From 4dcfe1025b513c2c1da5bf5586adb0e80148f612 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 10 Nov 2011 13:01:10 +0100 Subject: [PATCH] sched: Avoid SMT siblings in select_idle_sibling() if possible Avoid select_idle_sibling() from picking a sibling thread if there's an idle core that shares cache. This fixes SMT balancing in the increasingly common case where there's a shared cache core available to balance to. Tested-by: Mike Galbraith Signed-off-by: Peter Zijlstra Cc: Suresh Siddha Link: http://lkml.kernel.org/r/1321350377.1421.55.camel@twins Signed-off-by: Ingo Molnar --- kernel/sched_fair.c | 42 ++++++++++++++++++++++++++++-------------- 1 file changed, 28 insertions(+), 14 deletions(-) diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index 7e51b5b..ba0e1f4 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -2326,7 +2326,8 @@ static int select_idle_sibling(struct task_struct *p, int target) int cpu = smp_processor_id(); int prev_cpu = task_cpu(p); struct sched_domain *sd; - int i; + struct sched_group *sg; + int i, smt = 0; /* * If the task is going to be woken-up on this cpu and if it is @@ -2346,25 +2347,38 @@ static int select_idle_sibling(struct task_struct *p, int target) * Otherwise, iterate the domains and find an elegible idle cpu. */ rcu_read_lock(); +again: for_each_domain(target, sd) { - if (!(sd->flags & SD_SHARE_PKG_RESOURCES)) - break; + if (!smt && (sd->flags & SD_SHARE_CPUPOWER)) + continue; - for_each_cpu_and(i, sched_domain_span(sd), tsk_cpus_allowed(p)) { - if (idle_cpu(i)) { - target = i; - break; + if (!(sd->flags & SD_SHARE_PKG_RESOURCES)) { + if (!smt) { + smt = 1; + goto again; } + break; } - /* - * Lets stop looking for an idle sibling when we reached - * the domain that spans the current cpu and prev_cpu. - */ - if (cpumask_test_cpu(cpu, sched_domain_span(sd)) && - cpumask_test_cpu(prev_cpu, sched_domain_span(sd))) - break; + sg = sd->groups; + do { + if (!cpumask_intersects(sched_group_cpus(sg), + tsk_cpus_allowed(p))) + goto next; + + for_each_cpu(i, sched_group_cpus(sg)) { + if (!idle_cpu(i)) + goto next; + } + + target = cpumask_first_and(sched_group_cpus(sg), + tsk_cpus_allowed(p)); + goto done; +next: + sg = sg->next; + } while (sg != sd->groups); } +done: rcu_read_unlock(); return target; -- 2.7.4