sched: More generic WAKE_AFFINE vs select_idle_sibling()

Instead of only considering SD_WAKE_AFFINE | SD_PREFER_SIBLING
domains also allow all SD_PREFER_SIBLING domains below a
SD_WAKE_AFFINE domain to change the affinity target.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <20091112145610.909723612@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index a32df15247461f6edef4238a854ad5390c75ebb8..f28a2671a1a66bda87ed1b217f65c8bf9459c820 100644 (file)
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1333,20 +1333,16 @@ select_idle_sibling(struct task_struct *p, struct sched_domain *sd, int target)
         * 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;
-       }
+       if (target == cpu && !cpu_rq(prev_cpu)->cfs.nr_running)
+               return 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;
-                       }
+       for_each_cpu_and(i, sched_domain_span(sd), &p->cpus_allowed) {
+               if (!cpu_rq(i)->cfs.nr_running) {
+                       target = i;
+                       break;
                }
        }
 
@@ -1407,7 +1403,12 @@ static int select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flag
                                want_sd = 0;
                }
 
-               if (want_affine && (tmp->flags & SD_WAKE_AFFINE)) {
+               /*
+                * While iterating the domains looking for a spanning
+                * WAKE_AFFINE domain, adjust the affine target to any idle cpu
+                * in cache sharing domains along the way.
+                */
+               if (want_affine) {
                        int target = -1;
 
                        /*
@@ -1420,17 +1421,15 @@ static int select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flag
                        /*
                         * 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)
                                target = select_idle_sibling(p, tmp, target);
 
                        if (target >= 0) {
-                               affine_sd = tmp;
-                               want_affine = 0;
+                               if (tmp->flags & SD_WAKE_AFFINE) {
+                                       affine_sd = tmp;
+                                       want_affine = 0;
+                               }
                                cpu = target;
                        }
                }