Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754742AbbHXNag (ORCPT ); Mon, 24 Aug 2015 09:30:36 -0400 Received: from mx2.suse.de ([195.135.220.15]:52886 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752904AbbHXNae (ORCPT ); Mon, 24 Aug 2015 09:30:34 -0400 Subject: Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT To: Konstantin Khlebnikov , Eric B Munson References: <1439097776-27695-1-git-send-email-emunson@akamai.com> <1439097776-27695-4-git-send-email-emunson@akamai.com> <20150812115909.GA5182@dhcp22.suse.cz> <20150819213345.GB4536@akamai.com> <20150820075611.GD4780@dhcp22.suse.cz> <20150820170309.GA11557@akamai.com> <20150821072552.GF23723@dhcp22.suse.cz> <20150821183132.GA12835@akamai.com> Cc: Michal Hocko , Andrew Morton , Jonathan Corbet , "Kirill A. Shutemov" , Linux Kernel Mailing List , dri-devel , "linux-mm@kvack.org" , Linux API From: Vlastimil Babka Message-ID: <55DB1C77.8070705@suse.cz> Date: Mon, 24 Aug 2015 15:30:31 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1377 Lines: 32 On 08/24/2015 12:17 PM, Konstantin Khlebnikov wrote: >> >> I am in the middle of implementing lock on fault this way, but I cannot >> see how we will hanlde mremap of a lock on fault region. Say we have >> the following: >> >> addr = mmap(len, MAP_ANONYMOUS, ...); >> mlock(addr, len, MLOCK_ONFAULT); >> ... >> mremap(addr, len, 2 * len, ...) >> >> There is no way for mremap to know that the area being remapped was lock >> on fault so it will be locked and prefaulted by remap. How can we avoid >> this without tracking per vma if it was locked with lock or lock on >> fault? > > remap can count filled ptes and prefault only completely populated areas. Does (and should) mremap really prefault non-present pages? Shouldn't it just prepare the page tables and that's it? > There might be a problem after failed populate: remap will handle them > as lock on fault. In this case we can fill ptes with swap-like non-present > entries to remember that fact and count them as should-be-locked pages. I don't think we should strive to have mremap try to fix the inherent unreliability of mmap (MAP_POPULATE)? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/