From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <41D471FB.1060805@yahoo.com.au> Date: Fri, 31 Dec 2004 08:24:11 +1100 From: Nick Piggin MIME-Version: 1.0 Subject: Re: [RFC][PATCH 0/10] alternate 4-level page tables patches References: <20041221093628.GA6231@wotan.suse.de> <20041221201927.GD15643@wotan.suse.de> <41C8B678.40007@yahoo.com.au> <20041222103800.GC15894@wotan.suse.de> <41C9582D.5020201@yahoo.com.au> <20041222180748.GB9339@wotan.suse.de> In-Reply-To: <20041222180748.GB9339@wotan.suse.de> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Andi Kleen Cc: Linus Torvalds , Hugh Dickins , Linux Memory Management , Andrew Morton List-ID: Andi Kleen wrote: > On Wed, Dec 22, 2004 at 10:19:09PM +1100, Nick Piggin wrote: > >>But the advantages I see in the source code are a) pud folding matches >>exactly >>how pmd folding was done on 2 level architectures, and b) it doesn't touch >>either of the "business ends" of the page table structure (ie. top most or >>bottom most levels). I think these two points give some (if only slight) >>advantage in maintainability and consistency. > > > Sure, but when it's merged then pml4_t (or p_t) would be > the "business end", so it doesn't make much difference longer term. > After all future linux coders will not really care what was in the > past, just what is in the code at the time they hack on it. > Yeah OK, raw-code wise the pml4 patch isn't much different. But the conceptual intrusiveness of having the folding 'magic' in the top level page table is a bit higher. Also, pml4 does have some implementation intrusiveness by introducing a new _way_ of folding the table, whereas pud folds in the same manner as pmd. > > >>If I can get the bulk of the architectures changed and tested, the arch >>maintainers don't kick up too much fuss, it has a relatively trouble free >>run >>in -mm, and Andrew and Linus are still happy to merge before 2.6.11, would >>you >>be OK with the pud version (in principle)? > > > I can't say I'm very enthusiastic about it (but more due to scheduling > issues than technical issues). I don't see anything wrong with them by itself, > but I also don't think they have any particular advantages over the > pml4 version. But in the end the main thing I care about is that > 4 level pagetables get in in some form, where exactly the > new level is added and how it is named is secondary. > So long as you are not completely against it, that is a good start ;) > I would prefer if it happened sooner though because the work > is not finished (the optimized walking is still needed), > and i've been just waiting for getting merged and settled > down a bit before continuing. > Yeah sure. I can also try to help with that (regardless of which patch is merged). -- 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