The patch titled
sched: fix evaluation of skip_for_load in move_tasks()
has been added to the -mm tree. Its filename is
sched-avoid-unnecessarily-moving-highest-priority-task-move_tasks-fix-2.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
From: Peter Williams <pwil3058@xxxxxxxxxxxxxx>
Problem:
In the patch
sched-avoid-unnecessarily-moving-highest-priority-task-move_tasks.patch I
got a the sense of a boolean expression wrong when assigning a value to
skip_for_load. The expression should have been negated before being
assigned.
Additionally, busiest_best_prio_seen is being set when tasks are moved
instead of when they are skipped which will cause problems when the current
task does not have prio=busiest_best_prio.
Solution:
Negate the expression and apply de Marcos rule to simplify it and move the
setting of busiest_best_prio_seen.
Signed-off-by: Peter Williams <pwil3058@xxxxxxxxxxxxxx>
Cc: "Siddha, Suresh B" <suresh.b.siddha@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
kernel/sched.c | 10 ++++++----
1 files changed, 6 insertions(+), 4 deletions(-)
diff -puN kernel/sched.c~sched-avoid-unnecessarily-moving-highest-priority-task-move_tasks-fix-2 kernel/sched.c
--- devel/kernel/sched.c~sched-avoid-unnecessarily-moving-highest-priority-task-move_tasks-fix-2 2006-04-24 20:38:20.000000000 -0700
+++ devel-akpm/kernel/sched.c 2006-04-24 20:38:20.000000000 -0700
@@ -2010,7 +2010,10 @@ static int move_tasks(runqueue_t *this_r
busiest_best_prio = rq_best_prio(busiest);
/*
* Enable handling of the case where there is more than one task
- * with the best priority.
+ * with the best priority. If the current running task is one
+ * of those with prio==busiest_best_prio we know it won't be moved
+ * and therefore it's safe to override the skip (based on load) of
+ * any task we find with that prio.
*/
busiest_best_prio_seen = busiest_best_prio == busiest->curr->prio;
@@ -2059,9 +2062,10 @@ skip_queue:
*/
skip_for_load = tmp->load_weight > rem_load_move;
if (skip_for_load && idx < this_best_prio)
- skip_for_load = busiest_best_prio_seen || idx != busiest_best_prio;
+ skip_for_load = !busiest_best_prio_seen && idx == busiest_best_prio;
if (skip_for_load ||
!can_migrate_task(tmp, busiest, this_cpu, sd, idle, &pinned)) {
+ busiest_best_prio_seen |= idx == busiest_best_prio;
if (curr != head)
goto skip_queue;
idx++;
@@ -2084,8 +2088,6 @@ skip_queue:
if (pulled < max_nr_move && rem_load_move > 0) {
if (idx < this_best_prio)
this_best_prio = idx;
- if (idx == busiest_best_prio)
- busiest_best_prio_seen = 1;
if (curr != head)
goto skip_queue;
idx++;
_
Patches currently in -mm which might be from pwil3058@xxxxxxxxxxxxxx are
sched-implement-smpnice.patch
sched-protect-calculation-of-max_pull-from-integer-wrap.patch
sched-store-weighted-load-on-up.patch
sched-prevent-high-load-weight-tasks-suppressing-balancing.patch
sched-improve-stability-of-smpnice-load-balancing.patch
sched-improve-smpnice-load-balancing-when-load-per-task.patch
sched-modify-move_tasks-to-improve-load-balancing-outcomes.patch
sched-avoid-unnecessarily-moving-highest-priority-task-move_tasks.patch
sched-avoid-unnecessarily-moving-highest-priority-task-move_tasks-fix-2.patch
sched-add-above-background-load-function.patch
-
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