Re: [PATCH cgroup/for-3.11 1/3] cgroup: mark "tasks" cgroup file as insane

["Daniel P. Berrange" <berrange-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

On Mon, Jun 03, 2013 at 07:13:02PM -0700, Tejun Heo wrote:
> Some resources controlled by cgroup aren't per-task and cgroup core
> allowing threads of a single thread_group to be in different cgroups
> forced memcg do explicitly find the group leader and use it.  This is
> gonna be nasty when transitioning to unified hierarchy and in general
> we don't want and won't support granularity finer than processes.

With libvirt and KVM we require the ability to put different threads
in different cgroups for the "cpu", "cpuset" & "cpuacct" controllers.
This is to allow us to control schedular tunables / placement for
QEMU vCPU threads, independantly of limits for QEMU I/O threads. So
requiring all threads of a process to be in the same cgroup isn't
sufficiently flexible for our needs.

We don't care about this for the other non-CPU related controllers
though.

Daniel
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