diff options
author | Cliff Wickman <cpw@sgi.com> | 2007-10-19 06:40:46 (GMT) |
---|---|---|
committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-10-19 18:53:44 (GMT) |
commit | 470fd646444c65a5d062a371f5ec8dcedee61239 (patch) | |
tree | 59b923486d4a95efa07c4b2ad7cb0b1fcc3f3c88 /kernel/sched.c | |
parent | bd89aabc6761de1c35b154fe6f914a445d301510 (diff) | |
download | linux-fsl-qoriq-470fd646444c65a5d062a371f5ec8dcedee61239.tar.xz |
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 <cpw@sgi.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: Paul Jackson <pj@sgi.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/sched.c')
-rw-r--r-- | kernel/sched.c | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index a7e3046..4071306 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -5160,8 +5160,16 @@ static void move_task_off_dead_cpu(int dead_cpu, struct task_struct *p) /* No more Mr. Nice Guy. */ if (dest_cpu == NR_CPUS) { + cpumask_t cpus_allowed = cpuset_cpus_allowed_locked(p); + /* + * Try to stay on the same cpuset, where the + * current cpuset may be a subset of all cpus. + * The cpuset_cpus_allowed_locked() variant of + * cpuset_cpus_allowed() will not block. It must be + * called within calls to cpuset_lock/cpuset_unlock. + */ rq = task_rq_lock(p, &flags); - cpus_setall(p->cpus_allowed); + p->cpus_allowed = cpus_allowed; dest_cpu = any_online_cpu(p->cpus_allowed); task_rq_unlock(rq, &flags); @@ -5527,6 +5535,7 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu) case CPU_DEAD: case CPU_DEAD_FROZEN: + cpuset_lock(); /* around calls to cpuset_cpus_allowed_lock() */ migrate_live_tasks(cpu); rq = cpu_rq(cpu); kthread_stop(rq->migration_thread); @@ -5540,6 +5549,7 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu) rq->idle->sched_class = &idle_sched_class; migrate_dead_tasks(cpu); spin_unlock_irq(&rq->lock); + cpuset_unlock(); migrate_nr_uninterruptible(rq); BUG_ON(rq->nr_running != 0); |