Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 9 Nov 2001 02:17:00 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 9 Nov 2001 02:16:44 -0500 Received: from pizda.ninka.net ([216.101.162.242]:10882 "EHLO pizda.ninka.net") by vger.kernel.org with ESMTP id ; Fri, 9 Nov 2001 02:16:38 -0500 Date: Thu, 08 Nov 2001 23:16:32 -0800 (PST) Message-Id: <20011108.231632.18311891.davem@redhat.com> To: ak@suse.de Cc: anton@samba.org, mingo@elte.hu, linux-kernel@vger.kernel.org Subject: Re: speed difference between using hard-linked and modular drives? From: "David S. Miller" In-Reply-To: <20011109073946.A19373@wotan.suse.de> In-Reply-To: <20011109064540.A13498@wotan.suse.de> <20011108.220444.95062095.davem@redhat.com> <20011109073946.A19373@wotan.suse.de> X-Mailer: Mew version 2.0 on Emacs 21.0 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org From: Andi Kleen Date: Fri, 9 Nov 2001 07:39:46 +0100 I'm assuming that walking on average 5-10 pages on a lookup is not too big a deal, especially when you use prefetch for the list walk. Oh no, not this again... It _IS_ a big deal. Fetching _ONE_ hash chain cache line is always going to be cheaper than fetching _FIVE_ to _TEN_ page struct cache lines while walking the list. Even if prefetch would kill all of this overhead (sorry, it won't), it is _DUMB_ and _STUPID_ to bring those _FIVE_ to _TEN_ cache lines into the processor just to lookup _ONE_ page. Franks a lot, 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 More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/