On Thu, Jan 31, 2008 at 06:39:56PM -0800, Paul Menage wrote: > On Jan 30, 2008 6:40 PM, Srivatsa Vaddagiri <[EMAIL PROTECTED]> wrote: > > > > Here are some questions that arise in this picture: > > > > 1. What is the relationship of the task-group in A/tasks with the > > task-group in A/a1/tasks? In otherwords do they form siblings > > of the same parent A? > > I'd argue the same as Balbir - tasks in A/tasks are are children of A > and are siblings of a1, a2, etc. > > > > > 2. Somewhat related to the above question, how much resource should the > > task-group A/a1/tasks get in relation to A/tasks? Is it 1/2 of parent > > A's share or 1/(1 + N) of parent A's share (where N = number of tasks > > in A/tasks)? > > Each process in A should have a scheduler weight that's derived from > its static_prio field. Similarly each subgroup of A will have a > scheduler weight that's determined by its cpu.shares value. So the cpu > share of any child (be it a task or a subgroup) would be equal to its > own weight divided by the sum of weights of all children. > > So yes, if a task in A forks lots of children, those children could > end up getting a disproportionate amount of the CPU compared to tasks > in A/a1 - but that's the same as the situation without cgroups. If you > want to control cpu usage between different sets of processes in A, > they should be in sibling cgroups, not directly in A. > > Is there a restriction in CFS that stops a given group from > simultaneously holding tasks and sub-groups? If so, couldn't we change > CFS to make it possible rather than enforcing awkward restructions on > cgroups? > > If we really can't change CFS in that way, then an alternative would > be similar to Peter's suggestion - make cpu_cgroup_can_attach() fail > if the cgroup has children, and make cpu_cgroup_create() fail if the > cgroup has any tasks - that way you limit the restriction to just the > hierarchy that has CFS attached to it, rather than generically for all > cgroups > > BTW, I noticed this code in cpu_cgroup_create(): > > /* we support only 1-level deep hierarchical scheduler atm */ > if (cgrp->parent->parent) > return ERR_PTR(-EINVAL); > > Is anyone working on allowing more levels? >
Yes, I am looking at it. > Paul -- regards, Dhaval -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
