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authorSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>2012-05-24 19:46:41 +0530
committerIngo Molnar <mingo@kernel.org>2012-07-24 13:53:18 +0200
commit80d1fa6463d934969b7aebf04107fc133463f0f6 (patch)
tree9e86e50c41016e68df655890c93a3b200c6a3ec0
parentd35be8bab9b0ce44bed4b9453f86ebf64062721e (diff)
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: 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>
-rw-r--r--kernel/cpuset.c36
1 files changed, 27 insertions, 9 deletions
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 746d1eeb5dbe..ba96349aa522 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1990,6 +1990,32 @@ static void remove_tasks_in_empty_cpuset(struct cpuset *cs)
}
/*
+ * 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) &&