From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932796AbXCKDQg (ORCPT ); Sat, 10 Mar 2007 22:16:36 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932805AbXCKDQg (ORCPT ); Sat, 10 Mar 2007 22:16:36 -0500 Received: from smtp.osdl.org ([65.172.181.24]:34896 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932796AbXCKDQe (ORCPT ); Sat, 10 Mar 2007 22:16:34 -0500 Date: Sat, 10 Mar 2007 19:16:14 -0800 From: Andrew Morton To: "Con Kolivas" Cc: mpm@selenic.com, linux-kernel@vger.kernel.org, ck@vds.kolivas.org Subject: Re: RSDL-mm 0.28 Message-Id: <20070310191614.5ac3cf4b.akpm@linux-foundation.org> In-Reply-To: <8cd998d50703101828l71fbec7bi9a819ad7b7fd9828@mail.gmail.com> References: <20070311013506.GD10459@waste.org> <8cd998d50703101828l71fbec7bi9a819ad7b7fd9828@mail.gmail.com> X-Mailer: Sylpheed version 2.2.4 (GTK+ 2.8.19; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > On Sun, 11 Mar 2007 13:28:22 +1100 "Con Kolivas" wrote: > Well... are you advocating we change sched_yield semantics to a > gentler form? >>From a practical POV: our present yield() behaviour is so truly awful that it's basically always a bug to use it. This probably isn't a good thing. So yes, I do think that we should have a rethink and try to come up with behaviour which is more in accord with what application developers expect yield() to do. otoh, a) we should have done this five years ago. Instead, we've spent that time training userspace programmers to not use yield(), so perhaps there's little to be gained in changing it now. b) if we _were_ to change yield(), people would use it more, and their applications would of course suck bigtime when run on earlier 2.6 kernels. Bottom line: we've had a _lot_ of problems with the new yield() semantics. We effectively broke back-compatibility by changing its behaviour a lot, and we can't really turn around and blame application developers for that.