[PATCH v3 5/7] cpuset: allow to keep tasks in empty cpusets
Li Zefan
lizefan at huawei.com
Sun Jun 9 09:16:29 UTC 2013
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.
v3:
- do propagation work in one place for both hotplug and unplug
v2:
- drop rcu_read_lock before calling update_task_nodemask() and
update_task_cpumask(), instead of using workqueue.
- add documentation in include/linux/cgroup.h
Signed-off-by: Li Zefan <lizefan at huawei.com>
---
include/linux/cgroup.h | 4 ++
kernel/cpuset.c | 141 ++++++++++++++++++++++++++++++++++++++-----------
2 files changed, 114 insertions(+), 31 deletions(-)
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index d0ad379..53e81a6 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -277,6 +277,10 @@ enum {
*
* - Remount is disallowed.
*
+ * - cpuset: tasks will be kept in empty cpusets when hotplug happens
+ * and take masks of ancestors with non-empty cpus/mems, instead of
+ * being moved to an ancestor.
+ *
* - memcg: use_hierarchy is on by default and the cgroup file for
* the flag is not created.
*
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index aab014f..fd7572f 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -874,6 +874,45 @@ 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;
+ }
+ if (!css_tryget(&cp->css))
+ continue;
+ rcu_read_unlock();
+
+ update_tasks_cpumask(cp, heap);
+
+ rcu_read_lock();
+ css_put(&cp->css);
+ }
+ rcu_read_unlock();
+}
+
/**
* update_cpumask - update the cpus_allowed mask of a cpuset and all tasks in it
* @cs: the cpuset to consider
@@ -925,11 +964,7 @@ 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);
@@ -1097,6 +1132,45 @@ static void update_tasks_nodemask(struct cpuset *cs, struct ptr_heap *heap)
}
/*
+ * 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;
+ }
+ if (!css_tryget(&cp->css))
+ continue;
+ rcu_read_unlock();
+
+ update_tasks_nodemask(cp, heap);
+
+ rcu_read_lock();
+ css_put(&cp->css);
+ }
+ rcu_read_unlock();
+}
+
+/*
* Handle user request to change the 'mems' memory placement
* of a cpuset. Needs to validate the request, update the
* cpusets mems_allowed, and for each task in the cpuset,
@@ -1160,7 +1234,7 @@ 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:
@@ -2048,6 +2122,7 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs)
static cpumask_t off_cpus;
static nodemask_t off_mems;
bool is_empty;
+ bool sane = cgroup_sane_behavior(cs->css.cgroup);
retry:
wait_event(cpuset_attach_wq, cs->attach_in_progress == 0);
@@ -2066,21 +2141,29 @@ retry:
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 sane_behavior flag is set, we need to update tasks' cpumask
+ * for empty cpuset to take on ancestor's cpumask.
+ */
+ if ((sane && cpumask_empty(cs->cpus_allowed)) ||
+ !cpumask_empty(&off_cpus))
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 sane_behavior flag is set, we need to update tasks' nodemask
+ * for empty cpuset to take on ancestor's nodemask.
+ */
+ if ((sane && nodes_empty(cs->mems_allowed)) ||
+ !nodes_empty(off_mems))
update_tasks_nodemask(cs, NULL);
- }
is_empty = cpumask_empty(cs->cpus_allowed) ||
nodes_empty(cs->mems_allowed);
@@ -2088,11 +2171,13 @@ retry:
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);
}
@@ -2114,10 +2199,9 @@ retry:
*/
static void cpuset_hotplug_workfn(struct work_struct *work)
{
- static cpumask_t new_cpus, tmp_cpus;
- static nodemask_t new_mems, tmp_mems;
+ static cpumask_t new_cpus;
+ static nodemask_t new_mems;
bool cpus_updated, mems_updated;
- bool cpus_offlined, mems_offlined;
mutex_lock(&cpuset_mutex);
@@ -2126,12 +2210,7 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
new_mems = node_states[N_MEMORY];
cpus_updated = !cpumask_equal(top_cpuset.cpus_allowed, &new_cpus);
- cpus_offlined = cpumask_andnot(&tmp_cpus, top_cpuset.cpus_allowed,
- &new_cpus);
-
mems_updated = !nodes_equal(top_cpuset.mems_allowed, new_mems);
- nodes_andnot(tmp_mems, top_cpuset.mems_allowed, new_mems);
- mems_offlined = !nodes_empty(tmp_mems);
/* synchronize cpus_allowed to cpu_active_mask */
if (cpus_updated) {
@@ -2151,8 +2230,8 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
mutex_unlock(&cpuset_mutex);
- /* if cpus or mems went down, we need to propagate to descendants */
- if (cpus_offlined || mems_offlined) {
+ /* if cpus or mems changed, we need to propagate to descendants */
+ if (cpus_updated || mems_updated) {
struct cpuset *cs;
struct cgroup *pos_cgrp;
--
1.8.0.2
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