From 470fd646444c65a5d062a371f5ec8dcedee61239 Mon Sep 17 00:00:00 2001 From: Cliff Wickman Date: Thu, 18 Oct 2007 23:40:46 -0700 Subject: hotplug cpu: migrate a task within its cpuset When a cpu is disabled, move_task_off_dead_cpu() is called for tasks that have been running on that cpu. Currently, such a task is migrated: 1) to any cpu on the same node as the disabled cpu, which is both online and among that task's cpus_allowed 2) to any cpu which is both online and among that task's cpus_allowed It is typical of a multithreaded application running on a large NUMA system to have its tasks confined to a cpuset so as to cluster them near the memory that they share. Furthermore, it is typical to explicitly place such a task on a specific cpu in that cpuset. And in that case the task's cpus_allowed includes only a single cpu. This patch would insert a preference to migrate such a task to some cpu within its cpuset (and set its cpus_allowed to its entire cpuset). With this patch, migrate the task to: 1) to any cpu on the same node as the disabled cpu, which is both online and among that task's cpus_allowed 2) to any online cpu within the task's cpuset 3) to any cpu which is both online and among that task's cpus_allowed In order to do this, move_task_off_dead_cpu() must make a call to cpuset_cpus_allowed_locked(), a new subset of cpuset_cpus_allowed(), that will not block. (name change - per Oleg's suggestion) Calls are made to cpuset_lock() and cpuset_unlock() in migration_call() to set the cpuset mutex during the whole migrate_live_tasks() and migrate_dead_tasks() procedure. [akpm@linux-foundation.org: build fix] [pj@sgi.com: Fix indentation and spacing] Signed-off-by: Cliff Wickman Cc: Oleg Nesterov Cc: Christoph Lameter Cc: Paul Jackson Cc: Ingo Molnar Signed-off-by: Paul Jackson Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/cpuset.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include/linux') diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h index 31adfde1c95f..ecae585ec3da 100644 --- a/include/linux/cpuset.h +++ b/include/linux/cpuset.h @@ -21,6 +21,7 @@ extern int cpuset_init_early(void); extern int cpuset_init(void); extern void cpuset_init_smp(void); extern cpumask_t cpuset_cpus_allowed(struct task_struct *p); +extern cpumask_t cpuset_cpus_allowed_locked(struct task_struct *p); extern nodemask_t cpuset_mems_allowed(struct task_struct *p); #define cpuset_current_mems_allowed (current->mems_allowed) void cpuset_init_current_mems_allowed(void); @@ -87,6 +88,10 @@ static inline cpumask_t cpuset_cpus_allowed(struct task_struct *p) { return cpu_possible_map; } +static inline cpumask_t cpuset_cpus_allowed_locked(struct task_struct *p) +{ + return cpu_possible_map; +} static inline nodemask_t cpuset_mems_allowed(struct task_struct *p) { -- cgit v1.2.2