From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTP id A4C7BAC5 for ; Tue, 10 Jun 2014 20:12:42 +0000 (UTC) Received: from userp1040.oracle.com (userp1040.oracle.com [156.151.31.81]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 2AA8020321 for ; Tue, 10 Jun 2014 20:12:42 +0000 (UTC) Date: Tue, 10 Jun 2014 16:12:36 -0400 From: Konrad Rzeszutek Wilk To: ksummit-discuss@lists.linuxfoundation.org Message-ID: <20140610201236.GA21729@laptop.dumpdata.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Cc: boris.ostrovsky@oracle.com, david.vrabel@citrix.com Subject: [Ksummit-discuss] Topic: Removal of code that is still in use by users but there is a better code. List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hey, I would want to propose a topic on removing code in Linux that users are using - but they are doing it less and less and it mostly is tied in with older hardware. Specifically how to do this transition properly - and if we want to define some checklist /policy to do it via. Specifically in the Xen virtualization world there is in pipeline code that is going to obsolete some of the existing pvops code - and also make lguest obsolete. It makes the Linux kernel run faster, less code to deal with, makes x86 folks happy, and requires newer hardware. This is known as PVH (ParaVirtualization Hardware). So, from one hand - with newer hardware - we can remove some of the code. On the other hand - with older hardware (pre EPT/NPT capable) or low-powered ones - we would making their life difficult and slower (as now the hypervisor has to do the emulation, probably has some bugs, code bitrotten, etc). In essence it boils down to removing code in X years that users do use. There is a nice migration path, but I am sure the moment we rip out the code folks will come out of the woodwork, chase us down, and hit us with clubs. I do enjoy hiking and don't want to have to look behind my back as I am hiking. What I want to propose is a topic to discuss what is the right way to do this? I presume other platforms have had similar issues in the past (or will be) and what is the best way of doing this. Are there any policies in place? P.S. I say in pipeline because it is still experimental, the ABI hasn't been bolted down, and we have tons of outstanding bugs before we let enterprise customers take a stab at it, etc. P.S.S. Peter (hpa) is going to hate that I put 'X' instead of the '5' number. We figured that in 5 years since we get this stable we can start the count-down timer - but the 'getting' stable seems to take longer than I am happy with (#@)@#$ bugs). Hence, X = stable + 5. If there are any