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SubjectRe: [ckrm-tech] [RFC] Resource Management - Infrastructure choices
On Wed, 1 Nov 2006, Srivatsa Vaddagiri wrote:

> This would forces all tasks in container A to belong to the same mem/io ctlr
> groups. What if that is not desired? How would we achieve something like
> this:
>
> tasks (m) should belong to mem ctlr group D,
> tasks (n, o) should belong to mem ctlr group E
> tasks (m, n, o) should belong to i/o ctlr group G
>

With the example you would need to place task m in one container called
A_m and tasks n and o in another container called A_n,o. Then join A_m to
D, A_n,o to E, and both to G.

I agree that this doesn't appear to be very easy to setup by the sysadmin
or any automated means. But in terms of the kernel, each of these tasks
would have a pointer back to its container and that container would point
to its assigned resource controller. So it's still a double dereference
to access the controller from any task_struct.

So if we proposed a hierarchy of containers, we could have the following:

----------A----------
| | |
-----B----- m -----C------
| | |
n -----D----- o
| |
p q
So instead we make the requirement that only one container can be attached
to any given controller. So if container A is attached to a disk I/O
controller, for example, then it includes all processes. If D is attached
to it instead, only p and q are affected by its constraints.

This would be possible by adding a field to the struct container that
would point to its parent cpu, net, mem, etc. container or NULL if it is
itself.

The difference:

Single-level container hierarchy

struct task_struct {
...
struct container *my_container;
}
struct container {
...
struct controller *my_cpu_controller;
struct controller *my_mem_controller;
}
Multi-level container hierarchy

struct task_struct {
...
struct container *my_container;
}
struct container {
...
/* Root containers, NULL if itself */
struct container *my_cpu_root_container;
struct container *my_mem_root_container;
/* Controllers, NULL if has parent */
struct controller *my_cpu_controller;
struct controller *my_mem_controller;
}
This eliminates the need to put a pointer to each resource controller
within each task_struct.

> (this example breaks the required condition/assumption that a task belong to
> exactly only one process container).
>

Yes, and that was the requirement that the above example was based upon.

David
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