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Date: Fri, 19 Apr 2013 20:29:24 +0800
From: Li Zefan <lizefan@...wei.com>
To: Tejun Heo <tj@...nel.org>
CC: LKML <linux-kernel@...r.kernel.org>,
Cgroups <cgroups@...r.kernel.org>,
Containers <containers@...ts.linux-foundation.org>,
Glauber Costa <glommer@...allels.com>
Subject: [PATCH 09/10] cpuset: allow to keep tasks in empty cpusets
To achieve this:
- We call update_tasks_cpumask/nodemask() for empty cpusets when
hotplug happens, instead of moving tasks out of them.
- When a cpuset's masks are changed by writing cpuset.cpus/mems,
we also update tasks in child cpusets which are empty.
Signed-off-by: Li Zefan <lizefan@...wei.com>
---
kernel/cpuset.c | 171 +++++++++++++++++++++++++++++++++++++++++++++++---------
1 file changed, 146 insertions(+), 25 deletions(-)
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 741e652..95e9394 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -99,6 +99,9 @@ struct cpuset {
*/
nodemask_t old_mems_allowed;
+ /* used in cpuset_update_nodemask_workfn() */
+ struct ptr_heap *heap;
+
struct fmeter fmeter; /* memory_pressure filter */
/*
@@ -114,6 +117,7 @@ struct cpuset {
int relax_domain_level;
struct work_struct hotplug_work;
+ struct work_struct update_nodemask_work;
};
/* Retrieve the cpuset for a cgroup */
@@ -276,6 +280,8 @@ static struct cpuset top_cpuset = {
static DEFINE_MUTEX(cpuset_mutex);
static DEFINE_MUTEX(callback_mutex);
+static struct workqueue_struct *cpuset_update_nodemask_wq;
+
/*
* CPU / memory hotplug is handled asynchronously.
*/
@@ -877,6 +883,39 @@ static void update_tasks_cpumask(struct cpuset *cs, struct ptr_heap *heap)
cgroup_scan_tasks(&scan);
}
+/*
+ * update_tasks_cpumask_hier - Update the cpumasks of tasks in the hierarchy.
+ * @root_cs: the root cpuset of the hierarchy
+ * @update_root: update root cpuset or not?
+ * @heap: the heap used by cgroup_scan_tasks()
+ *
+ * This will update cpumasks of tasks in @root_cs and all other empty cpusets
+ * which take on cpumask of @root_cs.
+ *
+ * Called with cpuset_mutex held
+ */
+static void update_tasks_cpumask_hier(struct cpuset *root_cs,
+ bool update_root, struct ptr_heap *heap)
+{
+ struct cpuset *cp;
+ struct cgroup *pos_cgrp;
+
+ if (update_root)
+ update_tasks_cpumask(root_cs, heap);
+
+ rcu_read_lock();
+ cpuset_for_each_descendant_pre(cp, pos_cgrp, root_cs) {
+ /* skip the whole subtree if @cp have some CPU */
+ if (!cpumask_empty(cp->cpus_allowed)) {
+ pos_cgrp = cgroup_rightmost_descendant(pos_cgrp);
+ continue;
+ }
+
+ update_tasks_cpumask(cp, heap);
+ }
+ rcu_read_unlock();
+}
+
/**
* update_cpumask - update the cpus_allowed mask of a cpuset and all tasks in it
* @cs: the cpuset to consider
@@ -928,11 +967,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
cpumask_copy(cs->cpus_allowed, trialcs->cpus_allowed);
mutex_unlock(&callback_mutex);
- /*
- * Scan tasks in the cpuset, and update the cpumasks of any
- * that need an update.
