Messages in this thread Patch in this message |  | | | From | "Srivatsa S. Bhat" <> | | Subject | [PATCH v5 2/5] cpusets, hotplug: Implement cpuset tree traversal in a helper function | | Date | Thu, 17 May 2012 22:30:17 +0530 |
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At present, the functions that deal with cpusets during CPU/Mem hotplug are quite messy, since a lot of the functionality is mixed up without clear separation. And this takes a toll on optimization as well. For example, the function cpuset_update_active_cpus() is called on both CPU offline and CPU online events; and it invokes scan_for_empty_cpusets(), which makes sense only for CPU offline events. And hence, the current code ends up unnecessarily traversing the cpuset tree during CPU online also.
As a first step towards cleaning up those functions, encapsulate the cpuset tree traversal in a helper function, so as to facilitate upcoming changes.
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> --- kernel/cpuset.c | 36 +++++++++++++++++++++++++++--------- 1 files changed, 27 insertions(+), 9 deletions(-) diff --git a/kernel/cpuset.c b/kernel/cpuset.c index 5fc1570..15926f8 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -2001,6 +2001,32 @@ static void remove_tasks_in_empty_cpuset(struct cpuset *cs) } /* + * 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); + list_for_each_entry(cont, &cp->css.cgroup->children, sibling) { + child = cgroup_cs(cont); + list_add_tail(&child->stack_list, queue); + } + + return cp; +} + + +/* * Walk the specified cpuset subtree and look for empty cpusets. * The tasks of such cpuset must be moved to a parent cpuset. * @@ -2019,19 +2045,11 @@ static void scan_for_empty_cpusets(struct cpuset *root) { LIST_HEAD(queue); struct cpuset *cp; /* scans cpusets being updated */ - struct cpuset *child; /* scans child cpusets of cp */ - struct cgroup *cont; static nodemask_t oldmems; /* protected by cgroup_mutex */ list_add_tail((struct list_head *)&root->stack_list, &queue); - while (!list_empty(&queue)) { - cp = list_first_entry(&queue, struct cpuset, stack_list); - list_del(queue.next); - list_for_each_entry(cont, &cp->css.cgroup->children, sibling) { - child = cgroup_cs(cont); - list_add_tail(&child->stack_list, &queue); - } + while ((cp = cpuset_next(&queue)) != NULL) { /* Continue past cpusets with all cpus, mems online */ if (cpumask_subset(cp->cpus_allowed, cpu_active_mask) &&
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