task_numa_find_cpu helps to find the cpu to swap/move the task. Its guarded by numa_has_capacity(). However node not having capacity shouldn't deter a task swapping if it helps numa placement.
Further load_too_imbalanced, which evaluates possibilities of move/swap, provides similar checks as numa_has_capacity. Hence remove numa_has_capacity() to enhance possibilities of task swapping even if load is imbalanced. Running SPECjbb2005 on a 4 node machine and comparing bops/JVM JVMS LAST_PATCH WITH_PATCH %CHANGE 16 25657.9 25804.1 0.569 1 74435 73413 -1.37 Acked-by: Rik van Riel <[email protected]> Signed-off-by: Srikar Dronamraju <[email protected]> --- kernel/sched/fair.c | 36 +++--------------------------------- 1 file changed, 3 insertions(+), 33 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 87fb20e..10b6886 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1417,7 +1417,6 @@ struct numa_stats { unsigned long compute_capacity; unsigned int nr_running; - int has_free_capacity; }; /* @@ -1444,8 +1443,7 @@ static void update_numa_stats(struct numa_stats *ns, int nid) * the @ns structure is NULL'ed and task_numa_compare() will * not find this node attractive. * - * We'll either bail at !has_free_capacity, or we'll detect a huge - * imbalance and bail there. + * We'll detect a huge imbalance and bail there. */ if (!cpus) return; @@ -1456,7 +1454,6 @@ static void update_numa_stats(struct numa_stats *ns, int nid) capacity = min_t(unsigned, capacity, DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE)); - ns->has_free_capacity = (ns->nr_running < capacity); } struct task_numa_env { @@ -1683,31 +1680,6 @@ static void task_numa_find_cpu(struct task_numa_env *env, } } -/* Only move tasks to a NUMA node less busy than the current node. */ -static bool numa_has_capacity(struct task_numa_env *env) -{ - struct numa_stats *src = &env->src_stats; - struct numa_stats *dst = &env->dst_stats; - - if (src->has_free_capacity && !dst->has_free_capacity) - return false; - - /* - * Only consider a task move if the source has a higher load - * than the destination, corrected for CPU capacity on each node. - * - * src->load dst->load - * --------------------- vs --------------------- - * src->compute_capacity dst->compute_capacity - */ - if (src->load * dst->compute_capacity * env->imbalance_pct > - - dst->load * src->compute_capacity * 100) - return true; - - return false; -} - static int task_numa_migrate(struct task_struct *p) { struct task_numa_env env = { @@ -1763,8 +1735,7 @@ static int task_numa_migrate(struct task_struct *p) update_numa_stats(&env.dst_stats, env.dst_nid); /* Try to find a spot on the preferred nid. */ - if (numa_has_capacity(&env)) - task_numa_find_cpu(&env, taskimp, groupimp); + task_numa_find_cpu(&env, taskimp, groupimp); /* * Look at other nodes in these cases: @@ -1794,8 +1765,7 @@ static int task_numa_migrate(struct task_struct *p) env.dist = dist; env.dst_nid = nid; update_numa_stats(&env.dst_stats, env.dst_nid); - if (numa_has_capacity(&env)) - task_numa_find_cpu(&env, taskimp, groupimp); + task_numa_find_cpu(&env, taskimp, groupimp); } } -- 1.8.3.1
