Currently some cpuset behaviors are not friendly when cpuset is co-mounted
with other cgroup controllers.
Now with this patchset if cpuset is mounted with sane_behavior option,
it behaves differently:
- 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.
- A task can be moved into an empty cpuset, and again it takes masks of
ancestors, so the user can drop a task into a newly created cgroup without
having to do anything for it.
As tasks can reside in empy cpusets, here're some rules:
- They can be moved to another cpuset, regardless it's empty or not.
- Though it takes masks from ancestors, it takes other configs from the
empty cpuset.
- If the ancestors' masks are changed, those tasks will also be updated
to take new masks.
v2: add documentation in include/linux/cgroup.h
Signed-off-by: Li Zefan <lizefan@xxxxxxxxxx>
---
include/linux/cgroup.h | 3 +++
kernel/cpuset.c | 9 +++++++--
2 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 53e81a6..74e8b8e 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -281,6 +281,9 @@ enum {
* and take masks of ancestors with non-empty cpus/mems, instead of
* being moved to an ancestor.
*
+ * - cpuset: a task can be moved into an empty cpuset, and again it
+ * takes masks of ancestors.
+ *
* - 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 fd7572f..d1d6782 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -479,7 +479,7 @@ static int validate_change(const struct cpuset *cur, const struct cpuset *trial)
*/
ret = -ENOSPC;
if ((cgroup_task_count(cur->css.cgroup) || cur->attach_in_progress) &&
- (cpumask_empty(trial->cpus_allowed) ||
+ (cpumask_empty(trial->cpus_allowed) &&
nodes_empty(trial->mems_allowed)))
goto out;
@@ -1466,8 +1466,13 @@ static int cpuset_can_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
mutex_lock(&cpuset_mutex);
+ /*
+ * We allow to move tasks into an empty cpuset if sane_behavior
+ * flag is set.
+ */
ret = -ENOSPC;
- if (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed))
+ if (!cgroup_sane_behavior(cgrp) &&
+ (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed)))
goto out_unlock;
cgroup_taskset_for_each(task, cgrp, tset) {
--
1.8.0.2
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