From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 4 Apr 2003 22:53:05 -0500 (EST) From: Rik van Riel Subject: Re: objrmap and vmtruncate In-Reply-To: <20030404150744.7e213331.akpm@digeo.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: Andrea Arcangeli , Ingo Molnar , hugh@veritas.com, dmccr@us.ibm.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Fri, 4 Apr 2003, Andrew Morton wrote: > I think that's right - the system call is very specialised and is > targeted at solving problems which have been encountered in a small > number of applications, but important ones. > > Right now, I do not feel that we are going to be able to come up with an > acceptably simple VM which has both nonlinear mappings and objrmap. This is ok if we make nonlinear VMAs automatically mlocked, meaning they don't need reverse mapping at all. If you need the space saving from nonlinear VMAs, you also need to save the space of any kind of reverse mapping scheme, even a mythical nonlinear object one (just think about the minimum amount of data you need to store). IMHO it'd be fair to limit nonlinear VMAs to the set of very specialised applications that need it (Oracle, DB2, anything else?) and impose some limitations on the functionality so the main part of the VM stay sane. Rik -- 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: aart@kvack.org