf2zwBiwp+ySPaXI7E5LfVYZoJJl3NHl8XtoE+7Z+88lL8msGnNmVVcM3cbi+ YT0ZbbJISmTY8Xnb/m0dOkRJZZ3ARy1kXGSDorWp2a9yuCUWwQRwvfslcbJ4MhCyAeyG BFhrN8pk9yQ4ZZCjdqzdfrP9sCyQPJ1HwBfS/r6o615HNyqTkh111cOEYeiqIHvbEdWL bBJg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=LUaeA5UqA6g3K9/+Of32uFu1Tldu5MqCLKS9h5ShqEI=; b=O23go3plYYfCdAgng3zK//ej7wHM8lmxJSEGqSfjgqrgRbZ5u7X4BP5cJ4QLaSFdD4 90G4RkTXPFPihIZwinEWXv+J8YAu5lo9SfYyfqTCiI/aa5ptYeaDZ6r4tCxr1kCyqP2w oeLkNdjP07M1FOMpbsyX65znIeh7pDpILMVrtNZNTSgIMLn4LAyAN4LrIXHIjCMsGUZd rQDJeWNT5nGQ1rfsrK86GlqbRxDMvTqeF1gWl0LQfoPxhlxDILNCqA95LHC+cqLpDIKf GmrPHWOGrdCbRwUA+hgDzMs0xdiMnag4yrpJMZVPSJpIeGrQ7WhF0Ob0yHa5yig8Msuo uusQ== X-Gm-Message-State: APt69E3axyR2j2GdAIlP+f691wOPO6VYh9m8pTm4u+hgSkGCbkeNyUvY AF8sFqwLIZtmas51rCMAACk= X-Google-Smtp-Source: ADUXVKLS9ovD65wJgqxM9sexzkAgKbBqndQXvW0lE811oG6WGCtjL5dT7ej4fjYhOxOIryrThIGXKQ== X-Received: by 2002:a62:d09:: with SMTP id v9-v6mr19706466pfi.163.1529446639801; Tue, 19 Jun 2018 15:17:19 -0700 (PDT) Received: from [10.2.101.129] ([208.91.2.2]) by smtp.gmail.com with ESMTPSA id s14-v6sm778426pfh.116.2018.06.19.15.17.18 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 19 Jun 2018 15:17:18 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 11.4 \(3445.8.2\)) Subject: Re: [RFC v2 PATCH 2/2] mm: mmap: zap pages with read mmap_sem for large mapping From: Nadav Amit In-Reply-To: <1529364856-49589-3-git-send-email-yang.shi@linux.alibaba.com> Date: Tue, 19 Jun 2018 15:17:16 -0700 Cc: Michal Hocko , Matthew Wilcox , ldufour@linux.vnet.ibm.com, Andrew Morton , Peter Zijlstra , Ingo Molnar , acme@kernel.org, alexander.shishkin@linux.intel.com, jolsa@redhat.com, namhyung@kernel.org, "open list:MEMORY MANAGEMENT" , linux-kernel@vger.kernel.org Content-Transfer-Encoding: 7bit Message-Id: <3DDF2672-FCC4-4387-9624-92F33C309CAE@gmail.com> References: <1529364856-49589-1-git-send-email-yang.shi@linux.alibaba.com> <1529364856-49589-3-git-send-email-yang.shi@linux.alibaba.com> To: Yang Shi X-Mailer: Apple Mail (2.3445.8.2) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org at 4:34 PM, Yang Shi wrote: > When running some mmap/munmap scalability tests with large memory (i.e. >> 300GB), the below hung task issue may happen occasionally. > > INFO: task ps:14018 blocked for more than 120 seconds. > Tainted: G E 4.9.79-009.ali3000.alios7.x86_64 #1 > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this > message. > ps D 0 14018 1 0x00000004 > (snip) > > Zapping pages is the most time consuming part, according to the > suggestion from Michal Hock [1], zapping pages can be done with holding > read mmap_sem, like what MADV_DONTNEED does. Then re-acquire write > mmap_sem to manipulate vmas. Does munmap() == MADV_DONTNEED + munmap() ? For example, what happens with userfaultfd in this case? Can you get an extra #PF, which would be visible to userspace, before the munmap is finished? In addition, would it be ok for the user to potentially get a zeroed page in the time window after the MADV_DONTNEED finished removing a PTE and before the munmap() is done? Regards, Nadav