Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757233Ab0GVV17 (ORCPT ); Thu, 22 Jul 2010 17:27:59 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57771 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753250Ab0GVV16 (ORCPT ); Thu, 22 Jul 2010 17:27:58 -0400 Date: Thu, 22 Jul 2010 17:26:34 -0400 From: Vivek Goyal To: Greg KH Cc: Paul Menage , Li Zefan , Lennart Poettering , Kay Sievers , Andrew Morton , KAMEZAWA Hiroyuki , Ben Blum , containers@lists.linux-foundation.org, linux-kernel@vger.kernel.org, "Daniel P. Berrange" , Jan Safranek , Balbir Singh Subject: Re: [PATCH] cgroupfs: create /sys/fs/cgroup to mount cgroupfs on Message-ID: <20100722212634.GC2688@redhat.com> References: <20100722182638.GA12712@kroah.com> <20100722183614.GA5443@suse.de> <20100722193741.GA2688@redhat.com> <20100722211856.GA1297@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20100722211856.GA1297@suse.de> User-Agent: Mutt/1.5.20 (2009-12-10) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2953 Lines: 67 On Thu, Jul 22, 2010 at 02:18:56PM -0700, Greg KH wrote: > On Thu, Jul 22, 2010 at 03:37:41PM -0400, Vivek Goyal wrote: > > On Thu, Jul 22, 2010 at 11:36:15AM -0700, Greg KH wrote: > > > On Thu, Jul 22, 2010 at 11:31:07AM -0700, Paul Menage wrote: > > > > On Thu, Jul 22, 2010 at 11:26 AM, Greg KH wrote: > > > > > We really shouldn't be asking userspace to create new root filesystems. > > > > > So follow along with all of the other in-kernel filesystems, and provide > > > > > a mount point in sysfs. > > > > > > > > > > For cgroupfs, this should be in /sys/fs/cgroup/ ?This change provides > > > > > that mount point when the cgroup filesystem is registered in the kernel. > > > > > > > > But cgroups will typically have multiple mounts, with different > > > > resource controllers/options on each mount. That doesn't really fit in > > > > with this scheme. > > > > > > Really? I see systems mounting it at /cgroups/ in the filesystem today. > > > Where are you expecting it to be mounted at? > > > > > > > Greg, > > > > [CCing few more folks who might be interested in this dicussion ] > > > > We do want to retain facility to mount different controllers at different > > mount points. We were discussing the other day that in libvirt we might > > want to mount block IO controller and network controller separately as > > by default we will not put a new virtual machine in a cgroup of its own > > because of the penatly involved. > > That's fine, I'm not changing that ability at all. We just need a > "default" mount point for "normal" users. > > > For other controllers like cpu, memory etc, libvirt automatically puts > > each new virtual machine in a cgroup of own. So this is one use case > > where we might want to mount different controllers at different mount > > points. > > > > For my testing I now always use /cgroup/ and create directories under it > > /cgroup/blkio /cgroup/cpu etc and mount controllers on respective > > directories. > > Lennart and Kay, is this what systemd is doing? I really don't think we > should be adding a root /cgroup/ mount point to the system for something > like this. > > Maybe /dev/cgroup/ is better to use, as that way users can create > sub-mount points easier. They can't do that in /sys/fs/cgroup/ The only problem with /dev/cgroup seems to be that it seems little unintutive. To me, we have devices under /dev/ dir and cgroups are not devices. I think people have floated similar threads in the past on lkml with various opinions and everybody had their own choices but nothing was conclusive. Polluting / definitely sounds odd but it does not look that bad once we can't find any other good choices. Thanks Vivek -- 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/