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Date: Tue, 26 Mar 2013 15:01:40 +0900 From: Joonsoo Kim <iamjoonsoo.kim@....com> To: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org> Cc: linux-kernel@...r.kernel.org, Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>, Joonsoo Kim <iamjoonsoo.kim@....com> Subject: [PATCH v2 6/6] sched: prevent to re-select dst-cpu in load_balance() Commit 88b8dac0 makes load_balance() consider other cpus in its group. But, in that, there is no code for preventing to re-select dst-cpu. So, same dst-cpu can be selected over and over. This patch add functionality to load_balance() in order to exclude cpu which is selected once. We prevent to re-select dst_cpu via env's cpus, so now, env's cpus is a candidate not only for src_cpus, but also dst_cpus. Cc: Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index e3f09f4..6f238d2 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3883,7 +3883,7 @@ int can_migrate_task(struct task_struct *p, struct lb_env *env) return 0; if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) { - int new_dst_cpu; + int cpu; schedstat_inc(p, se.statistics.nr_failed_migrations_affine); @@ -3898,12 +3898,14 @@ int can_migrate_task(struct task_struct *p, struct lb_env *env) if (!env->dst_grpmask || (env->flags & LBF_SOME_PINNED)) return 0; - new_dst_cpu = cpumask_first_and(env->dst_grpmask, - tsk_cpus_allowed(p)); - if (new_dst_cpu < nr_cpu_ids) { - env->flags |= LBF_SOME_PINNED; - env->new_dst_cpu = new_dst_cpu; - } + /* Prevent to re-select dst_cpu via env's cpus */ + for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) + if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) { + env->flags |= LBF_SOME_PINNED; + env->new_dst_cpu = cpu; + break; + } + return 0; } @@ -4989,7 +4991,6 @@ static int load_balance(int this_cpu, struct rq *this_rq, int *balance) { int ld_moved, cur_ld_moved, active_balance = 0; - int lb_iterations, max_lb_iterations; struct sched_group *group; struct rq *busiest; unsigned long flags; @@ -5009,11 +5010,6 @@ static int load_balance(int this_cpu, struct rq *this_rq, * other cpus in our group */ if (idle == CPU_NEWLY_IDLE) { env.dst_grpmask = NULL; - /* we don't care max_lb_iterations in this case, - * in following patch, this will be removed */ - max_lb_iterations = 0; - } else { - max_lb_iterations = cpumask_weight(env.dst_grpmask); } cpumask_copy(cpus, cpu_active_mask); @@ -5041,7 +5037,6 @@ redo: schedstat_add(sd, lb_imbalance[idle], env.imbalance); ld_moved = 0; - lb_iterations = 1; if (busiest->nr_running > 1) { /* * Attempt to move tasks. If find_busiest_group has found @@ -5098,14 +5093,17 @@ more_balance: * moreover subsequent load balance cycles should correct the * excess load moved. */ - if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0 && - lb_iterations++ < max_lb_iterations) { + if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0) { env.dst_rq = cpu_rq(env.new_dst_cpu); env.dst_cpu = env.new_dst_cpu; env.flags &= ~LBF_SOME_PINNED; env.loop = 0; env.loop_break = sched_nr_migrate_break; + + /* Prevent to re-select dst_cpu via env's cpus */ + cpumask_clear_cpu(env.dst_cpu, env.cpus); + /* * Go back to "more_balance" rather than "redo" since we * need to continue with same src_cpu. -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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