On Wed 28-11-12 14:27:00, Tejun Heo wrote: > Implement cpuset_for_each_descendant_pre() and replace the > cpuset-specific tree walking using cpuset->stack_list with it. > > Signed-off-by: Tejun Heo <[email protected]>
Reviewed-by: Michal Hocko <[email protected]> > --- > kernel/cpuset.c | 123 > ++++++++++++++++++++++---------------------------------- > 1 file changed, 48 insertions(+), 75 deletions(-) > > diff --git a/kernel/cpuset.c b/kernel/cpuset.c > index 2ee0e03..3a01730 100644 > --- a/kernel/cpuset.c > +++ b/kernel/cpuset.c > @@ -103,9 +103,6 @@ struct cpuset { > /* for custom sched domain */ > int relax_domain_level; > > - /* used for walking a cpuset hierarchy */ > - struct list_head stack_list; > - > struct work_struct hotplug_work; > }; > > @@ -207,6 +204,20 @@ static struct cpuset top_cpuset = { > cgroup_for_each_child((pos_cgrp), (parent_cs)->css.cgroup) \ > if (is_cpuset_online(((child_cs) = cgroup_cs((pos_cgrp))))) > > +/** > + * cpuset_for_each_descendant_pre - pre-order walk of a cpuset's descendants > + * @des_cs: loop cursor pointing to the current descendant > + * @pos_cgrp: used for iteration > + * @root_cs: target cpuset to walk ancestor of > + * > + * Walk @des_cs through the online descendants of @root_cs. Must be used > + * with RCU read locked. The caller may modify @pos_cgrp by calling > + * cgroup_rightmost_descendant() to skip subtree. > + */ > +#define cpuset_for_each_descendant_pre(des_cs, pos_cgrp, root_cs) \ > + cgroup_for_each_descendant_pre((pos_cgrp), (root_cs)->css.cgroup) \ > + if (is_cpuset_online(((des_cs) = cgroup_cs((pos_cgrp))))) > + > /* > * There are two global mutexes guarding cpuset structures - cpuset_mutex > * and callback_mutex. The latter may nest inside the former. We also > @@ -507,31 +518,24 @@ update_domain_attr(struct sched_domain_attr *dattr, > struct cpuset *c) > return; > } > > -static void > -update_domain_attr_tree(struct sched_domain_attr *dattr, struct cpuset *c) > +static void update_domain_attr_tree(struct sched_domain_attr *dattr, > + struct cpuset *root_cs) > { > - LIST_HEAD(q); > - > - list_add(&c->stack_list, &q); > - while (!list_empty(&q)) { > - struct cpuset *cp; > - struct cgroup *cont; > - struct cpuset *child; > - > - cp = list_first_entry(&q, struct cpuset, stack_list); > - list_del(q.next); > + struct cpuset *cp; > + struct cgroup *pos_cgrp; > > - if (cpumask_empty(cp->cpus_allowed)) > + rcu_read_lock(); > + cpuset_for_each_descendant_pre(cp, pos_cgrp, root_cs) { > + /* skip the whole subtree if @cp doesn't have any CPU */ > + if (cpumask_empty(cp->cpus_allowed)) { > + pos_cgrp = cgroup_rightmost_descendant(pos_cgrp); > continue; > + } > > if (is_sched_load_balance(cp)) > update_domain_attr(dattr, cp); > - > - rcu_read_lock(); > - cpuset_for_each_child(child, cont, cp) > - list_add_tail(&child->stack_list, &q); > - rcu_read_unlock(); > } > + rcu_read_unlock(); > } > > /* > @@ -591,7 +595,6 @@ update_domain_attr_tree(struct sched_domain_attr *dattr, > struct cpuset *c) > static int generate_sched_domains(cpumask_var_t **domains, > struct sched_domain_attr **attributes) > { > - LIST_HEAD(q); /* queue of cpusets to be scanned */ > struct cpuset *cp; /* scans q */ > struct cpuset **csa; /* array of all cpuset ptrs */ > int csn; /* how many cpuset ptrs in csa so far */ > @@ -600,6 +603,7 @@ static int generate_sched_domains(cpumask_var_t **domains, > struct sched_domain_attr *dattr; /* attributes