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. 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@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
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070b57fcac
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5c5cc62321
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@ -277,6 +277,10 @@ enum {
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*
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* - Remount is disallowed.
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*
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* - cpuset: tasks will be kept in empty cpusets when hotplug happens
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* and take masks of ancestors with non-empty cpus/mems, instead of
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* being moved to an ancestor.
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*
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* - memcg: use_hierarchy is on by default and the cgroup file for
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* the flag is not created.
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*
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143
kernel/cpuset.c
143
kernel/cpuset.c
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@ -874,6 +874,45 @@ static void update_tasks_cpumask(struct cpuset *cs, struct ptr_heap *heap)
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cgroup_scan_tasks(&scan);
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}
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/*
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* update_tasks_cpumask_hier - Update the cpumasks of tasks in the hierarchy.
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* @root_cs: the root cpuset of the hierarchy
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* @update_root: update root cpuset or not?
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* @heap: the heap used by cgroup_scan_tasks()
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*
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* This will update cpumasks of tasks in @root_cs and all other empty cpusets
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* which take on cpumask of @root_cs.
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*
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* Called with cpuset_mutex held
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*/
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static void update_tasks_cpumask_hier(struct cpuset *root_cs,
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bool update_root, struct ptr_heap *heap)
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{
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struct cpuset *cp;
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struct cgroup *pos_cgrp;
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if (update_root)
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update_tasks_cpumask(root_cs, heap);
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rcu_read_lock();
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cpuset_for_each_descendant_pre(cp, pos_cgrp, root_cs) {
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/* skip the whole subtree if @cp have some CPU */
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if (!cpumask_empty(cp->cpus_allowed)) {
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pos_cgrp = cgroup_rightmost_descendant(pos_cgrp);
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continue;
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}
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if (!css_tryget(&cp->css))
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continue;
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rcu_read_unlock();
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update_tasks_cpumask(cp, heap);
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rcu_read_lock();
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css_put(&cp->css);
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}
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rcu_read_unlock();
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}
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/**
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* update_cpumask - update the cpus_allowed mask of a cpuset and all tasks in it
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* @cs: the cpuset to consider
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@ -925,11 +964,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
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cpumask_copy(cs->cpus_allowed, trialcs->cpus_allowed);
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mutex_unlock(&callback_mutex);
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/*
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* Scan tasks in the cpuset, and update the cpumasks of any
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* that need an update.
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*/
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update_tasks_cpumask(cs, &heap);
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update_tasks_cpumask_hier(cs, true, &heap);
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heap_free(&heap);
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@ -1096,6 +1131,45 @@ static void update_tasks_nodemask(struct cpuset *cs, struct ptr_heap *heap)
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cpuset_being_rebound = NULL;
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}
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/*
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* update_tasks_nodemask_hier - Update the nodemasks of tasks in the hierarchy.
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* @cs: the root cpuset of the hierarchy
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* @update_root: update the root cpuset or not?
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* @heap: the heap used by cgroup_scan_tasks()
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*
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* This will update nodemasks of tasks in @root_cs and all other empty cpusets
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* which take on nodemask of @root_cs.
