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cpusets, hotplug: Implement cpuset tree traversal in a helper function

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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: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Peter 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Srivatsa S. Bhat 2012-05-24 19:46:41 +05:30 committed by Ingo Molnar
parent d35be8bab9
commit 80d1fa6463
1 changed files with 27 additions and 9 deletions
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36
kernel/cpuset.c
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@ -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) &&