From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: Multicast Routing Kernel option? Date: Fri, 15 Aug 2008 16:13:24 +0200 Message-ID: <87tzdmxt6j.fsf@basil.nowhere.org> References: <124178.76775.qm@web31502.mail.mud.yahoo.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, Daniel Ng To: imipak@yahoo.com Return-path: Received: from one.firstfloor.org ([213.235.205.2]:42754 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753933AbYHOON1 (ORCPT ); Fri, 15 Aug 2008 10:13:27 -0400 In-Reply-To: <124178.76775.qm@web31502.mail.mud.yahoo.com> (Jonathan Day's message of "Fri, 15 Aug 2008 01:41:51 -0700 (PDT)") Sender: netdev-owner@vger.kernel.org List-ID: Jonathan Day writes: > They could, I guess, but context switches are expensive (think 20ms > from kernel to user, and same in reverse) 40ms for a system call? That would be really horrible if it really were that slow. Fortunately it's not. A Core2 (Merom) here can do a very simple system call roundtrip (getppid()) in ~570 cycles, that is at 2Ghz less than 300ns. You are roughly 5 orders of magnitude off. -Andi