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=-1.0 required=3.0 tests=MAILING_LIST_MULTI autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by aws-us-west-2-korg-lkml-1.web.codeaurora.org (Postfix) with ESMTP id 96549C004E4 for ; Wed, 13 Jun 2018 08:37:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5420D208AF for ; Wed, 13 Jun 2018 08:37:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5420D208AF 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 S934750AbeFMIhN (ORCPT ); Wed, 13 Jun 2018 04:37:13 -0400 Received: from mx2.suse.de ([195.135.220.15]:45984 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933912AbeFMIhK (ORCPT ); Wed, 13 Jun 2018 04:37:10 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (charybdis-ext-too.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 08B4CAD88; Wed, 13 Jun 2018 08:37:09 +0000 (UTC) Date: Wed, 13 Jun 2018 10:37:07 +0200 From: Michal Hocko To: Vlastimil Babka Cc: Jason Baron , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Joonsoo Kim , Mel Gorman , "Kirill A. Shutemov" , linux-api@vger.kernel.org, emunson@mgebm.net Subject: Re: [PATCH] mm/madvise: allow MADV_DONTNEED to free memory that is MLOCK_ONFAULT Message-ID: <20180613083707.GE13364@dhcp22.suse.cz> References: <1528484212-7199-1-git-send-email-jbaron@akamai.com> <20180611072005.GC13364@dhcp22.suse.cz> <4c4de46d-c55a-99a8-469f-e1e634fb8525@akamai.com> <20180611150330.GQ13364@dhcp22.suse.cz> <775adf2d-140c-1460-857f-2de7b24bafe7@akamai.com> <20180612074646.GS13364@dhcp22.suse.cz> <5a9398f4-453c-5cb5-6bbc-f20c3affc96a@akamai.com> <0daccb7c-f642-c5ce-ca7a-3b3e69025a1e@suse.cz> <20180613071552.GD13364@dhcp22.suse.cz> <5eb9a018-d5ac-5732-04f1-222c343b840a@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5eb9a018-d5ac-5732-04f1-222c343b840a@suse.cz> User-Agent: Mutt/1.9.5 (2018-04-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 13-06-18 09:51:23, Vlastimil Babka wrote: > On 06/13/2018 09:15 AM, Michal Hocko wrote: > > On Wed 13-06-18 08:32:19, Vlastimil Babka wrote: [...] > >> I think more concerning than guaranteeing no later major fault is > >> possible data loss, e.g. replacing data with zero-filled pages. > > > > But MADV_DONTNEED is an explicit call for data loss. Or do I miss your > > point? > > My point is that if somebody is relying on MADV_DONTNEED not affecting > mlocked pages, the consequences will be unexpected data loss, not just > extra page faults. OK, I see your point now. I would consider this an application bug though. Calling MADV_DONTNEED and wondering that the content is gone is, ehm, questionable at best. Why would anybody do that in the first place? Anyway, I think that we cannot change the behavior because of mlockall semantic as mentioned earlier. -- Michal Hocko SUSE Labs