On Wed, 20.07.11 16:42, Vivek Goyal (vgoyal(a)redhat.com) wrote:
On Wed, Jul 20, 2011 at 10:28:32PM +0200, Lennart Poettering wrote:
[..]
>
> > Right now, the gui assumes that the various hierarchies are mounted
separately,
> > but that the cpu and cpuacct are co-mounted. Its my understanding that this
> > is consistent with how systemd is doing things. So that's great.
>
> In F15 we mount all controllers enabled in the kernel separately. In F16
> we'll optionally mount some of them together, and we'll probably ship a
> default of mounting cpu and cpuacct together if they are both enabled.
Last time we talked about possibility of co-mounting memory and IO at some
point of time and you said it is a bad idea from applications programming
point of view. Has that changed now?
Well, no, but yes.
After discussing this Dhaval the scheme we came up with is to add
symlinks to /sys/fs/cgroup/ so that even when some controllers are
mounted together they are still available at the the separate
directories. Example, if we mount cpu+cpuacct together things will look
like this:
/sys/fs/cgroup/cpu+cpuacct is the joint mount point.
/sys/fs/cgroup/cpu → /sys/fs/cgroup/cpu+cpuacct is a symlink.
/sys/fs/cgroup/cpuacct → /sys/fs/cgroup/cpu+cpuacct is a symlink.
That way to most applications it will be very easy to support this: they
can simply assume that the controller "foobar" is available under
/sys/fs/cgroup/foobar, and that's it.
Lennart
--
Lennart Poettering - Red Hat, Inc.