Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 28 Dec 2000 19:02:31 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 28 Dec 2000 19:02:22 -0500 Received: from pizda.ninka.net ([216.101.162.242]:10625 "EHLO pizda.ninka.net") by vger.kernel.org with ESMTP id ; Thu, 28 Dec 2000 19:02:03 -0500 Date: Thu, 28 Dec 2000 15:14:56 -0800 Message-Id: <200012282314.PAA01997@pizda.ninka.net> From: "David S. Miller" To: ak@suse.de CC: ak@suse.de, torvalds@transmeta.com, marcelo@conectiva.com.br, linux-kernel@vger.kernel.org In-Reply-To: <20001229001721.B25388@gruyere.muc.suse.de> (message from Andi Kleen on Fri, 29 Dec 2000 00:17:21 +0100) Subject: Re: test13-pre5 In-Reply-To:

<20001228231722.A24875@gruyere.muc.suse.de> <200012282233.OAA01433@pizda.ninka.net> <20001228235836.A25388@gruyere.muc.suse.de> <200012282254.OAA01772@pizda.ninka.net> <20001229001721.B25388@gruyere.muc.suse.de> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Date: Fri, 29 Dec 2000 00:17:21 +0100 From: Andi Kleen On Thu, Dec 28, 2000 at 02:54:52PM -0800, David S. Miller wrote: > To make things like "page - mem_map" et al. use shifts instead of > expensive multiplies... I thought that is what ->index is for ? It is for the page cache identity Andi... you know, page_hash(mapping, index)... And the add/sub/shift expansion of a multiply/divide by constant even in its' most optimal form is often not trivial, it is something on the order of 7 instructions with waitq debugging enabled last time I checked. Later, David S. Miller davem@redhat.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/