Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261692AbTIJKHj (ORCPT ); Wed, 10 Sep 2003 06:07:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261738AbTIJKHj (ORCPT ); Wed, 10 Sep 2003 06:07:39 -0400 Received: from pix-525-pool.redhat.com ([66.187.233.200]:26156 "EHLO devserv.devel.redhat.com") by vger.kernel.org with ESMTP id S261692AbTIJKHg (ORCPT ); Wed, 10 Sep 2003 06:07:36 -0400 Date: Wed, 10 Sep 2003 12:07:29 +0200 From: Arjan van de Ven To: Jamie Lokier Cc: Arjan van de Ven , Luca Veraldi , alexander.riesen@synopsys.COM, linux-kernel Subject: Re: Efficient IPC mechanism on Linux Message-ID: <20030910120729.C14352@devserv.devel.redhat.com> References: <00f201c376f8$231d5e00$beae7450@wssupremo> <20030909175821.GL16080@Synopsys.COM> <001d01c37703$8edc10e0$36af7450@wssupremo> <20030910064508.GA25795@Synopsys.COM> <015601c3777c$8c63b2e0$5aaf7450@wssupremo> <1063185795.5021.4.camel@laptop.fenrus.com> <20030910095255.GA21313@mail.jlokier.co.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i In-Reply-To: <20030910095255.GA21313@mail.jlokier.co.uk>; from jamie@shareable.org on Wed, Sep 10, 2003 at 10:52:55AM +0100 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1196 Lines: 25 On Wed, Sep 10, 2003 at 10:52:55AM +0100, Jamie Lokier wrote: > Arjan van de Ven wrote: > > > The overhead implied by a memcpy() is the same, in the oder of magnitude, > > > ***whatever*** kernel version you can develop. > > > > yes a copy of a page is about 3000 to 4000 cycles on an x86 box in the > > uncached case. A pagetable operation (like the cpu setting the accessed > > or dirty bit) is in that same order I suspect (maybe half this, but not > > a lot less). Changing pagetable content is even more because all the > > tlb's and internal cpu state will need to be flushed... which is also a > > microcode operation for the cpu. And it's deadly in an SMP environment. > > I have just done a measurement on a 366MHz PII Celeron This test is sort of the worst case against my argument: 1) It's a cpu with low memory bandwidth 2) It's a 1 CPU system 3) It's a pII not pIV; the pII is way more efficient cycle wise for pagetable operations - 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/