Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964877AbVLEXld (ORCPT ); Mon, 5 Dec 2005 18:41:33 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964878AbVLEXld (ORCPT ); Mon, 5 Dec 2005 18:41:33 -0500 Received: from embla.aitel.hist.no ([158.38.50.22]:24535 "HELO embla.aitel.hist.no") by vger.kernel.org with SMTP id S964877AbVLEXlc (ORCPT ); Mon, 5 Dec 2005 18:41:32 -0500 Date: Tue, 6 Dec 2005 00:45:00 +0100 To: Alex Davis Cc: linux-kernel@vger.kernel.org Subject: Re: [2.6 patch] i386: always use 4k stacks Message-ID: <20051205234500.GA19164@aitel.hist.no> References: <20051205214545.41191.qmail@web50212.mail.yahoo.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20051205214545.41191.qmail@web50212.mail.yahoo.com> User-Agent: Mutt/1.5.9i From: Helge Hafting Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1621 Lines: 33 On Mon, Dec 05, 2005 at 01:45:44PM -0800, Alex Davis wrote: > The issues with wireless drivers, as far as I've heard, still haven't been resolved. > > I've read all about the advantages of 4K, but, so far, no one has > really explained the _disadvantes_ to kernel developers of allowing > people to choose their own stack size. > The disadvantage of choice is that the kernel code gets more complicated. 8k stacks are two contigous pages. So fork() have to ask for two contigous pages, and handle cases where 8k is available but not contigous. All that code disappear if the _choice_ is removed. fork() and friends will ask for 4k only - nothing special - and either succeed or go OOM. This was just an example, there are probably more to it. With choice, people can have a fast 4k-stack kernel with all the advantages, or an 8k-stack kernel that survives heavy stack usage. But a developer working on the VM system is slowed down by having to understand and consider both cases when making changes. Someone considering only the 4k case might break the 8k case and vice-versa. I don't really know if we're ready for dropping 8k stack support. But when it happens, VM development will be a bit easier. Get enough such simplifications and it makes a real difference. Collect enough choices & options, and it'll make a difference the other way too. Helge Hafting - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/