Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 31 Jan 2002 13:34:10 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 31 Jan 2002 13:34:01 -0500 Received: from neon-gw-l3.transmeta.com ([63.209.4.196]:64773 "EHLO neon-gw.transmeta.com") by vger.kernel.org with ESMTP id ; Thu, 31 Jan 2002 13:33:49 -0500 Date: Thu, 31 Jan 2002 10:32:35 -0800 (PST) From: Linus Torvalds To: Andrea Arcangeli cc: Rik van Riel , Momchil Velikov , John Stoffel , Subject: Re: [PATCH] Radix-tree pagecache for 2.5 In-Reply-To: <20020131190202.I1309@athlon.random> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 31 Jan 2002, Andrea Arcangeli wrote: > > > > The radix tree is basically O(1), because the maximum depth of a 7-bit > > radix tree is just 5. The index is only a 32-bit number. > > then it will break on archs with more ram than 1<<(32+PAGE_CACHE_SHIFT). NO. The radix tree is an index lookup mechanism. The index is 32 bits. That's true regardless of how much RAM you have. > Also there must be some significant memory overhead that can be > triggered with a certain layout of pages, in some configuration it > should take much more ram than the hashtable if I understood well how it > works. Considering that the radix tree can _remove_ 8 bytes per "struct page", I suspect you potentially win more memory than you lose. Linus - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/