for custom domains */ > int ndoms = 0; /* number of sched domains in result */ > int nslot; /* next empty doms[] struct cpumask slot */ > + struct cgroup *pos_cgrp; > > doms = NULL; > dattr = NULL; > @@ -627,33 +631,27 @@ static int generate_sched_domains(cpumask_var_t > **domains, > goto done; > csn = 0; > > - list_add(&top_cpuset.stack_list, &q); > - while (!list_empty(&q)) { > - struct cgroup *cont; > - struct cpuset *child; /* scans child cpusets of cp */ > - > - cp = list_first_entry(&q, struct cpuset, stack_list); > - list_del(q.next); > - > - if (cpumask_empty(cp->cpus_allowed)) > - continue; > - > + rcu_read_lock(); > + cpuset_for_each_descendant_pre(cp, pos_cgrp, &top_cpuset) { > /* > - * All child cpusets contain a subset of the parent's cpus, so > - * just skip them, and then we call update_domain_attr_tree() > - * to calc relax_domain_level of the corresponding sched > - * domain. > + * Continue traversing beyond @cp iff @cp has some CPUs and > + * isn't load balancing. The former is obvious. The > + * latter: All child cpusets contain a subset of the > + * parent's cpus, so just skip them, and then we call > + * update_domain_attr_tree() to calc relax_domain_level of > + * the corresponding sched domain. > */ > - if (is_sched_load_balance(cp)) { > - csa[csn++] = cp; > + if (!cpumask_empty(cp->cpus_allowed) && > + !is_sched_load_balance(cp)) > continue; > - } > > - rcu_read_lock(); > - cpuset_for_each_child(child, cont, cp) > - list_add_tail(&child->stack_list, &q); > - rcu_read_unlock(); > - } > + if (is_sched_load_balance(cp)) > + csa[csn++] = cp; > + > + /* skip @cp's subtree */ > + pos_cgrp = cgroup_rightmost_descendant(pos_cgrp); > + } > + rcu_read_unlock(); > > for (i = 0; i < csn; i++) > csa[i]->pn = i; > @@ -2059,31 +2057,6 @@ static void remove_tasks_in_empty_cpuset(struct cpuset > *cs) > move_member_tasks_to_cpuset(cs, parent); > } > > -/* > - * Helper function to traverse cpusets. > - * It can be used to walk the cpuset tree from top to bottom, completing > - * one layer before dropping down to the next (thus always processing a > - * node before any of its children). > - */ > -static struct cpuset *cpuset_next(struct list_head *queue) > -{ > - struct cpuset *cp; > - struct cpuset *child; /* scans child cpusets of cp */ > - struct cgroup *cont; > - > - if (list_empty(queue)) > - return NULL; > - > - cp = list_first_entry(queue, struct cpuset, stack_list); > - list_del(queue->next); > - rcu_read_lock(); > - cpuset_for_each_child(child, cont, cp) > - list_add_tail(&child->stack_list, queue); > - rcu_read_unlock(); > - > - return cp; > -} > - > /** > * cpuset_propagate_hotplug_workfn - propagate CPU/memory hotplug to a cpuset > * @cs: cpuset in interest > @@ -2220,12 +2193,12 @@ static void cpuset_hotplug_workfn(struct work_struct > *work) > /* if cpus or mems went down, we need to propagate to descendants */ > if (cpus_offlined || mems_offlined) { > struct cpuset *cs; > - LIST_HEAD(queue); > + struct cgroup *pos_cgrp; > > - list_add_tail(&top_cpuset.stack_list, &queue); > - while ((cs = cpuset_next(&queue))) > - if (cs != &top_cpuset) > - schedule_cpuset_propagate_hotplug(cs); > + rcu_read_lock(); > + cpuset_for_each_descendant_pre(cs, pos_cgrp, &top_cpuset) > + schedule_cpuset_propagate_hotplug(cs); > + rcu_read_unlock(); > } > > mutex_unlock(&cpuset_mutex); > -- > 1.7.11.7 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
