Permalink
Browse files

cpusets, hotplug: Restructure functions that are invoked during hotplug

Separate out the cpuset related handling for CPU/Memory online/offline.
This also helps us exploit the most obvious and basic level of optimization
that any notification mechanism (CPU/Mem online/offline) has to offer us:
"We *know* why we have been invoked. So stop pretending that we are lost,
and do only the necessary amount of processing!".

And while at it, rename scan_for_empty_cpusets() to
scan_cpusets_upon_hotplug(), which is more appropriate considering how
it is restructured.

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/20120524141650.3692.48637.stgit@srivatsabhat.in.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
  • Loading branch information...
Srivatsa S. Bhat Ingo Molnar
Srivatsa S. Bhat authored and Ingo Molnar committed May 24, 2012
1 parent 80d1fa6 commit 7ddf96b02fe8dd441f452deef879040def5f7b34
Showing with 65 additions and 31 deletions.
  1. +2 −2 include/linux/cpuset.h
  2. +61 −27 kernel/cpuset.c
  3. +2 −2 kernel/sched/core.c
View
@@ -20,7 +20,7 @@ extern int number_of_cpusets; /* How many cpusets are defined in system? */
extern int cpuset_init(void);
extern void cpuset_init_smp(void);
-extern void cpuset_update_active_cpus(void);
+extern void cpuset_update_active_cpus(bool cpu_online);
extern void cpuset_cpus_allowed(struct task_struct *p, struct cpumask *mask);
extern void cpuset_cpus_allowed_fallback(struct task_struct *p);
extern nodemask_t cpuset_mems_allowed(struct task_struct *p);
@@ -124,7 +124,7 @@ static inline void set_mems_allowed(nodemask_t nodemask)
static inline int cpuset_init(void) { return 0; }
static inline void cpuset_init_smp(void) {}
-static inline void cpuset_update_active_cpus(void)
+static inline void cpuset_update_active_cpus(bool cpu_online)
{
partition_sched_domains(1, NULL, NULL);
}
View
@@ -147,6 +147,12 @@ typedef enum {
CS_SPREAD_SLAB,
} cpuset_flagbits_t;
+/* the type of hotplug event */
+enum hotplug_event {
+ CPUSET_CPU_OFFLINE,
+ CPUSET_MEM_OFFLINE,
+};
+
/* convenient tests for these bits */
static inline int is_cpu_exclusive(const struct cpuset *cs)
{
@@ -2016,8 +2022,10 @@ static struct cpuset *cpuset_next(struct list_head *queue)
/*
- * Walk the specified cpuset subtree and look for empty cpusets.
- * The tasks of such cpuset must be moved to a parent cpuset.
+ * Walk the specified cpuset subtree upon a hotplug operation (CPU/Memory
+ * online/offline) and update the cpusets accordingly.
+ * For regular CPU/Mem hotplug, look for empty cpusets; the tasks of such
+ * cpuset must be moved to a parent cpuset.
*
* Called with cgroup_mutex held. We take callback_mutex to modify
* cpus_allowed and mems_allowed.
@@ -2030,38 +2038,58 @@ static struct cpuset *cpuset_next(struct list_head *queue)
* that has tasks along with an empty 'mems'. But if we did see such
* a cpuset, we'd handle it just like we do if its 'cpus' was empty.
*/
-static void scan_for_empty_cpusets(struct cpuset *root)
+static void
+scan_cpusets_upon_hotplug(struct cpuset *root, enum hotplug_event event)
{
LIST_HEAD(queue);
- struct cpuset *cp; /* scans cpusets being updated */
+ struct cpuset *cp; /* scans cpusets being updated */
static nodemask_t oldmems; /* protected by cgroup_mutex */
list_add_tail((struct list_head *)&root->stack_list, &queue);
- while ((cp = cpuset_next(&queue)) != NULL) {
+ switch (event) {
+ case CPUSET_CPU_OFFLINE:
+ while ((cp = cpuset_next(&queue)) != NULL) {
+
+ /* Continue past cpusets with all cpus online */