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*
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* Called with cpuset_mutex held
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*/
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static void update_tasks_nodemask_hier(struct cpuset *root_cs,
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bool update_root, struct ptr_heap *heap)
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{
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struct cpuset *cp;
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struct cgroup *pos_cgrp;
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if (update_root)
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update_tasks_nodemask(root_cs, heap);
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rcu_read_lock();
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cpuset_for_each_descendant_pre(cp, pos_cgrp, root_cs) {
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/* skip the whole subtree if @cp have some CPU */
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if (!nodes_empty(cp->mems_allowed)) {
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pos_cgrp = cgroup_rightmost_descendant(pos_cgrp);
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continue;
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}
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if (!css_tryget(&cp->css))
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continue;
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rcu_read_unlock();
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update_tasks_nodemask(cp, heap);
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rcu_read_lock();
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css_put(&cp->css);
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}
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rcu_read_unlock();
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}
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/*
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* Handle user request to change the 'mems' memory placement
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* of a cpuset. Needs to validate the request, update the
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@ -1160,7 +1234,7 @@ static int update_nodemask(struct cpuset *cs, struct cpuset *trialcs,
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cs->mems_allowed = trialcs->mems_allowed;
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mutex_unlock(&callback_mutex);
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update_tasks_nodemask(cs, &heap);
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update_tasks_nodemask_hier(cs, true, &heap);
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heap_free(&heap);
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done:
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@ -2048,6 +2122,7 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs)
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static cpumask_t off_cpus;
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static nodemask_t off_mems;
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bool is_empty;
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bool sane = cgroup_sane_behavior(cs->css.cgroup);
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retry:
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wait_event(cpuset_attach_wq, cs->attach_in_progress == 0);
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@ -2066,21 +2141,29 @@ retry:
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cpumask_andnot(&off_cpus, cs->cpus_allowed, top_cpuset.cpus_allowed);
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nodes_andnot(off_mems, cs->mems_allowed, top_cpuset.mems_allowed);
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/* remove offline cpus from @cs */
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if (!cpumask_empty(&off_cpus)) {
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mutex_lock(&callback_mutex);
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cpumask_andnot(cs->cpus_allowed, cs->cpus_allowed, &off_cpus);
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mutex_unlock(&callback_mutex);
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update_tasks_cpumask(cs, NULL);
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}
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mutex_lock(&callback_mutex);
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cpumask_andnot(cs->cpus_allowed, cs->cpus_allowed, &off_cpus);
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mutex_unlock(&callback_mutex);
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/* remove offline mems from @cs */
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if (!nodes_empty(off_mems)) {
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mutex_lock(&callback_mutex);
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nodes_andnot(cs->mems_allowed, cs->mems_allowed, off_mems);
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mutex_unlock(&callback_mutex);
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/*
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* If sane_behavior flag is set, we need to update tasks' cpumask
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* for empty cpuset to take on ancestor's cpumask.
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*/
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if ((sane && cpumask_empty(cs->cpus_allowed)) ||
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!cpumask_empty(&off_cpus))
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update_tasks_cpumask(cs, NULL);
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mutex_lock(&callback_mutex);
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nodes_andnot(cs->mems_allowed, cs->mems_allowed, off_mems);
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mutex_unlock(&callback_mutex);
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/*
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* If sane_behavior flag is set, we need to update tasks' nodemask
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* for empty cpuset to take on ancestor's nodemask.
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*/
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if ((sane && nodes_empty(cs->mems_allowed)) ||
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!nodes_empty(off_mems))
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update_tasks_nodemask(cs, NULL);
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}
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is_empty = cpumask_empty(cs->cpus_allowed) ||
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nodes_empty(cs->mems_allowed);
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mutex_unlock(&cpuset_mutex);
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/*
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* If @cs became empty, move tasks to the nearest ancestor with
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* execution resources. This is full cgroup operation which will
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* If sane_behavior flag is set, we'll keep tasks in empty cpusets.
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*
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* Otherwise move tasks to the nearest ancestor with execution
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* resources. This is full cgroup operation which will
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* also call back into cpuset. Should be done outside any lock.
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*/
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if (is_empty)
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if (!sane && is_empty)
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remove_tasks_in_empty_cpuset(cs);
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}
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@ -2114,10 +2199,9 @@ retry:
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*/
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static void cpuset_hotplug_workfn(struct work_struct *work)
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{
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static cpumask_t new_cpus, tmp_cpus;
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static nodemask_t new_mems, tmp_mems;
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static cpumask_t new_cpus;
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static nodemask_t new_mems;
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bool cpus_updated, mems_updated;
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bool cpus_offlined, mems_offlined;
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mutex_lock(&cpuset_mutex);
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new_mems = node_states[N_MEMORY];
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cpus_updated = !cpumask_equal(top_cpuset.cpus_allowed, &new_cpus);
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cpus_offlined = cpumask_andnot(&tmp_cpus, top_cpuset.cpus_allowed,
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&new_cpus);
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mems_updated = !nodes_equal(top_cpuset.mems_allowed, new_mems);
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nodes_andnot(tmp_mems, top_cpuset.mems_allowed, new_mems);
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mems_offlined = !nodes_empty(tmp_mems);
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/* synchronize cpus_allowed to cpu_active_mask */
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if (cpus_updated) {
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mutex_unlock(&cpuset_mutex);
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/* if cpus or mems went down, we need to propagate to descendants */
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if (cpus_offlined || mems_offlined) {
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/* if cpus or mems changed, we need to propagate to descendants */
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if (cpus_updated || mems_updated) {
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struct cpuset *cs;
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struct cgroup *pos_cgrp;
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