From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 20 Dec 2004 19:56:36 -0800 (PST) From: Linus Torvalds Subject: Re: [RFC][PATCH 0/10] alternate 4-level page tables patches In-Reply-To: Message-ID: References: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Hugh Dickins Cc: Nick Piggin , Andi Kleen , Linux Memory Management , Andrew Morton List-ID: On Mon, 20 Dec 2004, Linus Torvalds wrote: > > (It may be _possible_ to avoid the warnings by just making "pud_t" and > "pmd_t" be the same type for such architectures, and just allowing > _mixing_ of three-level and four-level accesses. I have to say that I > consider that pretty borderline programming practice though). Actually, I notice that this is exactly what you did, sorry for not being more careful about reading your defines. Thinking some more about it, I don't much like the "mixing" of 3-level and 4-level things, but since the only downside is a lack of type-safety for the 4-level case (ie you can get it wrong without getting any warning), and since that type safety _does_ exist in the case where the four levels are actually used, I think it's ok. It would be bad if the architecture that supported 4level page tables was really rare and broken (so that mistakes would happen and not get noticed for a while), but I suspect x86-64 by now is probably the second- or third-most used architecture, so it's not like the lack of type safety on other architectures where it doesn't matter would be a huge maintenance problem. Color me convinced. Nick, can you see if such a patch is possible? I'll test ppc64 still working.. Linus -- 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