- */
- update_tasks_cpumask(cs, &heap);
+ update_tasks_cpumask_hier(cs, true, &heap);
heap_free(&heap);
@@ -1099,6 +1134,78 @@ static void update_tasks_nodemask(struct cpuset *cs, struct ptr_heap *heap)
cpuset_being_rebound = NULL;
}
+static void cpuset_update_nodemask_workfn(struct work_struct *work)
+{
+ struct cpuset *cs = container_of(work, struct cpuset,
+ update_nodemask_work);
+
+ update_tasks_nodemask(cs, cs->heap);
+ css_put(&cs->css);
+}
+
+static void schedule_update_tasks_nodemask(struct cpuset *cs,
+ struct ptr_heap *heap)
+{
+ bool queued;
+
+ /* Will be released when the work item finishes executing. */
+ if (!css_tryget(&cs->css))
+ return;
+
+ /*
+ * The caller will flush the workqueue with cpuset_mutex held,
+ * so it's not possible a work item was already queued, and
+ * we're sure cs->heap is valid.
+ */
+ cs->heap = heap;
+ queued = queue_work(cpuset_update_nodemask_wq,
+ &cs->update_nodemask_work);
+ if (queued) {
+ WARN_ON(1);
+ css_put(&cs->css);
+ }
+}
+
+/*
+ * update_tasks_nodemask_hier - Update the nodemasks of tasks in the hierarchy.
+ * @cs: the root cpuset of the hierarchy
+ * @update_root: update the root cpuset or not?
+ * @heap: the heap used by cgroup_scan_tasks()
+ *
+ * This will update nodemasks of tasks in @root_cs and all other empty cpusets
+ * which take on nodemask of @root_cs.
+ *
+ * Called with cpuset_mutex held
+ */
+static void update_tasks_nodemask_hier(struct cpuset *root_cs,
+ bool update_root, struct ptr_heap *heap)
+{
+ struct cpuset *cp;
+ struct cgroup *pos_cgrp;
+
+ if (update_root)
+ update_tasks_nodemask(root_cs, heap);
+
+ rcu_read_lock();
+ cpuset_for_each_descendant_pre(cp, pos_cgrp, root_cs) {
+ /* skip the whole subtree if @cp have some CPU */
+ if (!nodes_empty(cp->mems_allowed)) {
+ pos_cgrp = cgroup_rightmost_descendant(pos_cgrp);
+ continue;
+ }
+
+ schedule_update_tasks_nodemask(cp, heap);
+ }
+ rcu_read_unlock();
+
+ /*
+ * The only reason we use workqueue is update_tasks_nodemask() can't
+ * be called in rcu_read_lock(). Flush the workqueue to make sure
+ * all the updates are done before we return.
+ */
+ flush_workqueue(cpuset_update_nodemask_wq);
+}
+
/*
* Handle user request to change the 'mems' memory placement
* of a cpuset. Needs to validate the request, update the
@@ -1163,7 +1270,7 @@ static int update_nodemask(struct cpuset *cs, struct cpuset *trialcs,
cs->mems_allowed = trialcs->mems_allowed;
mutex_unlock(&callback_mutex);
- update_tasks_nodemask(cs, &heap);
+ update_tasks_nodemask_hier(cs, true, &heap);
heap_free(&heap);
done:
@@ -1888,6 +1995,7 @@ static struct cgroup_subsys_state *cpuset_css_alloc(struct cgroup *cont)
nodes_clear(cs->mems_allowed);
fmeter_init(&cs->fmeter);
INIT_WORK(&cs->hotplug_work, cpuset_propagate_hotplug_workfn);
+ INIT_WORK(&cs->update_nodemask_work, cpuset_update_nodemask_workfn);
cs->relax_domain_level = -1;
return &cs->css;
@@ -2063,31 +2171,36 @@ static void cpuset_propagate_hotplug_workfn(struct work_struct *work)
static nodemask_t off_mems;
struct cpuset *cs = container_of(work, struct cpuset, hotplug_work);
bool is_empty;
+ bool sane = cgroup_sane_behavior(cs->css.cgroup);
mutex_lock(&cpuset_mutex);
