From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758827AbZEFRBJ (ORCPT ); Wed, 6 May 2009 13:01:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754547AbZEFRAz (ORCPT ); Wed, 6 May 2009 13:00:55 -0400 Received: from mx2.redhat.com ([66.187.237.31]:50086 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753559AbZEFRAy (ORCPT ); Wed, 6 May 2009 13:00:54 -0400 Message-ID: <4A01C1AD.9060802@redhat.com> Date: Wed, 06 May 2009 19:58:21 +0300 From: Izik Eidus User-Agent: Mozilla-Thunderbird 2.0.0.19 (X11/20090103) MIME-Version: 1.0 To: Hugh Dickins CC: Rik van Riel , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, aarcange@redhat.com, chrisw@redhat.com, alan@lxorguk.ukuu.org.uk, device@lanana.org, linux-mm@kvack.org, nickpiggin@yahoo.com.au Subject: Re: [PATCH 3/6] ksm: change the KSM_REMOVE_MEMORY_REGION ioctl. References: <1241475935-21162-1-git-send-email-ieidus@redhat.com> <1241475935-21162-2-git-send-email-ieidus@redhat.com> <1241475935-21162-3-git-send-email-ieidus@redhat.com> <1241475935-21162-4-git-send-email-ieidus@redhat.com> <4A00DF9B.1080501@redhat.com> <4A014C7B.9080702@redhat.com> <4A01AC5E.6000906@redhat.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hugh Dickins wrote: > On Wed, 6 May 2009, Izik Eidus wrote: > >> We can first start with this ioctl interface, later when we add swapping to >> the pages, we can have madvice, and still (probably easily) support the ioctls >> by just calling from inside ksm the madvice functions for that specific >> address) >> >> I want to see ksm use madvice, but i believe it require some more changes to >> mm/*.c, so it probably better to start with merging it when it doesnt touch >> alot of stuff outisde ksm.c, and then to add swapping and after that add >> madvice support (when the pages are swappable, everyone can use it) >> >> What you think about that? >> > > I think it's the wrong order to follow. > > The /dev/ksm interface is fine for your use while it's out of tree, > but we want to get the user interface right when bringing it into > mainline. I recall Chris being very clear on that too. > > Changing from /dev/ksm to madvise() is not a lot of work, it's mainly > a matter of deleting code, and tidying up interfaces which would need > more work anyway (I haven't commented on your curious -EPERMs yet!). > > It doesn't involve whether you've enabled swapping or not - let's > forget the CAP_IPC_LOCK idea, and delegate that issue to limitation > via sysfs, along with the ability to limit wild overuse of the feature > - permissions on a sysfs node or something else? > > It does nudge towards making some decisions which need to be made > anyway - that tends to be what a correct interface forces upon you. > Like the issue of whether to go on covering unmapped areas or not - > though possibly we could put off that decision, if it's doc'ed > for now. > > And if it only covers mapped areas, then there will need to be a > VM_flag for it, mainly so mm can call into ksm.c when it's unmapped; > but I don't see it sinking hooks deeply into mm/*.c. > > Hugh > Ok, i give up, lets move to madvice(), i will write a patch that move the whole thing into madvice after i finish here something, but that ofcurse only if Andrea agree for the move?