On Thu, Jun 28, 2012 at 02:55:59PM +0200, Andrea Arcangeli wrote:

This is where the dynamically allocated sched_autonuma structure is
being handled.

The reason for keeping this outside of the task_struct besides not
using too much kernel stack, is to only allocate it on NUMA
hardware. So the not NUMA hardware only pays the memory of a pointer
in the kernel stack (which remains NULL at all times in that case). 

.. snip..

+	if (unlikely(alloc_task_autonuma(tsk, orig, node)))
+		/* free_thread_info() undoes arch_dup_task_struct() too */
+		goto out_thread_info;
 

That looks (without seeing the implementation) and from reading the git
commit, like that on non-NUMA machines it would fail - and end up
stop the creation of a task.

Perhaps a better name for the function: alloc_always_task_autonuma
since the function (at least from the description of this patch) will
always succeed. Perhaps even remove the:
"if unlikely(..)" bit?

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