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cpusets, hotplug: Restructure functions that are invoked during hotplug

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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>
This commit is contained in:
Srivatsa S. Bhat 2012-05-24 19:46:55 +05:30 committed by Ingo Molnar
parent 80d1fa6463
commit 7ddf96b02f
3 changed files with 65 additions and 31 deletions
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4
include/linux/cpuset.h
View File

@ -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);
}

88
kernel/cpuset.c
View File

@ -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, mems online */
if (cpumask_subset(cp->cpus_allowed, cpu_active_mask) &&
nodes_subset(cp->mems_allowed, node_states[N_HIGH_MEMORY]))
continue;
/* Continue past cpusets with all cpus online */
if (cpumask_subset(cp->cpus_allowed, cpu_active_mask))
continue;
oldmems = cp->mems_allowed;
/* 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);
/* 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,
/* 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);
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;

4
kernel/sched/core.c
View File

@ -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++;