+ if (cpumask_subset(cp->cpus_allowed, cpu_active_mask))
+ continue;
+
+ /* Remove offline cpus from this cpuset. */
+ mutex_lock(&callback_mutex);
+ cpumask_and(cp->cpus_allowed, cp->cpus_allowed,
+ cpu_active_mask);
+ mutex_unlock(&callback_mutex);
+
+ /* Move tasks from the empty cpuset to a parent */
+ if (cpumask_empty(cp->cpus_allowed))
+ remove_tasks_in_empty_cpuset(cp);
+ else
+ update_tasks_cpumask(cp, NULL);
+ }
+ break;
- /* Continue past cpusets with all cpus, mems online */
- if (cpumask_subset(cp->cpus_allowed, cpu_active_mask) &&
- nodes_subset(cp->mems_allowed, node_states[N_HIGH_MEMORY]))
- continue;
+ case CPUSET_MEM_OFFLINE:
+ while ((cp = cpuset_next(&queue)) != NULL) {
- oldmems = cp->mems_allowed;
+ /* Continue past cpusets with all mems online */
+ if (nodes_subset(cp->mems_allowed,
+ node_states[N_HIGH_MEMORY]))
+ continue;
- /* Remove offline cpus and mems from this cpuset. */
- mutex_lock(&callback_mutex);
- cpumask_and(cp->cpus_allowed, cp->cpus_allowed,
- cpu_active_mask);
- nodes_and(cp->mems_allowed, cp->mems_allowed,
+ oldmems = cp->mems_allowed;
+
+ /* Remove offline mems from this cpuset. */
+ mutex_lock(&callback_mutex);
+ nodes_and(cp->mems_allowed, cp->mems_allowed,
node_states[N_HIGH_MEMORY]);
- mutex_unlock(&callback_mutex);
+ mutex_unlock(&callback_mutex);
- /* Move tasks from the empty cpuset to a parent */
- if (cpumask_empty(cp->cpus_allowed) ||
- nodes_empty(cp->mems_allowed))
- remove_tasks_in_empty_cpuset(cp);
- else {
- update_tasks_cpumask(cp, NULL);
- update_tasks_nodemask(cp, &oldmems, NULL);
+ /* Move tasks from the empty cpuset to a parent */
+ if (nodes_empty(cp->mems_allowed))
+ remove_tasks_in_empty_cpuset(cp);
+ else
+ update_tasks_nodemask(cp, &oldmems, NULL);
}
}
}
@@ -2080,8 +2108,11 @@ static void scan_for_empty_cpusets(struct cpuset *root)
*
* Called within get_online_cpus(). Needs to call cgroup_lock()
* before calling generate_sched_domains().
+ *
+ * @cpu_online: Indicates whether this is a CPU online event (true) or
+ * a CPU offline event (false).
*/
-void cpuset_update_active_cpus(void)
+void cpuset_update_active_cpus(bool cpu_online)
{
struct sched_domain_attr *attr;
cpumask_var_t *doms;
@@ -2091,7 +2122,10 @@ void cpuset_update_active_cpus(void)
mutex_lock(&callback_mutex);
cpumask_copy(top_cpuset.cpus_allowed, cpu_active_mask);
mutex_unlock(&callback_mutex);
- scan_for_empty_cpusets(&top_cpuset);
+
+ if (!cpu_online)
+ scan_cpusets_upon_hotplug(&top_cpuset, CPUSET_CPU_OFFLINE);
+
ndoms = generate_sched_domains(&doms, &attr);
cgroup_unlock();
@@ -2122,9 +2156,9 @@ static int cpuset_track_online_nodes(struct notifier_block *self,
case MEM_OFFLINE:
/*
* needn't update top_cpuset.mems_allowed explicitly because
- * scan_for_empty_cpusets() will update it.
+ * scan_cpusets_upon_hotplug() will update it.
*/
- scan_for_empty_cpusets(&top_cpuset);
+ scan_cpusets_upon_hotplug(&top_cpuset, CPUSET_MEM_OFFLINE);
break;
default:
break;
View
@@ -7134,7 +7134,7 @@ static int cpuset_cpu_active(struct notifier_block *nfb, unsigned long action,
case CPU_ONLINE:
case CPU_DOWN_FAILED:
- cpuset_update_active_cpus();
+ cpuset_update_active_cpus(true);
break;
default:
return NOTIFY_DONE;
@@ -7147,7 +7147,7 @@ static int cpuset_cpu_inactive(struct notifier_block *nfb, unsigned long action,
{
switch (action) {
case CPU_DOWN_PREPARE:
- cpuset_update_active_cpus();
+ cpuset_update_active_cpus(false);
break;
case CPU_DOWN_PREPARE_FROZEN:
num_cpus_frozen++;

0 comments on commit 7ddf96b

Please sign in to comment.