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=-0.8 required=3.0 tests=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 04DEEC3279B for ; Sat, 30 Jun 2018 03:15:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A8CE927F3D for ; Sat, 30 Jun 2018 03:15:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A8CE927F3D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.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 S1755629AbeF3DPu (ORCPT ); Fri, 29 Jun 2018 23:15:50 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:33042 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755530AbeF3DPt (ORCPT ); Fri, 29 Jun 2018 23:15:49 -0400 Received: from localhost.localdomain (c-24-4-125-7.hsd1.ca.comcast.net [24.4.125.7]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 6F2C2C49; Sat, 30 Jun 2018 03:15:48 +0000 (UTC) Date: Fri, 29 Jun 2018 20:15:47 -0700 From: Andrew Morton To: Yang Shi Cc: mhocko@kernel.org, willy@infradead.org, ldufour@linux.vnet.ibm.com, 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 4/5] mm: mmap: zap pages with read mmap_sem for large mapping Message-Id: <20180629201547.5322cfc4b52d19a0443daec2@linux-foundation.org> In-Reply-To: <084aeccb-2c54-2299-8bf0-29a10cc0186e@linux.alibaba.com> References: <1530311985-31251-1-git-send-email-yang.shi@linux.alibaba.com> <1530311985-31251-5-git-send-email-yang.shi@linux.alibaba.com> <20180629183501.9e30c26135f11853245c56c7@linux-foundation.org> <084aeccb-2c54-2299-8bf0-29a10cc0186e@linux.alibaba.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 29 Jun 2018 19:28:15 -0700 Yang Shi wrote: > > > > we're adding a bunch of code to 32-bit kernels which will never be > > executed. > > > > I'm thinking it would be better to be much more explicit with "#ifdef > > CONFIG_64BIT" in this code, rather than relying upon the above magic. > > > > But I tend to think that the fact that we haven't solved anything on > > locked vmas or on uprobed mappings is a shostopper for the whole > > approach :( > > I agree it is not that perfect. But, it still could improve the most use > cases. Well, those unaddressed usecases will need to be fixed at some point. What's our plan for that? Would one of your earlier designs have addressed all usecases? I expect the dumb unmap-a-little-bit-at-a-time approach would have? > For the locked vmas and hugetlb vmas, unmapping operations need modify > vm_flags. But, I'm wondering we might be able to separate unmap and > vm_flags update. Because we know they will be unmapped right away, the > vm_flags might be able to be updated in write mmap_sem critical section > before the actual unmap is called or after it. This is just off the top > of my head. > > For uprobed mappings, I'm not sure how vital it is to this case. > > Thanks, > Yang > > >