From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753128AbaEFSdN (ORCPT ); Tue, 6 May 2014 14:33:13 -0400 Received: from mail-ob0-f178.google.com ([209.85.214.178]:60808 "EHLO mail-ob0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751255AbaEFSdL (ORCPT ); Tue, 6 May 2014 14:33:11 -0400 MIME-Version: 1.0 In-Reply-To: <20140506175547.GE20776@cloud> References: <20140506155703.GA20391@cloud> <20140506.115941.428706504757835279.davem@davemloft.net> <20140506164108.GA20536@cloud> <20140506.131643.994244006906866938.davem@davemloft.net> <20140506175547.GE20776@cloud> Date: Tue, 6 May 2014 11:33:11 -0700 Message-ID: Subject: Re: [PATCH 08/24] net, diet: Make TCP metrics optional From: Cong Wang To: Josh Triplett Cc: David Miller , Andi Kleen , Linux Kernel Network Developers , LKML , tom.zanussi@linux.intel.com, Andi Kleen Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 6, 2014 at 10:55 AM, wrote: > On Tue, May 06, 2014 at 01:16:43PM -0400, David Miller wrote: >> From: josh@joshtriplett.org >> Date: Tue, 6 May 2014 09:41:08 -0700 >> >> > Every KB of RAM costs real money and SoC die area (for eDRAM/eSRAM). >> >> Another poster commented that 16MB of DRAM would be cheaper than >> the 2MB of ram you have on these boards, probably one that fits >> your size profile is available as well. >> >> 2MB is just a rediculous restriction. > > Embedded systems experts disagree with you there; there *are* systems > where the most cost-efficient approach is a few MB (or a few hundred KB) > of non-discrete memory. We're not talking about socketed memory or even > soldered-down memory; we're talking about entire systems that fit on a > small SoC die. The space not used by that extra RAM may well be better > spent on CPU optimizations, or some other integrated component. > > Such boards will be built, and many of them will run Linux, despite your > incredulity. When you're building millions of a board, it's well worth > optimizing software to eliminate components from the bill of materials. So why bothers 3.15+ Linux kernel? Why not use an old kernel e.g. 2.4.x? 2.4.x kernel doesn't have so many new features you want to get rid of here.