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    SubjectRe: [PATCH] cgroupfs: create /sys/fs/cgroup to mount cgroupfs on
    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 <gregkh@suse.de> 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/

    thanks,

    greg k-h
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