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=-2.5 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT 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 559C5C3279B for ; Mon, 2 Jul 2018 13:39:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0F10C2524D for ; Mon, 2 Jul 2018 13:39:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0F10C2524D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org 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 S1752228AbeGBNj4 (ORCPT ); Mon, 2 Jul 2018 09:39:56 -0400 Received: from mx2.suse.de ([195.135.220.15]:45966 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751912AbeGBNjz (ORCPT ); Mon, 2 Jul 2018 09:39:55 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 031C1AD12; Mon, 2 Jul 2018 13:39:54 +0000 (UTC) Date: Mon, 2 Jul 2018 15:39:53 +0200 From: Michal Hocko To: Yang Shi Cc: willy@infradead.org, ldufour@linux.vnet.ibm.com, akpm@linux-foundation.org, peterz@infradead.org, mingo@redhat.com, acme@kernel.org, alexander.shishkin@linux.intel.com, jolsa@redhat.com, namhyung@kernel.org, tglx@linutronix.de, hpa@zytor.com, linux-mm@kvack.org, x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC v3 PATCH 0/5] mm: zap pages with read mmap_sem in munmap for large mapping Message-ID: <20180702133953.GV19043@dhcp22.suse.cz> References: <1530311985-31251-1-git-send-email-yang.shi@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1530311985-31251-1-git-send-email-yang.shi@linux.alibaba.com> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat 30-06-18 06:39:40, Yang Shi wrote: > > Background: > Recently, when we ran some vm scalability tests on machines with large memory, > we ran into a couple of mmap_sem scalability issues when unmapping large memory > space, please refer to https://lkml.org/lkml/2017/12/14/733 and > https://lkml.org/lkml/2018/2/20/576. > > > History: > Then akpm suggested to unmap large mapping section by section and drop mmap_sem > at a time to mitigate it (see https://lkml.org/lkml/2018/3/6/784). > > V1 patch series was submitted to the mailing list per Andrew’s suggestion > (see https://lkml.org/lkml/2018/3/20/786). Then I received a lot great feedback > and suggestions. > > Then this topic was discussed on LSFMM summit 2018. In the summit, Michal Hock > suggested (also in the v1 patches review) to try "two phases" approach. Zapping > pages with read mmap_sem, then doing via cleanup with write mmap_sem (for > discussion detail, see https://lwn.net/Articles/753269/) The cover letter should really describe your approach to the problem. But there is none here. -- Michal Hocko SUSE Labs