From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030279AbWARStl (ORCPT ); Wed, 18 Jan 2006 13:49:41 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030278AbWARStl (ORCPT ); Wed, 18 Jan 2006 13:49:41 -0500 Received: from palrel10.hp.com ([156.153.255.245]:33994 "EHLO palrel10.hp.com") by vger.kernel.org with ESMTP id S1030275AbWARStk (ORCPT ); Wed, 18 Jan 2006 13:49:40 -0500 Date: Wed, 18 Jan 2006 10:49:45 -0800 From: Grant Grundler To: Sean Hefty Cc: Roland Dreier , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, openib-general@openib.org Subject: Re: [openib-general] [PATCH 5/5] [RFC] Infiniband: connection abstraction Message-ID: <20060118184945.GG6818@esmail.cup.hp.com> References: <43CE8695.9080401@ichips.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <43CE8695.9080401@ichips.intel.com> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 18, 2006 at 10:19:01AM -0800, Sean Hefty wrote: > Roland Dreier wrote: > > > + UCMA_MAX_BACKLOG = 128 > > > >Is there any reason that we might want to make this a tunable? Maybe > >as a module parameter that's writable in sysfs... > > There's no reason not to make this tunable. Yes, there are reasons to NOT make something a tunable: o increases system complexity (admin) o increases the amount of documentation (learning curve) o increases test matrix/cost (devel/support cost) o generally hurts performance (var vs a constant of the same value) Any reason to make something a tunable has to compensate for the above drawbacks. An answer to Roland's question is a reasonable prerequisite if someone wants add a tunable. IB doesn't have the much in /sys/class/infiniband* or module parameters and I think that's a Good Thing. grant