From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f53.google.com (mail-pa0-f53.google.com [209.85.220.53]) by kanga.kvack.org (Postfix) with ESMTP id A6E136B0254 for ; Fri, 13 Nov 2015 02:03:38 -0500 (EST) Received: by pasz6 with SMTP id z6so94531455pas.2 for ; Thu, 12 Nov 2015 23:03:38 -0800 (PST) Received: from lgeamrelo12.lge.com (LGEAMRELO12.lge.com. [156.147.23.52]) by mx.google.com with ESMTPS id fk1si25482976pad.35.2015.11.12.23.03.37 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 12 Nov 2015 23:03:37 -0800 (PST) Date: Fri, 13 Nov 2015 16:03:56 +0900 From: Minchan Kim Subject: Re: [PATCH v3 01/17] mm: support madvise(MADV_FREE) Message-ID: <20151113070356.GG5235@bbox> References: <1447302793-5376-1-git-send-email-minchan@kernel.org> <1447302793-5376-2-git-send-email-minchan@kernel.org> <564421DA.9060809@gmail.com> <20151113061511.GB5235@bbox> <56458056.8020105@gmail.com> <20151113063802.GF5235@bbox> <56458720.4010400@gmail.com> MIME-Version: 1.0 In-Reply-To: <56458720.4010400@gmail.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline Sender: owner-linux-mm@kvack.org List-ID: To: Daniel Micay Cc: Andy Lutomirski , Andrew Morton , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , Michael Kerrisk , Linux API , Hugh Dickins , Johannes Weiner , Rik van Riel , Mel Gorman , KOSAKI Motohiro , Jason Evans , "Kirill A. Shutemov" , Shaohua Li , Michal Hocko , yalin wang On Fri, Nov 13, 2015 at 01:45:52AM -0500, Daniel Micay wrote: > > And now I am thinking if we use access bit, we could implment MADV_FREE_UNDO > > easily when we need it. Maybe, that's what you want. Right? > > Yes, but why the access bit instead of the dirty bit for that? It could > always be made more strict (i.e. access bit) in the future, while going > the other way won't be possible. So I think the dirty bit is really the > more conservative choice since if it turns out to be a mistake it can be > fixed without a backwards incompatible change. Absolutely true. That's why I insist on dirty bit until now although I didn't tell the reason. But I thought you wanted to change for using access bit for the future, too. It seems MADV_FREE start to bloat over and over again before knowing real problems and usecases. It's almost same situation with volatile ranges so I really want to stop at proper point which maintainer should decide, I hope. Without it, we will make the feature a lot heavy by just brain storming and then causes lots of churn in MM code without real bebenfit It would be very painful for us. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org