Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751091AbVJBX0Y (ORCPT ); Sun, 2 Oct 2005 19:26:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751098AbVJBX0Y (ORCPT ); Sun, 2 Oct 2005 19:26:24 -0400 Received: from mx1.redhat.com ([66.187.233.31]:3721 "EHLO mx1.redhat.com") by vger.kernel.org with ESMTP id S1751091AbVJBX0Y (ORCPT ); Sun, 2 Oct 2005 19:26:24 -0400 Date: Sun, 2 Oct 2005 19:26:21 -0400 (EDT) From: Rik van Riel X-X-Sender: riel@cuia.boston.redhat.com To: Luke Kenneth Casson Leighton cc: linux-kernel@vger.kernel.org Subject: Re: what's next for the linux kernel? In-Reply-To: <20051002230545.GI6290@lkcl.net> Message-ID: References: <20051002204703.GG6290@lkcl.net> <20051002230545.GI6290@lkcl.net> 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 Content-Length: 1527 Lines: 42 On Mon, 3 Oct 2005, Luke Kenneth Casson Leighton wrote: > On Sun, Oct 02, 2005 at 05:05:42PM -0400, Rik van Riel wrote: > > Linux already has a number of scalable SMP synchronisation > > mechanisms. > > ... and you are tied in to the decisions made by the linux kernel > developers. > > whereas, if you allow something like a message-passing design (such as > in the port of the linux kernel to l4), you have the option to try out > different underlying structures - _without_ having to totally redesign > the infrastructure. Infrastructure is not what matters when it comes to SMP scalability on modern systems, since lock contention is not the primary SMP scalability problem. Due to the large latency ratio between L1/L2 cache and RAM, the biggest scalability problem is cache invalidation and cache bounces. Those are not solvable by using another underlying infrastructure - they require a reorganization of the datastructures on top, the data structures in Linux. Note that message passing is by definition less efficient than SMP synchronisation mechanisms that do not require data to be exchanged between CPUs, eg. RCU or the use of cpu-local data structures. > p.s. yes i do know of a company that has improved on SMP. SGI ? IBM ? -- All Rights Reversed - 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/