cpuset: speed up sched domain partition

All child cpusets contain a subset of the parent's cpus, so we can skip
them when partitioning sched domains. This decreases 'csa' greately for
cpusets with multi-level hierarchy.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 37 insertions, 4 deletions

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 3624dc0e95ed..c818c36b0c5f 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -486,13 +486,38 @@ static int cpusets_overlap(struct cpuset *a, struct cpuset *b)
 static void
 update_domain_attr(struct sched_domain_attr *dattr, struct cpuset *c)
 {
-        if (!dattr)
-                return;
         if (dattr->relax_domain_level < c->relax_domain_level)
                 dattr->relax_domain_level = c->relax_domain_level;
         return;
 }
 
+static void
+update_domain_attr_tree(struct sched_domain_attr *dattr, struct cpuset *c)
+{
+        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);
+
+                if (cpus_empty(cp->cpus_allowed))
+                        continue;
+
+                if (is_sched_load_balance(cp))
+                        update_domain_attr(dattr, cp);
+
+                list_for_each_entry(cont, &cp->css.cgroup->children, sibling) {
+                        child = cgroup_cs(cont);
+                        list_add_tail(&child->stack_list, &q);
+                }
+        }
+}
+
 /*
  * rebuild_sched_domains()
  *
@@ -614,8 +639,16 @@ void rebuild_sched_domains(void)
                 if (cpus_empty(cp->cpus_allowed))
                         continue;
 
-                if (is_sched_load_balance(cp))
+                /*
+                 * 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;
+                        continue;
+                }
 
                 list_for_each_entry(cont, &cp->css.cgroup->children, sibling) {
                         child = cgroup_cs(cont);
@@ -686,7 +719,7 @@ restart:
                                         cpus_or(*dp, *dp, b->cpus_allowed);
                                         b->pn = -1;
                                         if (dattr)
-                                                update_domain_attr(dattr
+                                                update_domain_attr_tree(dattr
                                                                    + nslot, b);
                                 }
                         }