From owner-freebsd-net@FreeBSD.ORG Thu Oct 20 07:00:58 2005 Return-Path: X-Original-To: freebsd-net@FreeBSD.org Delivered-To: freebsd-net@FreeBSD.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 1B8CC16A41F; Thu, 20 Oct 2005 07:00:58 +0000 (GMT) (envelope-from glebius@FreeBSD.org) Received: from cell.sick.ru (cell.sick.ru [217.72.144.68]) by mx1.FreeBSD.org (Postfix) with ESMTP id 61DEF43D5A; Thu, 20 Oct 2005 07:00:57 +0000 (GMT) (envelope-from glebius@FreeBSD.org) Received: from cell.sick.ru (glebius@localhost [127.0.0.1]) by cell.sick.ru (8.13.3/8.13.3) with ESMTP id j9K70sOV097925 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Thu, 20 Oct 2005 11:00:55 +0400 (MSD) (envelope-from glebius@FreeBSD.org) Received: (from glebius@localhost) by cell.sick.ru (8.13.3/8.13.1/Submit) id j9K70sMe097924; Thu, 20 Oct 2005 11:00:54 +0400 (MSD) (envelope-from glebius@FreeBSD.org) X-Authentication-Warning: cell.sick.ru: glebius set sender to glebius@FreeBSD.org using -f Date: Thu, 20 Oct 2005 11:00:54 +0400 From: Gleb Smirnoff To: Andrew Thompson Message-ID: <20051020070054.GZ59364@cell.sick.ru> Mail-Followup-To: Gleb Smirnoff , Andrew Thompson , yar@FreeBSD.org, ru@FreeBSD.org, freebsd-net@freebsd.org References: <20051019102559.GA45909@heff.fud.org.nz> Mime-Version: 1.0 Content-Type: text/plain; charset=koi8-r Content-Disposition: inline In-Reply-To: <20051019102559.GA45909@heff.fud.org.nz> User-Agent: Mutt/1.5.6i Cc: freebsd-net@FreeBSD.org, yar@FreeBSD.org, ru@FreeBSD.org Subject: Re: vlan patch X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 20 Oct 2005 07:00:58 -0000 Andrew, On Wed, Oct 19, 2005 at 11:25:59PM +1300, Andrew Thompson wrote: A> It has always bugged me how the vlan code traverses the linked-list for A> each incoming packet to find the right ifvlan, I have this patch which A> attempts to fix this. A> A> What it does is replace the linear search for the vlan with a constant A> time lookup. It does this by allocating an array for each vlan enabled A> parent interface so the tag can be directly indexed. A> A> This has an overhead of ~16kb on 32bit, this is not too bad as there is A> usually only one physical interface when using a large number of vlans. A> A> I have measured a 1.6% pps increase with 100 vlans, and 8% with 500, and A> yes, some people use this many in production. A> A> It also has the benefit of enforcing unique vlan tags per parent which A> the current code doesn't do. Although the memory overhead is not noticable on modern i386 and amd64 PCs I don't think that we should waste so much memory. We should keep in mind the existence of embedded architectures with little memory. In most cases people use 10 - 30 VLANs. I suggest to use a hash, like it is already done in ng_vlan(4). This hash makes every sixteenth VLAN to fall into same slot. Since most people allocate VLAN ids contiguously the hash distribution should be good. Moreover, I suggest Yar and Ruslan to work together and make the hash code shared between vlan(4) and ng_vlan(4), not copy-and-pasted. -- Totus tuus, Glebius. GLEBIUS-RIPN GLEB-RIPE