diff options
| -rw-r--r-- | include/linux/cpumask.h | 7 | ||||
| -rw-r--r-- | kernel/sched/core.c | 7 | ||||
| -rw-r--r-- | lib/cpumask.c | 29 |
3 files changed, 42 insertions, 1 deletions
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h index d5cc88514aee..f0d895d6ac39 100644 --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h @@ -194,6 +194,11 @@ static inline unsigned int cpumask_local_spread(unsigned int i, int node) return 0; } +static inline int cpumask_any_and_distribute(const struct cpumask *src1p, + const struct cpumask *src2p) { + return cpumask_next_and(-1, src1p, src2p); +} + #define for_each_cpu(cpu, mask) \ for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask) #define for_each_cpu_not(cpu, mask) \ @@ -245,6 +250,8 @@ static inline unsigned int cpumask_next_zero(int n, const struct cpumask *srcp) int cpumask_next_and(int n, const struct cpumask *, const struct cpumask *); int cpumask_any_but(const struct cpumask *mask, unsigned int cpu); unsigned int cpumask_local_spread(unsigned int i, int node); +int cpumask_any_and_distribute(const struct cpumask *src1p, + const struct cpumask *src2p); /** * for_each_cpu - iterate over every cpu in a mask diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 978bf6f6e0ff..014d4f793313 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1650,7 +1650,12 @@ static int __set_cpus_allowed_ptr(struct task_struct *p, if (cpumask_equal(p->cpus_ptr, new_mask)) goto out; - dest_cpu = cpumask_any_and(cpu_valid_mask, new_mask); + /* + * Picking a ~random cpu helps in cases where we are changing affinity + * for groups of tasks (ie. cpuset), so that load balancing is not + * immediately required to distribute the tasks within their new mask. + */ + dest_cpu = cpumask_any_and_distribute(cpu_valid_mask, new_mask); if (dest_cpu >= nr_cpu_ids) { ret = -EINVAL; goto out; diff --git a/lib/cpumask.c b/lib/cpumask.c index 0cb672eb107c..fb22fb266f93 100644 --- a/lib/cpumask.c +++ b/lib/cpumask.c @@ -232,3 +232,32 @@ unsigned int cpumask_local_spread(unsigned int i, int node) BUG(); } EXPORT_SYMBOL(cpumask_local_spread); + +static DEFINE_PER_CPU(int, distribute_cpu_mask_prev); + +/** + * Returns an arbitrary cpu within srcp1 & srcp2. + * + * Iterated calls using the same srcp1 and srcp2 will be distributed within + * their intersection. + * + * Returns >= nr_cpu_ids if the intersection is empty. + */ +int cpumask_any_and_distribute(const struct cpumask *src1p, + const struct cpumask *src2p) +{ + int next, prev; + + /* NOTE: our first selection will skip 0. */ + prev = __this_cpu_read(distribute_cpu_mask_prev); + + next = cpumask_next_and(prev, src1p, src2p); + if (next >= nr_cpu_ids) + next = cpumask_first_and(src1p, src2p); + + if (next < nr_cpu_ids) + __this_cpu_write(distribute_cpu_mask_prev, next); + + return next; +} +EXPORT_SYMBOL(cpumask_any_and_distribute); |