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Commit 80d1fa64 authored by Srivatsa S. Bhat's avatar Srivatsa S. Bhat Committed by Ingo Molnar
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cpusets, hotplug: Implement cpuset tree traversal in a helper function 



At present, the functions that deal with cpusets during CPU/Mem hotplug
are quite messy, since a lot of the functionality is mixed up without clear
separation. And this takes a toll on optimization as well. For example,
the function cpuset_update_active_cpus() is called on both CPU offline and CPU
online events; and it invokes scan_for_empty_cpusets(), which makes sense
only for CPU offline events. And hence, the current code ends up unnecessarily
traversing the cpuset tree during CPU online also.

As a first step towards cleaning up those functions, encapsulate the cpuset
tree traversal in a helper function, so as to facilitate upcoming changes.

Signed-off-by: default avatarSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20120524141635.3692.893.stgit@srivatsabhat.in.ibm.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent d35be8ba

kernel/cpuset.c

+27 −9
Original line number Diff line number Diff line
@@ -1989,6 +1989,32 @@ static void remove_tasks_in_empty_cpuset(struct cpuset *cs) 
	move_member_tasks_to_cpuset(cs, parent);

}



/*

 * Helper function to traverse cpusets.

 * It can be used to walk the cpuset tree from top to bottom, completing

 * one layer before dropping down to the next (thus always processing a

 * node before any of its children).

 */

static struct cpuset *cpuset_next(struct list_head *queue)

{

	struct cpuset *cp;

	struct cpuset *child;	/* scans child cpusets of cp */

	struct cgroup *cont;



	if (list_empty(queue))

		return NULL;



	cp = list_first_entry(queue, struct cpuset, stack_list);

	list_del(queue->next);

	list_for_each_entry(cont, &cp->css.cgroup->children, sibling) {

		child = cgroup_cs(cont);

		list_add_tail(&child->stack_list, queue);

	}



	return cp;

}





/*

 * Walk the specified cpuset subtree and look for empty cpusets.

 * The tasks of such cpuset must be moved to a parent cpuset.
@@ -2008,19 +2034,11 @@ static void scan_for_empty_cpusets(struct cpuset *root) 
{

	LIST_HEAD(queue);

	struct cpuset *cp;	/* scans cpusets being updated */

	struct cpuset *child;	/* scans child cpusets of cp */

	struct cgroup *cont;

	static nodemask_t oldmems;	/* protected by cgroup_mutex */



	list_add_tail((struct list_head *)&root->stack_list, &queue);



	while (!list_empty(&queue)) {

		cp = list_first_entry(&queue, struct cpuset, stack_list);

		list_del(queue.next);

		list_for_each_entry(cont, &cp->css.cgroup->children, sibling) {

			child = cgroup_cs(cont);

			list_add_tail(&child->stack_list, &queue);

		}

	while ((cp = cpuset_next(&queue)) != NULL) {



		/* Continue past cpusets with all cpus, mems online */

		if (cpumask_subset(cp->cpus_allowed, cpu_active_mask) &&