From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 18 May 2007 16:42:10 +0100 (BST) From: Hugh Dickins Subject: Re: [rfc] increase struct page size?! In-Reply-To: <20070518040854.GA15654@wotan.suse.de> Message-ID: References: <20070518040854.GA15654@wotan.suse.de> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: Linux Kernel Mailing List , Linux Memory Management List , linux-arch@vger.kernel.org List-ID: On Fri, 18 May 2007, Nick Piggin wrote: > > If we add 8 bytes to struct page on 64-bit machines, it becomes 64 bytes, > which is quite a nice number for cache purposes. > > However we don't have to let those 8 bytes go to waste: we can use them > to store the virtual address of the page, which kind of makes sense for > 64-bit, because they can likely to use complicated memory models. Sooner rather than later, don't we need those 8 bytes to expand from atomic_t to atomic64_t _count and _mapcount? Not that we really need all 64 bits of both, but I don't know how to work atomically with less. (Why do I have this sneaking feeling that you're actually wanting to stick something into the lower bits of page->virtual?) Hugh -- 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