sched: Merge select_task_rq_fair() and sched_balance_self()

The problem with wake_idle() is that is doesn't respect things like
cpu_power, which means it doesn't deal well with SMT nor the recent
RT interaction.

To cure this, it needs to do what sched_balance_self() does, which
leads to the possibility of merging select_task_rq_fair() and
sched_balance_self().

Modify sched_balance_self() to:

  - update_shares() when walking up the domain tree,
    (it only called it for the top domain, but it should
     have done this anyway), which allows us to remove
    this ugly bit from try_to_wake_up().

  - do wake_affine() on the smallest domain that contains
    both this (the waking) and the prev (the wakee) cpu for
    WAKE invocations.

Then use the top-down balance steps it had to replace wake_idle().

This leads to the dissapearance of SD_WAKE_BALANCE and
SD_WAKE_IDLE_FAR, with SD_WAKE_IDLE replaced with SD_BALANCE_WAKE.

SD_WAKE_AFFINE needs SD_BALANCE_WAKE to be effective.

Touch all topology bits to replace the old with new SD flags --
platforms might need re-tuning, enabling SD_BALANCE_WAKE
conditionally on a NUMA distance seems like a good additional
feature, magny-core and small nehalem systems would want this
enabled, systems with slow interconnects would not.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 3 insertions, 38 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index fc6fda881d2e..6c819f338b11 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -512,14 +512,6 @@ struct root_domain {
 #ifdef CONFIG_SMP
         struct cpupri cpupri;
 #endif
-#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
-        /*
-         * Preferred wake up cpu nominated by sched_mc balance that will be
-         * used when most cpus are idle in the system indicating overall very
-         * low system utilisation. Triggered at POWERSAVINGS_BALANCE_WAKEUP(2)
-         */
-        unsigned int sched_mc_preferred_wakeup_cpu;
-#endif
 };
 
 /*
@@ -2315,22 +2307,6 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync)
         if (!sched_feat(SYNC_WAKEUPS))
                 sync = 0;
 
-#ifdef CONFIG_SMP
-        if (sched_feat(LB_WAKEUP_UPDATE) && !root_task_group_empty()) {
-                struct sched_domain *sd;
-
-                this_cpu = raw_smp_processor_id();
-                cpu = task_cpu(p);
-
-                for_each_domain(this_cpu, sd) {
-                        if (cpumask_test_cpu(cpu, sched_domain_span(sd))) {
-                                update_shares(sd);
-                                break;
-                        }
-                }
-        }
-#endif
-
         this_cpu = get_cpu();
 
         smp_wmb();
@@ -3533,11 +3509,6 @@ static inline int check_power_save_busiest_group(struct sd_lb_stats *sds,
         *imbalance = sds->min_load_per_task;
         sds->busiest = sds->group_min;
 
-        if (sched_mc_power_savings >= POWERSAVINGS_BALANCE_WAKEUP) {
-                cpu_rq(this_cpu)->rd->sched_mc_preferred_wakeup_cpu =
-                        group_first_cpu(sds->group_leader);
-        }
-
         return 1;
 
 }
@@ -7850,9 +7821,7 @@ static int sd_degenerate(struct sched_domain *sd)
         }
 
         /* Following flags don't use groups */
-        if (sd->flags & (SD_WAKE_IDLE |
-                         SD_WAKE_AFFINE |
-                         SD_WAKE_BALANCE))
+        if (sd->flags & (SD_WAKE_AFFINE))
                 return 0;
 
         return 1;
@@ -7869,10 +7838,6 @@ sd_parent_degenerate(struct sched_domain *sd, struct sched_domain *parent)
         if (!cpumask_equal(sched_domain_span(sd), sched_domain_span(parent)))
                 return 0;
 
-        /* Does parent contain flags not in child? */
-        /* WAKE_BALANCE is a subset of WAKE_AFFINE */
-        if (cflags & SD_WAKE_AFFINE)
-                pflags &= ~SD_WAKE_BALANCE;
         /* Flags needing groups don't count if only 1 group in parent */
         if (parent->groups == parent->groups->next) {
                 pflags &= ~(SD_LOAD_BALANCE |
@@ -8558,10 +8523,10 @@ static void set_domain_attribute(struct sched_domain *sd,
                 request = attr->relax_domain_level;
         if (request < sd->level) {
                 /* turn off idle balance on this domain */
-                sd->flags &= ~(SD_WAKE_IDLE|SD_BALANCE_NEWIDLE);
+                sd->flags &= ~(SD_BALANCE_WAKE|SD_BALANCE_NEWIDLE);
         } else {
                 /* turn on idle balance on this domain */
-                sd->flags |= (SD_WAKE_IDLE_FAR|SD_BALANCE_NEWIDLE);
+                sd->flags |= (SD_BALANCE_WAKE|SD_BALANCE_NEWIDLE);
         }
 }