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SubjectRe: [PATCH 1/1] hotplug cpu: migrate a task within its cpuset

* Cliff Wickman <cpw@sgi.com> wrote:

> With this patch, migrate the task to:
> 1) to any cpu on the same node as the disabled cpu, which is both online
> and among that task's cpus_allowed
> 2) to any online cpu within the task's cpuset
> 3) to any cpu which is both online and among that task's cpus_allowed
>
> Diffed against 2.6.21-rc3 (Andrew's current top of tree)

looks good to me.

Acked-by: Ingo Molnar <mingo@elte.hu>

> + /* try to stay on the same cpuset */
> + if (dest_cpu == NR_CPUS) {
> + p->cpus_allowed = cpuset_cpus_allowed(p);
> + dest_cpu = any_online_cpu(p->cpus_allowed);
> + }

what's the practical effect of this - when moving the last CPU offline
from a node you got jobs migrated to really alien nodes? Thus i think we
should queue this up for v2.6.21 too, correct? It's a NOP on systems
that do not set up cpusets, so it's low-risk.

btw., unrelated to your patch, there's this bit right after the code
above:

/* No more Mr. Nice Guy. */
if (dest_cpu == NR_CPUS) {
rq = task_rq_lock(p, &flags);
cpus_setall(p->cpus_allowed);
dest_cpu = any_online_cpu(p->cpus_allowed);
out of consistency, shouldnt the cpus_setall() rather be:

p->cpus_allowed = cpu_possible_map;

? It shouldnt make any real difference but it looks more consistent.

Ingo
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