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Commit 7ddf96b0 authored by Srivatsa S. Bhat's avatar Srivatsa S. Bhat Committed by Ingo Molnar
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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: 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/20120524141650.3692.48637.stgit@srivatsabhat.in.ibm.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 80d1fa64

include/linux/cpuset.h

+2 −2
Original line number Diff line number Diff line
@@ -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);

}

kernel/cpuset.c

+61 −27
Original line number Diff line number Diff line
@@ -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.
@@ -2030,7 +2038,8 @@ 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 */
@@ -2038,29 +2047,48 @@ static void scan_for_empty_cpusets(struct cpuset *root) 


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



	switch (event) {

	case CPUSET_CPU_OFFLINE:

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



		/* 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 past cpusets with all cpus online */

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

				continue;



		oldmems = cp->mems_allowed;



		/* Remove offline cpus and mems from this cpuset. */

			/* 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;



	case CPUSET_MEM_OFFLINE:

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



			/* Continue past cpusets with all mems online */

			if (nodes_subset(cp->mems_allowed,

					node_states[N_HIGH_MEMORY]))

				continue;



			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);



			/* Move tasks from the empty cpuset to a parent */

		if (cpumask_empty(cp->cpus_allowed) ||

		     nodes_empty(cp->mems_allowed))

			if (nodes_empty(cp->mems_allowed))

				remove_tasks_in_empty_cpuset(cp);

		else {

			update_tasks_cpumask(cp, NULL);

			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;

kernel/sched/core.c

+2 −2
Original line number Diff line number Diff line
@@ -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++;