Query for Cliff:

1) Can we narrow the scope of callback_mutex in scan_for_empty_cpusets()?

2) Can we avoid rewriting the cpus, mems of cpusets except when it is
   likely that we'll be changing them?

3) Should not remove_tasks_in_empty_cpuset() also check for empty mems?

-pj

---

 kernel/cpuset.c |   21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

--- 2.6.24-rc6-mm1.orig/kernel/cpuset.c 2008-01-12 22:04:08.027821401 -0800
+++ 2.6.24-rc6-mm1/kernel/cpuset.c      2008-01-12 22:10:30.701745078 -0800
@@ -1751,7 +1751,8 @@ static void remove_tasks_in_empty_cpuset
         * has online cpus, so can't be empty).
         */
        parent = cs->parent;
-       while (cpus_empty(parent->cpus_allowed))
+       while (cpus_empty(parent->cpus_allowed) ||
+                       nodes_empty(parent->mems_allowed))
                parent = parent->parent;
 
        move_member_tasks_to_cpuset(cs, parent);
@@ -1783,7 +1784,6 @@ static void scan_for_empty_cpusets(const
 
        list_add_tail((struct list_head *)&root->stack_list, &queue);
 
-       mutex_lock(&callback_mutex);
        while (!list_empty(&queue)) {
                cp = container_of(queue.next, struct cpuset, stack_list);
                list_del(queue.next);
@@ -1792,19 +1792,24 @@ static void scan_for_empty_cpusets(const
                        list_add_tail(&child->stack_list, &queue);
                }
                cont = cp->css.cgroup;
+
+               /* Continue past cpusets with all cpus, mems online */
+               if (cpus_subset(cp->cpus_allowed, cpu_online_map) &&
+                   nodes_subset(cp->mems_allowed, node_states[N_HIGH_MEMORY]))
+                       continue;
+
                /* Remove offline cpus and mems from this cpuset. */
+               mutex_lock(&callback_mutex);
                cpus_and(cp->cpus_allowed, cp->cpus_allowed, cpu_online_map);
                nodes_and(cp->mems_allowed, cp->mems_allowed,
                                                node_states[N_HIGH_MEMORY]);
+               mutex_unlock(&callback_mutex);
+
+               /* Move tasks from the empty cpuset to a parent */
                if (cpus_empty(cp->cpus_allowed) ||
-                    nodes_empty(cp->mems_allowed)) {
-                       /* Move tasks from the empty cpuset to a parent */
-                       mutex_unlock(&callback_mutex);
+                    nodes_empty(cp->mems_allowed))
                        remove_tasks_in_empty_cpuset(cp);
-                       mutex_lock(&callback_mutex);
-               }
        }
-       mutex_unlock(&callback_mutex);
 }
 
 /*

-- 
                          I won't rest till it's the best ...
                          Programmer, Linux Scalability
                          Paul Jackson <[EMAIL PROTECTED]> 1.650.933.1373
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