From 505afcbd47a8588251409191dddd7f888b555c6f Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 12 Nov 2009 15:55:28 +0100 Subject: [PATCH] sched: Cleanup select_task_rq_fair() commit a50bde5130f65733142b32975616427d0ea50856 upstream Clean up the new affine to idle sibling bits while trying to grok them. Should not have any function differences. Signed-off-by: Peter Zijlstra Cc: Mike Galbraith LKML-Reference: <20091112145610.832503781@chello.nl> Signed-off-by: Ingo Molnar Signed-off-by: Mike Galbraith Signed-off-by: Greg Kroah-Hartman --- kernel/sched_fair.c | 73 +++++++++++++++++++++++++++++++-------------- 1 file changed, 51 insertions(+), 22 deletions(-) diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index 15a3182baeff..b5d2e72af4c8 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -1383,6 +1383,41 @@ find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu) return idlest; } +/* + * Try and locate an idle CPU in the sched_domain. + */ +static int +select_idle_sibling(struct task_struct *p, struct sched_domain *sd, int target) +{ + int cpu = smp_processor_id(); + int prev_cpu = task_cpu(p); + int i; + + /* + * If this domain spans both cpu and prev_cpu (see the SD_WAKE_AFFINE + * test in select_task_rq_fair) and the prev_cpu is idle then that's + * always a better target than the current cpu. + */ + if (target == cpu) { + if (!cpu_rq(prev_cpu)->cfs.nr_running) + target = prev_cpu; + } + + /* + * Otherwise, iterate the domain and find an elegible idle cpu. + */ + if (target == -1 || target == cpu) { + for_each_cpu_and(i, sched_domain_span(sd), &p->cpus_allowed) { + if (!cpu_rq(i)->cfs.nr_running) { + target = i; + break; + } + } + } + + return target; +} + /* * sched_balance_self: balance the current task (running on cpu) in domains * that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and @@ -1441,36 +1476,30 @@ select_task_rq_fair(struct rq *rq, struct task_struct *p, int sd_flag, int wake_ } if (want_affine && (tmp->flags & SD_WAKE_AFFINE)) { - int candidate = -1, i; + int target = -1; + /* + * If both cpu and prev_cpu are part of this domain, + * cpu is a valid SD_WAKE_AFFINE target. + */ if (cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) - candidate = cpu; + target = cpu; /* - * Check for an idle shared cache. + * If there's an idle sibling in this domain, make that + * the wake_affine target instead of the current cpu. + * + * XXX: should we possibly do this outside of + * WAKE_AFFINE, in case the shared cache domain is + * smaller than the WAKE_AFFINE domain? */ - if (tmp->flags & SD_PREFER_SIBLING) { - if (candidate == cpu) { - if (!cpu_rq(prev_cpu)->cfs.nr_running) - candidate = prev_cpu; - } - - if (candidate == -1 || candidate == cpu) { - for_each_cpu(i, sched_domain_span(tmp)) { - if (!cpumask_test_cpu(i, &p->cpus_allowed)) - continue; - if (!cpu_rq(i)->cfs.nr_running) { - candidate = i; - break; - } - } - } - } + if (tmp->flags & SD_PREFER_SIBLING) + target = select_idle_sibling(p, tmp, target); - if (candidate >= 0) { + if (target >= 0) { affine_sd = tmp; want_affine = 0; - cpu = candidate; + cpu = target; } } -- 2.39.5