Re: [PATCH 0/4] CPU hotplug, cpusets: Fix CPU online handlingrelated to cpusets

From: Peter Zijlstra
Date: Fri Feb 10 2012 - 10:52:14 EST


On Thu, 2012-02-09 at 16:11 +0100, Ingo Molnar wrote:

> > My understanding of the code is that when a CPU is taken
> > offline, it is removed from all the cpusets and then the
> > scan_for_empty_cpusets() function is run to move tasks from
> > empty cpusets to their parent cpusets.
>
> Why is that done that way? offlining a CPU should be an
> invariant as far as cpusets are concerned.

Can't, tasks need to run someplace. There's two choices, add a still
online cpu to the now empty cpuset or move the tasks to a parent that
still has online cpus.

Both are destructive.



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