From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751961AbZCPEfU (ORCPT ); Mon, 16 Mar 2009 00:35:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751111AbZCPEfI (ORCPT ); Mon, 16 Mar 2009 00:35:08 -0400 Received: from kroah.org ([198.145.64.141]:59945 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750818AbZCPEfH (ORCPT ); Mon, 16 Mar 2009 00:35:07 -0400 Date: Sun, 15 Mar 2009 21:33:59 -0700 From: Greg KH To: Rory Filer Cc: Ralf Nyren , Stephen Clark , "linux-kernel@vger.kernel.org" , Kevin Lloyd Subject: Re: Sierra Wireless (MC8780) HSDPA speed issue Message-ID: <20090316043359.GA24632@kroah.com> References: <20090314040322.GB3417@kroah.com> <20090314203256.GA7487@kroah.com> <49BC5A90.7070004@earthlink.net> <8F90F944E50427428C60E12A34A309D21C401BAA8D@carmd-exchmb01.sierrawireless.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8F90F944E50427428C60E12A34A309D21C401BAA8D@carmd-exchmb01.sierrawireless.local> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Mar 15, 2009 at 03:30:54PM -0700, Rory Filer wrote: > Hi Ralf > > Using the driver we sent you on a call-box (i.e. with a "perfect" > simulated network connection) on Ubuntu 8.04 we were seeing ~4 Mbps on > the downlink. So I would rule out any problem with the driver and > conclude it must be something in either PPP/Linux or in the modem. In > order to rule out the modem, I've got a question into one of our UMTS > engineers and will send you a reply when we get the answer. > > We did play around a little with 2.4 kernels of Linux and discovered > there is a buffer in PPP_ASYNC.C which, when its size is increased, > doubled the throughput. If you are savvy enough with Linux, you might > want to try playing with that. We stopped short of any thorough > testing of changing this array size, but were pleased with the result. > If I recall properly, the size of this array is (was, in 2.4) 256 > bytes. Doubling it gave an immediate improvement. We were guessing > that the small size of this buffer was fine in the "old days" when > modems peaked at ~56 kbps. Even 8 years ago that was the fastest you > could go with a GPRS product, now our new HSPA+ products yields 21 > Mbps on Telstra's network! Quite a difference. Ah, the OBUFSIZE #define in drivers/net/ppp_async.c? Anyone care to bump this size up and see if that helps out? thanks, greg k-h