cpumask_andnot(&off_cpus, cs->cpus_allowed, top_cpuset.cpus_allowed);
nodes_andnot(off_mems, cs->mems_allowed, top_cpuset.mems_allowed);
- /* remove offline cpus from @cs */
- if (!cpumask_empty(&off_cpus)) {
- mutex_lock(&callback_mutex);
- cpumask_andnot(cs->cpus_allowed, cs->cpus_allowed, &off_cpus);
- mutex_unlock(&callback_mutex);
+ mutex_lock(&callback_mutex);
+ cpumask_andnot(cs->cpus_allowed, cs->cpus_allowed, &off_cpus);
+ mutex_unlock(&callback_mutex);
- if (!cpumask_empty(cs->cpus_allowed))
- update_tasks_cpumask(cs, NULL);
- }
+ /*
+ * If sane_behavior flag is set, we need to update tasks' cpumask
+ * for empy cpuset to take on ancestor's cpumask
+ */
+ if ((sane && cpumask_empty(cs->cpus_allowed)) ||
+ (!cpumask_empty(&off_cpus) && !cpumask_empty(cs->cpus_allowed)))
+ update_tasks_cpumask(cs, NULL);
- /* remove offline mems from @cs */
- if (!nodes_empty(off_mems)) {
- mutex_lock(&callback_mutex);
- nodes_andnot(cs->mems_allowed, cs->mems_allowed, off_mems);
- mutex_unlock(&callback_mutex);
+ mutex_lock(&callback_mutex);
+ nodes_andnot(cs->mems_allowed, cs->mems_allowed, off_mems);
+ mutex_unlock(&callback_mutex);
- if (!nodes_empty(cs->mems_allowed))
- update_tasks_nodemask(cs, NULL);
- }
+ /*
+ * If sane_behavior flag is set, we need to update tasks' nodemask
+ * for empy cpuset to take on ancestor's nodemask
+ */
+ if ((sane && nodes_empty(cs->mems_allowed)) ||
+ (!nodes_empty(off_mems) && !nodes_empty(cs->mems_allowed)))
+ update_tasks_nodemask(cs, NULL);
is_empty = cpumask_empty(cs->cpus_allowed) ||
nodes_empty(cs->mems_allowed);
@@ -2095,11 +2208,13 @@ static void cpuset_propagate_hotplug_workfn(struct work_struct *work)
mutex_unlock(&cpuset_mutex);
/*
- * If @cs became empty, move tasks to the nearest ancestor with
- * execution resources. This is full cgroup operation which will
+ * If sane_behavior flag is set, we'll keep tasks in empty cpusets.
+ *
+ * Otherwise move tasks to the nearest ancestor with execution
+ * resources. This is full cgroup operation which will
* also call back into cpuset. Should be done outside any lock.
*/
- if (is_empty)
+ if (!sane && is_empty)
remove_tasks_in_empty_cpuset(cs);
/* the following may free @cs, should be the last operation */
@@ -2174,6 +2289,7 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
cpumask_copy(top_cpuset.cpus_allowed, &new_cpus);
mutex_unlock(&callback_mutex);
/* we don't mess with cpumasks of tasks in top_cpuset */
+ update_tasks_cpumask_hier(&top_cpuset, false, NULL);
}
/* synchronize mems_allowed to N_MEMORY */
@@ -2182,6 +2298,7 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
top_cpuset.mems_allowed = new_mems;
mutex_unlock(&callback_mutex);
update_tasks_nodemask(&top_cpuset, NULL);
+ update_tasks_nodemask_hier(&top_cpuset, false, NULL);
}
/* if cpus or mems went down, we need to propagate to descendants */
@@ -2261,6 +2378,10 @@ void __init cpuset_init_smp(void)
cpuset_propagate_hotplug_wq =
alloc_ordered_workqueue("cpuset_hotplug", 0);
BUG_ON(!cpuset_propagate_hotplug_wq);
+
+ cpuset_update_nodemask_wq =
+ create_workqueue("cpuset_update_nodemask");
+ BUG_ON(!cpuset_update_nodemask_wq);
}
/**
--
1.8.0.2
--
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