From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f41.google.com (mail-pa0-f41.google.com [209.85.220.41]) by kanga.kvack.org (Postfix) with ESMTP id 2066C6B0038 for ; Mon, 7 Oct 2013 20:11:52 -0400 (EDT) Received: by mail-pa0-f41.google.com with SMTP id bj1so8062142pad.14 for ; Mon, 07 Oct 2013 17:11:51 -0700 (PDT) Date: Tue, 8 Oct 2013 09:13:06 +0900 From: Minchan Kim Subject: Re: [PATCH 05/14] vrange: Add new vrange(2) system call Message-ID: <20131008001306.GD25780@bbox> References: <1380761503-14509-1-git-send-email-john.stultz@linaro.org> <1380761503-14509-6-git-send-email-john.stultz@linaro.org> <52533C12.9090007@zytor.com> <5253404D.2030503@linaro.org> <52534331.2060402@zytor.com> <52534692.7010400@linaro.org> <525347BE.7040606@zytor.com> <525349AE.1070904@linaro.org> <52534AEC.5040403@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <52534AEC.5040403@zytor.com> Sender: owner-linux-mm@kvack.org List-ID: To: "H. Peter Anvin" Cc: John Stultz , LKML , Andrew Morton , Android Kernel Team , Robert Love , Mel Gorman , Hugh Dickins , Dave Hansen , Rik van Riel , Dmitry Adamushko , Dave Chinner , Neil Brown , Andrea Righi , Andrea Arcangeli , "Aneesh Kumar K.V" , Mike Hommey , Taras Glek , Dhaval Giani , Jan Kara , KOSAKI Motohiro , Michel Lespinasse , Rob Clark , "linux-mm@kvack.org" Hello Peter, On Mon, Oct 07, 2013 at 04:59:40PM -0700, H. Peter Anvin wrote: > On 10/07/2013 04:54 PM, John Stultz wrote: > >>> > >> And wouldn't this apply to MADV_DONTNEED just as well? Perhaps what we > >> should do is an enhanced madvise() call? > > Well, I think MADV_DONTNEED doesn't *have* do to anything at all. Its > > advisory after all. So it may immediately wipe out any data, but it may not. > > > > Those advisory semantics work fine w/ VRANGE_VOLATILE. However, > > VRANGE_NONVOLATILE is not quite advisory, its telling the system that it > > requires the memory at the specified range to not be volatile, and we > > need to correctly inform userland how much was changed and if any of the > > memory we did change to non-volatile was purged since being set volatile. > > > > In that way it is sort of different from madvise. Some sort of an > > madvise2 could be done, but then the extra purge state argument would be > > oddly defined for any other mode. > > > > Is your main concern here just wanting to have a zero-fill mode with > > volatile ranges? Or do you really want to squeeze this in to the madvise > > call interface? > > The point is that MADV_DONTNEED is very similar in that sense, > especially if allowed to be lazy. It makes a lot of sense to permit > both scrubbing modes orthogonally. > > The point you're making has to do with withdrawal of permission to flush > on demand, which is a result of having the lazy mode (ongoing > permission) and having to be able to withdraw such permission. I'm sorry I could not understand what you wanted to say. Could you elaborate a bit? Thanks. > > -0hpa > > > -- > 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 -- Kind regards, Minchan Kim -- 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