From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alessandro Rubini Subject: Re: [PATCH] stmmac: reduce queue lengths if MTU is very large Date: Tue, 20 Dec 2011 08:30:50 +0100 Message-ID: <20111220073050.GA2817@mail.gnudd.com> References: <20111219.163337.1185514300243434827.davem@davemloft.net> <1324273530-18499-1-git-send-email-peppe.cavallaro@st.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: peppe.cavallaro@st.com, netdev@vger.kernel.org, giancarlo.asnaghi@st.com To: davem@davemloft.net Return-path: Received: from mail2.gnudd.com ([213.203.150.91]:61339 "EHLO mail.gnudd.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753036Ab1LTHbD (ORCPT ); Tue, 20 Dec 2011 02:31:03 -0500 Content-Disposition: inline In-Reply-To: <20111219.163337.1185514300243434827.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: > This change doesn't make sense. I disagree, but you are the boss here, so I accept that. > I'm not applying this, it just points out that the amount of reserved > space in your SWIOMMU setup might be insufficient for this situation > rather than something that should be tweaked in this driver. Allocation of the queues is based on a parameter. If the parameter was a size, instead of a lenght, all would be fine, wouldn't it? If you agree, then this patch is turning the lenght into a size, in a way. Now, how could we deal with the fact that the size explodes if the MTU is increased? I don't want to reserve and waste 16MB of RAM for a single device: the device won't even use them for non-jumbo setups. I can use the parameter to shorten the queue in all cases, but this is not good either. What's your suggestion? thanks /alessandro