From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lennart Poettering Subject: Re: cgroup: status-quo and userland efforts Date: Sat, 29 Jun 2013 03:48:16 +0200 Message-ID: <51CE3CE0.9010506@redhat.com> References: <20130625000118.GT1918@mtj.dyndns.org> <20130626212047.GB4536@htj.dyndns.org> <1372311907.5871.78.camel@marge.simpson.net> <20130627180143.GD5599@mtj.dyndns.org> <1372391198.5989.110.camel@marge.simpson.net> <20130628040930.GC2500@htj.dyndns.org> <1372394950.5989.128.camel@marge.simpson.net> <20130628050138.GD2500@htj.dyndns.org> <20130628150513.GD5125@dhcp22.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Tim Hockin Cc: jpoimboe , Mike Galbraith , Containers , Kay Sievers , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , workman-devel , Michal Hocko , "dhaval.giani" , Tejun Heo , Cgroups List-Id: containers.vger.kernel.org On 28.06.2013 20:53, Tim Hockin wrote: > a single-agent, we should make a kick-ass implementation that is > flexible and scalable, and full-featured enough to not require > divergence at the lowest layer of the stack. Then build systemd on > top of that. Let systemd offer more features and policies and > "semantic" APIs. Well, what if systemd is already kick-ass? I mean, if you have a problem with systemd, then that's your own problem, but I really don't think why I should bother? I for sure am not going to make the PID 1 a client of another daemon. That's just wrong. If you have a daemon that is both conceptually the manager of another service and the client of that other service, then that's bad design and you will easily run into deadlocks and such. Just think about it: if you have some external daemon for managing cgroups, and you need cgroups for running external daemons, how are you going to start the external daemon for managing cgroups? Sure, you can hack around this, make that daemon special, and magic, and stuff -- or you can just not do such nonsense. There's no reason to repeat the fuckup that cgroup became in kernelspace a second time, but this time in userspace, with multiple manager daemons all with different and slightly incompatible definitions what a unit to manage actualy is... We want to run fewer, simpler things on our systems, we want to reuse as much of the code as we can. You don't achieve that by running yet another daemon that does worse what systemd can anyway do simpler, easier and better. The least you could grant us is to have a look at the final APIs we will have to offer before you already imply that systemd cannot be a valid implementation of any API people could ever agree on. Lennart From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753396Ab3F2Bsk (ORCPT ); Fri, 28 Jun 2013 21:48:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37319 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752802Ab3F2Bsi (ORCPT ); Fri, 28 Jun 2013 21:48:38 -0400 Message-ID: <51CE3CE0.9010506@redhat.com> Date: Sat, 29 Jun 2013 03:48:16 +0200 From: Lennart Poettering Organization: Red Hat, Inc. User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130612 Thunderbird/17.0.6 MIME-Version: 1.0 To: Tim Hockin CC: Michal Hocko , Tejun Heo , Mike Galbraith , Li Zefan , Containers , Cgroups , bsingharora , "dhaval.giani" , Kay Sievers , jpoimboe , "Daniel P. Berrange" , workman-devel , "linux-kernel@vger.kernel.org" Subject: Re: cgroup: status-quo and userland efforts References: <20130625000118.GT1918@mtj.dyndns.org> <20130626212047.GB4536@htj.dyndns.org> <1372311907.5871.78.camel@marge.simpson.net> <20130627180143.GD5599@mtj.dyndns.org> <1372391198.5989.110.camel@marge.simpson.net> <20130628040930.GC2500@htj.dyndns.org> <1372394950.5989.128.camel@marge.simpson.net> <20130628050138.GD2500@htj.dyndns.org> <20130628150513.GD5125@dhcp22.suse.cz> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 28.06.2013 20:53, Tim Hockin wrote: > a single-agent, we should make a kick-ass implementation that is > flexible and scalable, and full-featured enough to not require > divergence at the lowest layer of the stack. Then build systemd on > top of that. Let systemd offer more features and policies and > "semantic" APIs. Well, what if systemd is already kick-ass? I mean, if you have a problem with systemd, then that's your own problem, but I really don't think why I should bother? I for sure am not going to make the PID 1 a client of another daemon. That's just wrong. If you have a daemon that is both conceptually the manager of another service and the client of that other service, then that's bad design and you will easily run into deadlocks and such. Just think about it: if you have some external daemon for managing cgroups, and you need cgroups for running external daemons, how are you going to start the external daemon for managing cgroups? Sure, you can hack around this, make that daemon special, and magic, and stuff -- or you can just not do such nonsense. There's no reason to repeat the fuckup that cgroup became in kernelspace a second time, but this time in userspace, with multiple manager daemons all with different and slightly incompatible definitions what a unit to manage actualy is... We want to run fewer, simpler things on our systems, we want to reuse as much of the code as we can. You don't achieve that by running yet another daemon that does worse what systemd can anyway do simpler, easier and better. The least you could grant us is to have a look at the final APIs we will have to offer before you already imply that systemd cannot be a valid implementation of any API people could ever agree on. Lennart